electrical power transmission and distribution ... · pdf fileelectrical power transmission...

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KENYA STANDARD KS 1878-0:2010 ICS 29.240.01

© KEBS 2010 First Edition 2010

Electrical power transmission and distribution — Guidelines for the provision of electrical distribution networks in residential areas — Part 0: Definitions

BALLOT DRAFT, MAY 2010

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ii © KEBS 2010 — All rights reserved

TECHNICAL COMMITTEE REPRESENTATION The following organizations were represented on the Technical Committee: Nairobi City Council, City Engineer’s Department. Jomo Kenyatta University of Agriculture and Technology Kenya Polytechnic Kenya Power & Lighting Company Fluid & Power Systems Ltd Ministry of Public Works and Housing Ministry of Energy Kenafric Industries Ltd Power Technics Ltd Rural Electrification Authority The Energy Regulatory Commission Consumer Information Network Kenya Association of Manufacturers Institute of Engineers of Kenya Kenya Electricity Generating Company Ltd ABB LTD Switchgear & Controls Ltd Power Controls Ltd Communications Communication of Kenya Instrument Ltd Kenya Pipeline Company Ltd Telkom Kenya Ltd Meteorological Department Kenya Bureau of Standards — Secretariat

REVISION OF KENYA STANDARDS In order to keep abreast of progress in industry, Kenya standards shall be regularly reviewed. Suggestions for improvement to published standards, addressed to the Managing Director, Kenya Bureau of Standards, are welcome.

© Kenya Bureau of Standards, 2010 Copyright. Users are reminded that by virtue of Section 25 of the Copyright Act, Cap. 12 of 2001 of the Laws of Kenya, copyright subsists in all Kenya Standards and except as provided under Section 26 of this Act, no Kenya Standard produced by Kenya Bureau of Standards may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from the Managing Director.

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KENYA STANDARD KS 1878-0:2010 ICS 29.240.01

© KEBS 2010 — All rights reserved iii

Electrical power transmission and distribution — Guidelines for the provision of electrical distribution networks in residential areas — Part 0: Definitions

KENYA BUREAU OF STANDARDS (KEBS)

Head Office: P.O. Box 54974, Nairobi-00200, Tel.: (+254 020) 605490, 69028000, 602350, Mobile: 0722202137/8, 0734600471/2;

Fax: (+254 020) 604031 E-Mail: [email protected], Web:http://www.kebs.org

KEBS Coast Region P.O. Box 99376, Mombasa 80100 Tel: (+254 041) 229563, 230939/40 Fax: (+254 041) 229448 E-mail: [email protected]

KEBS Lake Region P.O. Box 2949, Kisumu 40100 Tel: (+254 057) 23549,22396 Fax: (+254 057) 21814 E-mail: [email protected]

KEBS North Rift Region P.O. Box 2138, Nakuru 20100 Tel: (+254 051) 210553, 210555

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iv © KEBS 2010 — All rights reserved

F O R E W O R D

This Kenya standard was prepared by the Switchgear and Distribution Equipment in accordance with the procedures of the Bureau and is in compliance with Annex 3 of the WTO/TB Agreement. The terms and definitions used in the electrical power supply are standardized in order to ensure uniform understanding while coordinating various functions. This is important for technical work, procurement, contracts, administrative, operation and maintenance of the residential electricity supply systems. In the development of this standard, SANS NRS 034-0:2001, Electricity distribution — guidelines for the provision of electrical distribution networks in residential areas — Part 0: Definitions, was extensively consulted. Assistance derived from this source is hereby acknowledged. Normative and informative annexes A 'normative' annex is an integral part of a standard, whereas an 'informative' annex is only for information and guidance. Summary of development

This Kenya Standard, having been prepared by the Communication Equipment Technical Committee was first approved by the National Standards Council in June 2010

Amendments issued since publication

Amd. No. Date Text affected

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KENYA STANDARD KS 1878-0:2010

© KEBS 2010 — All rights reserved 1

Electrical power transmission and distribution — Gu idelines for the provision of electrical distribution networks in re sidential areas — Part 0: Definitions 1 Scope This part of KS 1878 is a compilation of definitions used in the context of electrical distribution networks, and is intended as a reference applicable to all other parts of KS 1878. 2 Normative references The following referenced documents are indispensable for the application of this Kenya Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC, Multilingual dictionary of electricity, electronics and telecommunications KS 1859-1, High-voltage operating regulations — Part 1: Definitions — Preferred definitions for systems, equipment and conditions relating to the generation, transmission and distribution of electricity 3 Definitions "a" contact (make contact) a control or auxiliary contact that is closed when the main contacts of the mechanical switching device are closed and open when they are open account card a card which, when presented by a customer, automatically identifies the electricity account that the customer has with the electricity distributor accredited test authority an authority that is accepted by the Kenya Accreditation Service (KENAS) accuracy class a designation assigned to an instrument transformer, the current or voltage error and phase displacement of which remain within specified limits under prescribed conditions of use [IEC Dictionary] aerial bundled conductor (ABC) An aerial cable that consists of a group of insulated conductors laid-up together. In the case of a low-voltage ABC that uses a supporting core system, the supporting core can be bare or covered (see note). A medium-voltage ABC is supported by a separate steel catenary wire. NOTE Two types of construction of LV ABC are commonly used. One type comprises phase conductors supported by a neutral conductor, which can be bare or insulated. (This type, which is used in France, is commonly referred to as the French ABC system.) The other type of construction comprises conductors that are all equally supported by fittings. (This type of construction, called self-supporting ABC, is used in Germany, and is known as the German ABC system.) after diversity maximum demand (ADMD) The simultaneous maximum demand of a group of consumers divided by the number of consumers, expressed in kilovolt amperes. NOTE Characteristic ADMD: the value of the ADMD in a specific area of supply generally decreases to an approximate constant value for 1 000 consumers or more. This value is known as the characteristic ADMD. Where the ADMD is used with no mention of the number of consumers, it is assumed to be the characteristic ADMD, and is equal to the design ADMD. airbreak switch A device used for the purpose of connecting, sectionalizing or isolating equipment or sections of overhead line.

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2 © KEBS 2010 — All rights reserved

air mass A numerical value used to give an overall measure of the amount of atmosphere through which solar radiation has to pass. At sea level, when the sun is directly overhead, the air mass is 1.0. When the sun is lower in the sky (some hours from noon, or in winter months), the solar radiation has to cut through more atmosphere and the air mass is then higher than 1.0. all-aluminium alloy conductor (AAAC) A stranded conductor of which all wires are made of aluminium alloy. [IEC Dictionary] all-aluminium conductor (AAC) A stranded conductor of which all wires are made of aluminium. [IEC Dictionary] aluminium conductor steel reinforced (ACSR) A reinforced conductor with one or more layers of aluminium wires stranded around a core of galvanized steel wires. [IEC Dictionary] algorithm A precise and rigorous statement of a method of calculation. anchor A device, usually buried in the ground, so installed as to provide a firm point of attachment for resisting uplift. [IEC Dictionary] anchor rod A rod or other metallic element, connecting the stay, or guy, to the anchor. [IEC Dictionary] anti-climbing device A device installed on, or attached to, a support, structure, tower, guy, etc., to prevent climbing by unauthorized persons. apparent power The product of the measured root mean square (r.m.s.) a.c. current and the measured r.m.s. a.c. voltage, expressed in volt-amperes (VA). approval Acceptance, agreed to in writing, by the purchaser. approved Acceptable to and approved in writing by the purchaser. arcing distance The shortest distance in air external to the insulator between the metallic parts which normally have the operating voltage between them. [IEC Dictionary] armour A covering that consists of metal tape(s) or wires, generally used to protect the cable from external mechanical effects. armour clamp A fitting for gripping the armour of a cable at its termination to the gland body, and capable of retaining the armour in position for fault currents within the design parameters. armoured cable A cable provided with a wrapping of metal (usually tape or wire) for the purpose of mechanical protection. NOTE The armour can itself be covered with a protective sheath or serving. authentication A process used between a sender and a receiver, to ensure data integrity and origin integrity. authorized person A person who has been authorized, in writing, with defined authority and responsibilities.

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auto-recloser A mechanical switching device that, after opening, is capable of closing automatically after a predetermined time. NOTE Several redosures could occur before lock-out. "b" contact (break contact) A control or auxiliary contact that is open when the main contacts of the mechanical switching device are closed and closed when they are open backfill The soil removed during excavation and re-installed after the installation of the foundation back up protection Protection equipment or system which is intended to operate when a system fault is not cleared in due time because of inability or failure of the main protection to operate, or in the case of failure to operate of a circuit-breaker other than the associated circuit-breaker basic insulation level (BIL) A specific insulation level, expressed in kilovolts, in accordance with which the complete system (including the line pole insulation to earth at every pole, the switchgear, the line isolators and reclosers, and the substations connected to the system, including their transformers) is designed and constructed NOTE The BIL can refer to a complete system, such as a distribution network (including the line pole insulation to earth at every pole, the switchgear, the line isolators and reclosers, and the substations connected to the system, including their transformers) or to a single piece of equipment. Where the BIL is declared by a manufacturer as the impulse voltage level for which the equipment is designed, it is often referred to as the rated insulation level, or rated lightning impulse withstand voltage. baulk A concrete beam, attached, in a horizontal position, to the pole at a point or at points below ground level, to improve the stability of the pole under conditions where it is not practicable or possible to use stays. bay (of a substation) The part of a substation within which the switchgear and controlgear relating to a given circuit are contained. [605-02-09] NOTE According to the type of circuit, a substation may include: feeder bays, transformer bays, bus coupler bays, etc. bedding A cushioning layer or layers applied to a cable immediately beneath a metallic layer such as the armour or the reinforcement. beta (P) distribution A statistical distribution function that can be used to describe the electrical load of a group of consumers. binder A layer incorporated in a cable with the specific function of holding the components of the cable together within the layer. blinding Selected fine material used to completely cover an underground cable or pipe. blocking diode A diode (usually Schottky) used to prevent battery discharge through the photovoltaic array at night. NOTE 1 The blocking diode will also prevent damage to the regulator if the PV array is short circuited. NOTE 2 Blocking diodes are normally used in PV systems where the nominal voltage exceeds 24 V. bonding The low-impedance interconnection of conductor and equipment, to form an equipotential platform. branch line; spur feeder An electric line connected to a main line at a point on its route. [601 -02-10]

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NOTE A branch line which is a final circuit is called a spur. breaking load The tensile load applied during testing, and at which the cable breaks or becomes permanently deformed. burden (of an instrument transformer) The impedance of the secondary circuit. [IEC Dictionary] NOTE The burden is usually expressed as the apparent power absorbed by the secondary circuit at a specified power factor at the rated secondary current or voltage. busbar A low impedance conductor to which several electric circuits can be separately connected. bushing A device that enables one or more conductors to pass through a partition, such as a wall or a tank, and insulates the conductors from it. [IEC Dictionary] NOTE The means of attachment (flange or fixing device) to the partition forms part of the bushing. bus-coupler switchgear panel A switchgear panel that is used to open and close the electrical connection and provide safety isolation between two busbar systems of a switchboard with a double busbar configuration. It could include a switch-disconnector or a circuit-breaker. bus-section switchgear panel A switchgear panel that is used to open and close the electrical connection and provide safety isolation between two sections of busbar of a switchboard. It could include a switch-disconnector or a circuit-breaker. bypass diode A diode used to prevent damage to the photovoltaic module under partial shade conditions. cable A length of one or more insulated conductors with or without an overall protective covering. cable gland A device to seal and secure the sheath and to secure the armour (where provided) of an electric cable to the terminal equipment by means suitable for the type of the cable for which it is designed, including provision for making electrical connection to the sheath and to the armour. cable termination box A cable termination enclosure that can be used for either single-core or three-core cables. cable tie A component that has the specific purpose of holding together the cable cores which it surrounds. cable wiping gland A cable gland that has a wiping gland body. cipher A method of cryptography that applies an algorithm to the letters or digits of the plaintext to create ciphertext, and vice versa. NOTE Typically the algorithm is used in conjunction with one or more keys. circuit An arrangement of conductors and apparatus for the purpose of carrying electrical energy. circuit-breaker A mechanical switching device that is capable of making, carrying and breaking currents under normal circuit conditions, and also of making, carrying for a specified time and breaking currents under specified abnormal conditions, such as those of a short-circuit. (NRS 006(lnt):2000)

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circuit-breaker class B A circuit-breaker so designed as to not require maintenance of the interrupting parts of the main circuit during the expected operating life of the circuit-breaker, and only minimal maintenance of its other parts. NOTE Minimal maintenance might include aspects such as lubrication, replenishment of gas, and cleaning of external surfaces. circuit-breaker panel A switchgear panel complete with a fixed or withdrawable circuit-breaker. circuit-side The side of a circuit-breaker or switch that contains the cable or circuit connections, and that can be isolated from the busbars. common group; common supply group A supply group that associates a set of electricity dispensers on a geographical or regional basis, in which each and every electricity dispenser in the supply group has a common dispenser key. conductor Any wire, bar, tube or part of a cable intended to conduct electric current. conduit A pipe or trough, usually of metal or plastic, that is intended to protect wires against damage from external causes. continuous current of an arrester The current flowing through the arrester when energized at the continuous operating voltage. clamping voltage See residual voltage. clearance The shortest distance between two conductive parts, usually related to distance in air. closed loop breaking capacity The breaking current when opening a closed loop circuit, i.e. a circuit in which both sides of the switch remain alive after breaking and in which the voltage appearing across the terminals is substantially less than the system voltage. combined neutral and earth (CNE) A conductor that combines the functions of a neutral conductor and an earth conductor. communication core An insulated solid wire that is intended to carry data compacted conductor A stranded conductor in which the interstices between the component wires have been reduced by mechanical compression, or by drawing, or by suitable choice of the shape and disposition of wires. competent person A person who is in possession of a competency certificate for the classes of work in which he is deemed to be competent to work without constant supervision. completely self-protected (CSP) transformer A transformer that is designed to be self-protected against overloads, short-circuits and overheating compression jointing; crimped jointing a method of securing a connector to a conductor by using a special tool to produce permanent deformation of the connector and the conductor concentric cable a sheathed cable that has a phase core surrounded by a neutral-earth conductor that forms a single concentric layer around the phase core

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conductor any wire, bar or tube intended to conduct electric current conductor insulation insulation applied on a conductor or on a conductor screen connector A component that terminates conductors for the purpose of providing connection and disconnection to a suitable mating component. consumer A person who is supplied (or who is to be supplied) with electricity by an electricity supplier. consumer's earth terminal See earth terminal (consumer installation). consumer's installation The electrical apparatus under the control of a consumer on the consumer's premises. consumer's supply point See point of supply. conventional switching (lightning) impulse withstan d voltage The peak value of a switching (lightning) impulse test voltage at which an insulation shall not show any disruptive discharge when subjected to a specified number of applications of this impulse under specified conditions. This concept applies particularly to non-self-restoring insulations. NOTE This concept applies particularly to non-self-restoring insulations core An assembly that comprises a conductor with its own insulation (and screen, if any). covered conductor A conductor for use on overhead electrical distribution lines, that is covered with a thin layer of insulation, insufficient to provide full insulation for the applied voltage. creepage distance The shortest distance, along the surface of the insulating material, between two conductive parts. crimped jointing See compression jointing. cross-arm A component of a pole structure, usually horizontal, to which the line insulators are attached to provide the required clearance distance. cryptographic key A parameter used in conjunction with an algorithm for the purposes of validation, authentication, encipherment or decipherment. cryptography The discipline that embodies the principles, means and methods for the transformation of data in order to conceal its information content, or prevent its undetected modification, or prevent its unauthorized use (or any combination of these). cumulative distribution function (CDF) (of a sample of customers' loads) A function that gives the probability that the load sample will be less than or equal to a specific value of the load current. current rating (of cables) The rated normal current of a cable is the r.m.s. value of current that the cable can carry continuously under the specified conditions of use and behaviour.

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current transformer (CT) An instrument transformer in which the secondary current, in normal conditions of use, is substantially proportional to the primary current, and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections. [IEC Dictionary] customer A person (or legal entity) who either has entered into an electricity supply agreement with a licensee, or legally consumes electricity supplied by that licensee. cut-out See outdoor distribution cut-out. cut-out base The fixed part of a cut-out, provided with the contacts and terminals. cycle of battery A sequence of a discharge followed by a charge or a charge followed by a discharge under specified conditions. [IEV 486-03-20] data integrity The property that shows that data have not been altered or destroyed in an unauthorized manner. dead At or about zero potential and disconnected or isolated from any live power system. NOTE Rotating plant should not be regarded as dead until it is stationary or being slowly rotated by means of barring gear and it is not excited. dead time The time between the instant that the current is interrupted by the auto-recloser and the instant the contacts of the auto-recloser close as a result of automatic reclose operations. [IEC Dictionary] decipherment The cryptographic transformation of ciphertext data (see cryptography) to produce plaintext data; the reversal of encipherment. declared voltage The voltage declared by the utility as the voltage at the point of supply. default group See default supply group default supply group A supply group that associates a set of electricity dispensers which have not yet been allocated to a unique supply group or a common supply group, and in which each and every electricity dispenser in the supply group has a unique dispenser key. delayed protection operation A protection function that consists of a family of curves with operating times inversely proportional to the fault current as a multiple of the pick-up setting. designated person A person approved by the purchaser. designated range The range of conductor cross-sectional areas with which the fittings are intended to be used. design-data confidence level The level of confidence, expressed as a probability (p.u. or percentage), in the accuracy of the data used to estimate the ADMD and the slenderness factor for a particular group of customers. NOTE The opposite of design-data confidence level is design-data uncertainty level.

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design-data uncertainty level See design-data confidence level. design tension (of ABC) The statutory maximum load to which the ABC can be subjected developing network A network the construction of which has not yet reached the initially planned configuration, and from which temporary or early supply is made available to customers by agreement, in order to avoid delayed service availability dielectric A substance that can maintain a steady electric field and hence is an insulator differential relay An electrical measuring relay the characteristic quantity of which is the result of comparison of the input energizing quantities, either in magnitude or in phase and magnitude discharge voltage See residual voltage. discharge current of an arrester The impulse current, which flows through the arrester. [IEC 60099-4] discharge of battery An operation during which a battery delivers current to an external circuit by the conversion of chemical energy into electric energy disconnector A device on a surge arrester that will separate the earth tail connection from the arrester when the power-frequency current flowing through the arrester exceeds a specific value NOTE 1 A disconnector is capable of opening and closing a circuit either when negligible current is broken or made, or when no significant change in the voltage across the terminals of each of the poles of the disconnector occurs. It is also capable of carrying current under normal circuit conditions and carrying, for a specified time, currents under abnormal conditions such as those of short-circuit. NOTE 2 "Negligible current" implies currents such as capacitance currents of bushings, busbars, connections and very short lengths of cable, currents of permanently connected grading impedances of circuit-breakers and currents of voltage transformers and dividers. For rated voltages of 420 kV and below, a current not exceeding 0.5 A is deemed to be a negligible current for the purpose of this definition; for rated voltages exceeding 420 kV, the manufacturer should be consulted. NOTE 3 "No significant change in voltage" refers to such applications as the by-passing of induction voltage regulators or circuit-breakers. [IEC 60129 addition] discrimination (in protection) The ability of protection devices to disconnect only that section of a power system in which a fault has occurred. dispenser key A key associated with an electricity dispenser and used together with the standard transfer algorithm to encrypt tokens generated at a credit dispenser and to decrypt tokens input at an electricity dispenser. distortion (of waveform) A change in the form of the ideal waveform, usually by the addition of harmonics. distribution fuse cut-out A drop-out fuse comprising a fuse-base, a fuse-carrier lined with arc-quenching material, and a fuse-link having a flexible tail, and a small diameter arc-quenching tube surrounding the fuse-element distribution line See distributor. distribution network; distribution system

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All apparatus installed for the distribution of electrical energy. distribution of electricity The transfer of electricity to consumers within an area of consumption. [601-01-10] distribution transformer A voltage step-down transformer to supply a section of a distribution network with electrical energy. distribution undertaking An organization that supplies electricity to a group of consumers by means of a distribution system. [IEC Dictionary] NOTE The preferred term is "electricity supplier". distributor; distribution line A main low-voltage line or a main telecommunication line. diversity The lack of coincidence in the time of consumers' individual maximum demands. double earthing switches A pair of three-phase earthing switches, one fitted on each side of a disconnector. dressing of poles The attachment of hardware and accessories to poles. drop-out fuse-link assembly An assembly that comprises all components that form a complete device intended to protect equipment or parts of a distribution system (or both), in which the fuse-carrier automatically drops into a position that provides an isolating distance after the fuse has operated. dwelling A place or structure of residence. earth The conducting mass of the earth whose electrical potential at any point is conventionally taken as zero. [IEC Dictionary] earth connection A terminal or clamp at earth potential, to which all the equipment earth wires are connected and to which an earth electrode is connected externally. earth continuity conductor (ECC) A conductor that comprises a separate (bare or insulated) cable core or tinned hard-drawn copper wires in cable armour. earthed Connected to the general mass of earth in such a manner as to ensure, at all times, an immediate safe discharge of electrical energy. NOTE This definition applies only in respect of the supply authority. earth electrode A conductor or group of conductors in intimate contact with and providing an electrical connection to earth. earth fault A fault caused by a conductor being connected to earth or by the insulation resistance to earth becoming less than a specified value. [IEC Dictionary] earth fault factor (EFF) At a given location of a three-phase system, and for a given system configuration, the ratio of the highest r.m.s.phase-to-earth power frequency voltage on a healthy phase during a fault to earth affecting one or

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more phases at any point on the system to the r.m.s. phase-to-earth frequency voltage which would be obtained at the given location in the absence of any such fault. [IEV 604-03-06] earth fault factor (EFF) At a given location of a three-phase system, and for a given system configuration, the ratio of the highest r.m.s. phase-to-earth power-frequency voltage on a healthy phase during a fault to earth affecting one or more phases at any point on the system to the r.m.s. phase-to-earth frequency voltage which would be obtained at the given location in the absence of any such fault. [IEC Dictionary] earthing gear; earthing device A fixed or portable appliance used for earthing electrical apparatus. earthing position (of a withdrawable part) The position of a withdrawable part in which the closing of a mechanical switching device causes a main circuit to be short-circuited and earthed. earthing switch A mechanical switching device for earthing parts of a circuit, capable of withstanding for a specified time currents under abnormal conditions such as those of short-circuit, but not required to carry current under normal conditions of the circuit. [IEC Dictionary] NOTE 1 An earthing switch can have a short-circuit capacity. NOTE 2 An earthing switch can be incorporated into a disconnector. earth leakage current A current that flows to earth on account of imperfect insulation. NOTE In the context of a consumer's installation, an earth leakage current that would result in flow as a result of an insulation degradation on the electrical apparatus in the consumer's installation, or as a result of the bridging of insulation by any means, for example a consumer's making inadvertent contact with a live conductor or terminal. earth leakage protection A form of protection in which an earth leakage unit is used earth leakage unit A device that is capable of detecting the flow of a specified or predetermined current from a circuit to earth and of disconnecting automatically and reliably the affected circuit within a specified time when such current exceeds the specified or predetermined value. earth terminal (consumer installation) Any clamp or terminal at the point of supply by means of which the exposed conductive parts of the consumer's installation are connected to an earth electrode or to the supplier's protective conductor. earth terminal A terminal fitted on equipment and providing a means of connection for an earth conductor. [604-04-08] effectively earthed system An earthed system in which the power-frequency phase-to-earth overvoltages associated with earth faults are limited to 80 % of the highest phase-to-phase voltage of the system. efficiency (of inverter) The ratio of the output power at unity power factor to the input power which is the product of the measured d.c. voltage and the measured d.c. current. electrical power system; electrical power network; power network; power system; electricity supply system (in a broad sense) Particular installations, substations, lines or cables for the transmission and distribution of electricity. [601-01-02] electricity dispenser (ED) An electricity meter device that can (by means such as tokens, cards, keypads) be programmed to allow the flow of a prepurchased amount of energy through an electric circuit.

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electricity dispenser (ED) key register A physically secure environment for the non-volatile storage of the electricity dispenser's current dispenser key. electricity sales system (ESS) A system that consists of combinations of management information systems/management control systems, system master stations, credit dispensing units and electricity dispensers operated by a distributor or by a number of distributors, for the sale of electricity. NOTE In SABS 1524-0, the term "electricity dispensing systems" is used synonymously with the term "electricity sales systems". electric line An arrangement of conductors, insulating materials and accessories for transferring electricity between two points of a system. [601-03-03] electromagnetic compatibility The ability of a device to operate without malfunction in the presence of external electromagnetic interference, as well as the limitation of electromagnetic interference produced by the device itself that could cause malfunction of adjacent equipment such as radios. electromechanical regulator A regulator that uses electromechanical switching devices to control the flow of charge to a battery. NOTE The rate of switching frequency is usually low. electrostatic discharge (ESD) A transfer of electrostatic charge between bodies of different electrostatic potential, in proximity or through direct contact. [IEC Dictionary] encipherment The cryptographic transformation of plaintext data (see cryptography) to produce ciphertext data enclosure A weatherproof housing that is custom-made, or a standard ISO container encryption The cryptographic transformation of plaintext data (see cryptography) to produce ciphertext data. end cap (of an insulated conductor) A cap that is used to seal the end of an insulated conductor against the ingress of moisture and that is held in position by elastic forces only energy absorption capacity The maximum amount of energy (expressed in kilojoules per kilovolt of rated voltage) that an arrester can absorb without its thermal stability being adversely affected equipotential platform An environment where all metallic structures in the vicinity of electronic equipment (for example, cabinets and cable trays) are bonded together, in order to render more benign the electromagnetic environment within which the electronic equipment operates NOTE 1 The process of creating an equipotential platform is known as equipotentialization. NOTE 2 An equipotential platform is typically, but not necessarily, connected to earth. equivalent area The cross-sectional area of a conductive material required to provide the same conductive properties as the conductor used as a reference NOTE This term is used to accommodate the possible use of different materials in, for example, phase and neutral conductors. equivalent span A fictitious single span in which tension variations due to load or temperature changes are nearly the same as in the actual spans in a section of overhead cable

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even harmonics See voltage harmonics. events; occurrences (in the context of the operatio n of sectionalizers) Events that are detectable by the sectionalizer control and that represent the fault conditions against which the power line is to be protected exclusive-or addition; modulo-2 addition A binary addition with no carry, giving the following values: 0+0=0; 0+1=1; 1 +0= 1; 1+1=0. experienced persons persons who by training and demonstration are familiar with the skills and techniques for: (1) distinguishing exposed live parts from other parts of electric equipment; (2) determining the nominal voltage of exposed live parts; and (3) maintaining minimum clearance distances corresponding to the voltages to which that person will be exposed explosion vent A normally closed opening, preferably arranged at the rear or bottom of the metallic enclosure, which, in the case of an internal electrical fault, will rupture or open to release overpressure in a controlled manner to the atmosphere. expulsion fuse A fuse in which operation is accomplished by the expulsion of gases produced by the arc. [IEC Dictionary] external lightning protection system (external LPS) a group of measures that are applied to the outside of a structure, and that involve so-called lightning conductors (air terminations), earthing conductors (down conductors) and earth points (earth terminations), in order to limit the damaging effects of lightning to the structure and to provide a pre-determined path for lightning discharge external supply A term that generally refers to the bulk electricity supply to a township. extra high voltage (EHV) The set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range 220 kV < Un ≤ 400 kV. extruded insulation Insulation that consists generally of one layer of a thermoplastic or thermo-setting material and that is applied by an extrusion process. factor of safety (of any component) The ratio of a component's failing load to the maximum working load for which it is designed. failing load The load at which a deflection begins to show a disproportionate increase in relation to an increase in load. fast curve protection function A family of near-inverse curves with approximately equal operating (delay) times relative to a multiple of the pick-up setting. fault An unplanned occurrence or defect in an item which can result in one or more failures of the item itself or of other associated equipment fault current A current that results from an insulation failure or from the bridging of insulation feeder An electric line originating at a main substation and supplying one or more secondary substations. [601-02-08]

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feeder bay In a substation, the bay relating to a feeder or a link to a transformer, a generator or another substation. [605-02-10] feeder circuit-breaker In a substation, a circuit-breaker which is located within a feeder bay and through which a feeder can be energized. [605-02-38] feeder disconnector A disconnector which is located in series at the end of a feeder, within a substation bay, in order to isolate the feeder from the system. [605-02-44] ferrule; through connector A connector for connecting two consecutive lengths of conductor. fill factor a way of summarizing the differences in the shapes of photovoltaic module current-voltage curves. It is defined as:

scoc

maxmax

IV

IV

××

where Vmax is the module voltage at maximum power Imax is the module current at maximum power Voc is the module voltage on open circuit Isc is the module current on short-circuit All quantities at standard test conditions.

NOTE The fill factor is sometimes used as an indicator of the quality of the photovoltaic cells and modules. In high quality modules, the fill factor is higher. The typical fill factor of a high quality module should exceed 75 %. filler The material used to fill the interstices between the cores of a multiconductor cable. final tripping; lock-out See KS 1859-1 fixed wiring Wiring that is permanently installed to various outlet points. flange The mounting plate that connects the enclosure to the equipment flashover A disruptive discharge over a solid surface float charge voltage The voltage at which a battery is maintained in a fully charged condition without excessive gassing footing resistance The resistance of a structure to earth forced interruption An interruption that

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a) occurs when a component is taken out of service immediately, either automatically or as soon as switching operations can be performed, as a direct result of emergency conditions, or

b) is caused by human error or by the improper operation of equipment formed tie A custom-designed wire strand, or set of wire strands or plastics strands, that has been factory formed to suit a particular insulator neck size, or conductor or stay wire type (or both) frequency (of the power system) See power frequency functionality A defined capability to perform certain functions fully insulated enclosure An unfilled enclosure where those parts of the bushings inside the enclosure, including all live metal parts and cable cores, are fully insulated for the appropriate insulation level fuse-carrier The movable part of a fuse-link assembly designed to carry a fuse-link. [IEC Dictionary] fuse element The part of the fuse-link that is designed to melt under the action of a current that exceeds some definite value for a definite period of time. [IEC Dictionary] fuse link The part of a fuse (including the fuse-element) intended to be replaced after the fuse has operated. fuse-switch A switch in which a fuse-link or a fuse-carrier with fuse-link forms the moving contact. [IEC 441-14-17] gapless arrester An arrester that has no integrated series or parallel spark gaps. gapless metal-oxide surge arrester An arrester having non-linear-metal-oxide resistors connected in series and/or in parallel without any integrated series or parallel spark gaps. [IEC 60099-4] gas-insulated switchgear (GIS) Switchgear which is totally enclosed and whose conductors and busbars are insulated by an inert gas such as sulfur hexafluoride (SF6) general purpose switch A switch capable of performing, with currents upto its rated breaking currents, all making and breaking operations which may normally occur in distribution systems as well as carrying and making short-circuit currents ground span The horizontal distance between supporting structures that, on level ground with the conductor at maximum sag, enables the statutory clearance of the conductor above the ground to be achieved NOTE The ground span is dependent on the structure height, the type of conductor, the temperature, and the tension limits within which the conductor is designed to operate. guy grip dead-end fitting A preformed fitting for attaching a stay wire or rope to other stay components such as anchor rods, thimbles and stay insulators harmonics Sinusoidal components of the fundamental current or voltage waveform (i.e. 50 Hz) that have frequencies that are integral multiples of the fundamental frequency, (see also voltage harmonics)

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high current impulse of an arrester The peak value of discharge current having a 4/10µs impulse shape which is used to test the stability of the arrester on direct lightning strokes highest voltage for equipment ( Um) The highest r.m.s. phase-to-phase voltage for which the equipment is designed in respect of its insulation as well as other characteristics which relate to this voltage in the relevant equipment standards highest (lowest) voltage of a system The highest (lowest) value of operating voltage which occurs under normal operating conditions at any time and any point in the system. [601-01-23/24] NOTE Transient overvoltages caused, for example, by switching operations and abnormal temporary variations of voltage, are not taken into account. high voltage (HV) The set of nominal voltage levels that are used in power systems for bulk transmission of electricity in the range 44 kV < Un < 220 kV high-voltage yard (HV yard) An enclosure that contains exposed overhead medium voltage, high voltage; extra-high voltage or ultra-high voltage components. impedance earthed (neutral) system A system whose neutral points) is (are) earthed through impedances to limit earth fault currents. [601-02-26] independent manual operation A stored-energy operation where the energy originates from manual power, stored and released in one continuous operation such that the speed and force are independent of the action of the operator independent test facility An organization that is not connected to, or part of, the supplier and that is accredited, to the satisfaction of the purchaser, to carry out the required tests indoor substation A substation sheltered from external weather conditions by being installed within a building. [605-02-15] input-output voltage dependency The percentage change in output voltage when the input voltage is varied over a specified range installing authority An authority that initially erects and owns a structure. instrument transformer A transformer specially designed to maintain a certain relationship in phase and magnitude between the primary and secondary voltages or currents. insulated Covered with insulating material of such thickness and properties that the material will prevent the flow of electrical energy between the object so covered and its surroundings or any external object in contact with it. insulated cable An assembly that consists of a) one or more cores, b) the individual covering(s) (if any) of the core(s), and c) the assembly protection (if any). NOTE Additional uninsulated conductor® can be included in the cable.

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insulation (of a cable) Insulating materials incorporated in a cable, with the specific function of withstanding voltage. insulation co-ordination The selection of the dielectric strength of equipment in relation to the voltages which can appear on the system for which the equipment is intended and taking into account the service environment and the characteristics of the available protective devices. insulation level A combination of the relevant of the following:

a) the rated short duration power-frequency withstand voltage;

b) the rated lightning impulse withstand voltage; and

c) the rated switching impulse withstand voltage. insulation piercing connector (IPC) An insulated device that is used for connecting two or more insulated conductors by piercing the insulation of the conductors insulator A device intended for electrical insulation and mechanical fixing of equipment or conductors which are subject to potential differences insulator-fixing stem A component for attaching an insulator to a mounting bracket interharmonics See voltage harmonics. interoperability The ability to exchange keys, whether manually or automatically, between equipment supplied by one manufacturer and operated by one party and equipment supplied by another manufacturer and operated by another party internal lightning protection system (internal LPS) A group of measures that are applied to the volume inside a building, to render the electromagnetic environment more benign.

NOTE This usually involves the creation of equipotential platforms and lightning protection zones. internal network A term that generally refers to all electrical distribution equipment within the boundary of a township up to an agreed interface with the external supply.

NOTE See annex A of KS 1878-1. interruption A phenomenon that occurs when one or more phases of a supply to a customer/group of customers is/are disconnected for a period exceeding 3 s. inverse definite minimum time relay (IDMT relay) A relay the minimum operating time of which is adjustable and is inversely proportional to the fault current. inverter A device which changes d.c. input into a.c. output. [IEC 61277] isolation voltage The maximum a.c. or d.c. voltage that may be continuously applied between the input and either the output or the chassis of equipment. joggle chamber A purpose designed panel used to align the busbars of different types of metal-clad switchgear.

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joint A connection between two conductors, sheaths or armour wires, including their insulation, if any, to form a continuous circuit. key activation date An attribute associated with a vending key value that defines the date upon which the vending key becomes the supply group's current vending key, and the date upon which the associated key revision number becomes the supply group's key revision number key block In the context of the standard on data encryption (ANSI X3.92), the 64 bit block of data that contains the 56 bit key key expiry number An attribute associated with a key value that defines the period during which the key value can be used

NOTE 1 A token that is encrypted with a key whose token identifier exceeds the electricity dispenser's key expiry number for the key will be rejected by the electricity dispenser.

NOTE 2 Implementation of key expiry is optional for an electricity dispenser. key revision number An attribute associated with a key value and that provides a key sequencing identifier key type An attribute associated with a key value and that defines the purpose for which the key value can be used kiosk substation See KS 1859-1. kneepoint voltage The r.m.s. value of sinusoidal voltage at rated frequency applied to the secondary terminals of the transformer, all other windings being open-circuited, which, when increased by 10 %, causes the r.m.s. value of the excitation current to increase by 50 % lapped separator (of a cable) A separator that consists of tapes applied helically in a concentric layer large customer Any large power user with a notified maximum demand that exceeds 100 kVA lashed cable A telecommunication cable, of circular cross-section, that is attached to a suspender wire on an overhead line, by means of a lashing wire wrapped around the cable and suspender wire lashing wire Thin galvanized or stainless steel wire that is used to attach a telecommunication cable to a suspender wire lead wires (of a photoelectric control unit (PECU)) Three separate wires that lead from a one-part PECU and that are intended for direct connection to the power supply and the load length of lay (of a cable) The axial length of one complete turn of the helix formed by one cable component licensee A supply authority licensed by the NER to distribute electricity lightning impulse An impulse voltage, applied during dielectric tests complying with standards, with a front duration of the order of 1 ms and a time to half value of the order of 50 ms. NOTE The lightning impulse is defined by the two figures that give these durations in microseconds; in particular the standard lightning impulse is 1.2/50 µs.

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lightning (or switching) impulse protective level The maximum permissible peak voltage value on the terminals of a protective device subjected to lightning (or switching) impulses under specific conditions lightning impulse withstand voltage The lightning impulse voltage that an insulator under prescribed conditions of test will withstand when the insulator is dry. lightning (or switching) impulse protective level The maximum permissible peak voltage value on the terminals of a protective device subjected to lightning (or switching) impulses under specific conditions lightning protection zone (LPZ) A volume in which the lightning electromagnetic environment, in terms of conducted surges and radiated fields, is defined, quantified and managed. The boundaries between zones are established by suitable screening and bonding measures and by surge protection devices NOTE The following lightning protection zones are characterized by significant changes of the electromagnetic conditions at their boundaries:

a) LPZ 0A: possible direct lightning strikes, and unattenuated electromagnetic fields, for example a zone with exposed

conductors outside a structure; b) LPZ ob: no direct lightning strikes, but unattenuated electromagnetic fields can occur, for example a zone with buried

conductors or screened cables outside a structure; c) LPZ 1: no direct lightning strikes, but currents on conductive parts and electromagnetic fields are attenuated with respect to

LPZ 0A and LPX ob, for example a zone inside a structure; and d) LPZ 2: no direct lightning strikes, but currents in conductive parts and electromagnetic fields are attenuated with respect to

LPZ 1, for example a protected zone inside a structure, such as a computer room. limit range of operation Extreme conditions that an operating instrument can withstand damage to and without degradation of its metrological characteristics when it is subsequently operated under its rated operating conditions limited purpose switch A switch which complies only with one or more but not with all service applications of a general purpose switch line An arrangement of conductors, insulating materials and accessories, supported above ground level by structures, for transferring electricity between two points of a system line voltage drop The difference, at a given instant, between the magnitudes of the r.m.s. voltages measured at two given points along a line. link See KS 1859-1. live Electrically charged, or capable of being electrically charged at any time load A device that absorbs power load curve See KS 1859-1. load duration curve See KS 1859-1. load factor A factor to allow for the average period in which an appliance uses the maximum load.

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load sensing A preferred characteristic of an inverter such that if no load is connected to the output of the inverter the inverter automatically switches to a standby mode and the input current is minimized NOTE This avoids unnecessary discharge of the storage battery. The inverter should automatically revert to normal operation when a load is reconnected. load-shed voltage The voltage at which the regulator is set to disconnect loads to protect the battery from further discharge to prevent premature damage to the battery due to repeated cycles at low states of charge NOTE This set-point is set to the voltage when the maximum permitted depth of discharge is reached. load shedding The process of deliberately disconnecting preselected loads from a power system in response to an abnormal condition, in order to maintain the integrity of the remainder of the system load reconnect voltage The voltage set-point of the regulator at which the loads are reconnected to the battery after load-shed has occurred load transfer See KS 1859-1. lock-out See KS 1859-1. lost call A telephone call that gets through to the licensee but that is not answered lower contact The load-side contact of a cut-out base, which also allows a removable fuse-carrier or solid-link to pivot low voltage (LV) See KS 1859-1. lug A connector that comprises a palm and a connector barrel, for connecting a conductor to an equipment terminal luminaire An apparatus that distributes, filters, or otherwise transforms the light from one or more lamps (or fulfils more than one of these functions), and that includes all the parts necessary for supporting, fixing and protecting the lamp(s), (but excludes the lamps themselves), as well as circuit auxiliaries, such as ballasts and capacitors, together with the means for connecting them to the supply NOTE Where "luminaire" is used in this part of KS 1878 and it is evident that a lamp or lamps are necessary to give meaning to the use of the word, the term should be taken to include the lamp(s). magnetic card electricity dispenser An electricity dispenser that incorporates magnetic card token technology as the mechanism for inputting standard transfer specification tokens magnetic card token technology A technology that enables entry, by a human, of a standard transfer specification disposable magnetic card token into a device via a magnetic card reader main circuit All the conductive parts of an assembly of switchgear and controlgear included in a circuit that is intended to transmit electrical energy maintenance history A detailed log of all the service details pertaining to an item of plant

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manufacturer's identification marks Markings that include the manufacturer's name or trademark and the fitting reference mass span Those portions of the span lengths on either side of the structure that impose a vertical load on the structure NOTE The maximum mass span that can be supported by the structure is dependent on the strength of the structure and the strength of the supporting hardware, including insulators. The mass span is calculated using the mass per unit length of the conductor supported by the structure. maximum continuous operating voltage (MCOV or Uc) The highest r.m.s. power-frequency voltage that an arrester can withstand continuously. maximum demand The highest registered electrical demand integrated for a specified period. maximum demand indicator (MDI) An instrument that has a resettable pointer to indicate the maximum demand of the equipment during a specified period. maximum permitted depth of discharge (DOD) The maximum permitted charge depletion chosen to prevent premature damage to the battery. NOTE The maximum permitted DOD is indicated approximately by the battery voltage. A suitable settling time has to be allowed for under open-circuit conditions. medium voltage (MV) See KS 1859-1. mesh (of a system) See KS 1859-1 meshed system See KS 1859-1. mesh substation See KS 1859-1. metal-clad switchgear Metal-enclosed switchgear in which certain components (e.g. circuit-breakers) are arranged in separate compartments that have metal partitions and are intended to be earthed. NOTE This term applies to metal-enclosed switchgear with metal partitions that provide the degree of protection, or a higher degree, included in table 1 of EC 60298:1981, Amendment No. 1:1987, and that has separate compartments for the following:

a) each main switching device; b) components connected to one side of a main switching device (e.g. a feeder); and c) components connected to the other side of the main switching device (e.g. busbars).

metal-enclosed switchgear and controlgear See switchgear and controlgear - metal-enclosed. metal-oxide varistor (MOV) A highly non-linear varistor that has a high impedance at power-frequency voltage and a very low impedance to overvoltages that exceed the MCOV. metal-sheathed cable A cable provided with a metal sheath for the purpose of excluding moisture from the conductors and their insulation. miniature circuit-breaker (MCB) A circuit-breaker that is usually designed to clip onto a standard mounting rail on a distribution board

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mini-substation (mini-sub) A factory-assembled and tested free-standing unit that is suitable for use in an area accessible to the public, that comprises a transformer, an equipped medium-voltage compartment and an equipped low-voltage compartment and that is suitable for connection to underground cables module The smallest complete environmentally protected assembly of interconnected solar cells modulo-2 addition A binary addition with no carry, giving the following values 0 + 0 = 0; 0 + 1=1; 1 +0 = 1; 1+1=0. moulded-case circuit-breaker (MCCB) A circuit-breaker that has a supporting housing of moulded insulating material forming an integral part of the circuit-breaker mounting L-bracket (of an outdoor distribution cut- out) A device used to facilitate the mounting of a cut-out on either a wooden cross-arm or a steel cross-arm. multipair cable A cable that consists of a number of pairs of insulated conductors. multiple-point earthing Earthing of the protective conductor at points on the distributor in addition to the source earthing of the medium-voltage/low-voltage transformer neutral point. mutual induction The electromagnetic induction in an electrical circuit arising from the current flowing in another circuit. MV equipment earth A continuous earth that has the combined effect of bonding metal tanks of transformers, switchgear, surge arresters and all metalwork supporting or enclosing medium-voltage apparatus, including the sheaths and armouring of medium-voltage cables and any continuous earth conductors associated with the medium-voltage system, to an earth electrode, direct. neutral See KS 1859-1. neutral point in a polyphase system See KS 1859-1. nominal discharge current The peak value of lightning current impulse which is used to classify an arrester. [IEC 60099-4] nominal power The designated power of a device, expressed either in watts (W) or in volt-amperes (VA) and reflected on a nameplate. nominal voltage of a system A suitable approximate value of voltage used to designate or identify a system. [IEV 601-01-21] non-directional protection Protection that operates when a fault occurs on either side of a given reference point. normal operating (PV) cell temperature The temperature of a photovoltaic cell when subjected to an irradiance of 800 W/m2, an ambient temperature 20 °C, and a wind velocity of 1m/s. non-load-breaking connector A bushing and its associated premoulded elbow connector, which cannot be removed safely while a load is being carried.

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number of cells in a battery The number of series-connected cells which make up the complete battery. occurrences See events. odd harmonics See voltage harmonics. off-load switching device See KS 1859-1. one-way function A function y = f(x) that is relatively easy to compute, but the inverse of which is much more difficult to compute (in other words, given x, it is easy to find y, but given a value y it is difficult to find any solution x of y = f(x)) on-load switching device See KS 1859-1. opening; tripping See KS 1859-1. open-type substation See KS 1859-1. operating voltage (in a system) See KS 1859-1. origin integrity The corroboration that the source of data received is as claimed. outdoor distribution cut-out A drop-out vented expulsion fuse-link assembly or solid-link assembly, together with the associated components. outdoor substation See KS 1859-1. overcurrent A current of a value exceeding the highest rated value. [IEC Dictionary] overhead earth wire See KS 1859-1. overhead line See KS 1859-1. (See also power line.) overhead system See KS 1859-1. oversheath (of a cable) A non-metallic sheath that is applied over a metallic covering, such as armouring, and that constitutes the outermost sheath of the cable. overturn span (of an overhead line) The maximum span length capability of the structure foundation under maximum wind load conditions with the statutory foundation factor of safety (currently 2). overvoltage Any voltage, between one phase and earth or between phase conductors, that has a peak value exceeding the corresponding peak value (Um√2/√3 or Um√2 respectively) of the highest voltage for equipment.

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pair Two insulated conductors twisted together. panel A group of modules fastened together, pre-assembled and wired, designed to serve as an installable unit in an array and/or sub-array. [IEC 61277] parallel groove (PG) clamp A bolted connector that has parallel grooves and that accommodates two conductors that could be of similar or of different sizes and materials. parent key A key used to encrypt a child key for the purpose of concealing the child key, in order to prevent its undetected modification or unauthorized use (or both). partially insulated enclosure An unfilled enclosure in which the cable cores only are fully insulated for the appropriate insulation level. (NRS 008) PCB free containing 2 ppm (or less) polychlorinated biphenyls (PCB). peak load See KS 1859-1. PE conductor A protective (earth) conductor that is separate from the neutral conductor. PEN conductor A conductor that functions as both a protective conductor and a neutral conductor.

percentage depth of discharge The amount of charge removed from a fully charged battery at a specified discharge rate, expressed as a percentage of the battery's rated capacity.

NOTE 1 The removal of 25 Ah at the specified discharge rate applicable to the rating of the battery from a fully charged 100 Ah rated battery results in a 25 % depth of discharge

NOTE 2 One hundred per cent DOD means fully discharged; zero percent DOD means fully charged.

permanent fault See KS 1859-1.

phase See KS 1859-1.

phase-to-earth voltage See KS 1859-1.

phase-to-neutral voltage See KS 1859-1. phase-to-phase voltage See KS 1859-1.

photoelectric control unit (PECU) A device that comprises a photoelectric sensor that responds to variations in illuminance and that is combined with a means of switching an electric load.

physically secure environment An environment in the form of a facility, enclosure or device the penetration of which, in any manner, actively renders unintelligible any secret data contained therein, or that itself precludes any penetration that could allow disclosure of secret data. pick-up setting An expression which is a variable used to indicate sensitivity activation level of a protection device. pin connector

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A connector that has a solid cylindrical stub at one end and a connector barrel at the other end. planned interruption An interruption that occurs when a component is deliberately taken out of service (by the utility or its agent) at a selected time, usually for the purposes of construction, preventative maintenance or repair. point of common coupling (PCC) The point in a network where more than one customer is connected or will be connected. point of control The point at which the electrical installation on or in any premises can be switched off by a user or lessor from the electricity supplied from the point of supply. point of metering See KS 1859-1. point of supply The point at which electricity is supplied to any premises by a supplier. pole-mounted remote terminal unit (PMRTU) A remote terminal unit that is designed for pole mounting and that operates specific pole-mounted equipment remotely. pole-mounted substation See KS 1859-1. pole pike A device that is used to assist the manual erection of poles. The top end usually consists of an aluminium tube of diameter approximately 75 mm, with the lower end being flat with a pair of handles. NOTE For the erection of wooden poles, a single pike or a pair of pikes secures the pole during erection and backfill operations. pole-top make-off A preformed fitting designed to secure a component to the top of a pole. post insulator (in junction boxes) A structure that supports one or more conductors, and that insulates it or them from the point on the enclosure to which the structure is attached, including the means of attachment. (MRS 008) power factor The ratio of the total power (in watts) dissipated in an electric circuit to the total equivalent volt-amperes applied to that circuit. power frequency; frequency The frequency of alternating voltage generated by power system generators. (See also KS 1859-1.) power line An overhead line that is erected to convey electrical energy for any purpose other than communication, but that excludes the overhead contact or catenary wires of an electric traction system. (See also overhead line.) power rating The designed power output of an item of equipment as stated on its rating plate under the specified conditions, measured in kilowatts (kW). preferred The most desirable from a selection of options, unless otherwise specified. prescription Limitation by law of the time within which a claim can be made. pressure relief device of an arrester Means for relieving internal pressure in an arrester and preventing violent shattering of the housing following prolonged passage of fault current or internal flashover of the arrester.

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pressure relief rated current The continuous current through the arrester that will cause the pressure relief device to operate, thus relieving the internal pressure inside the arrester and preventing violent shattering of the housing. probability distribution function (PDF) (of a sampl ed load) A function that describes the probability that a certain value might appear as the sampled load. NOTE This function is derived from the cumulative distribution function. protection The provision for detecting abnormal conditions in a power system and then initiating signals, indications or clearance of the condition, or a combination of these. protection capability The ability to perform the functions of a protection relay or protection device. protection device A device designated to perform a specific protection function. protective conductor A conductor that forms part of a low-voltage distributor, and that connects the source earth to the consumer's earth terminal. The conductor is also connected to other earth electrodes and exposed conductive parts of the low-voltage distributor. protective level of a protective device (PL orUpl) The highest peak voltage value that should not be exceeded at the terminals of a protective device when switching impulses and lightning impulses of standard shapes and rated values are applied under specified conditions. p.u. voltage (phase to earth) A theoretical unit of voltage equal to the peak value of the maximum system voltage with reference to earth. NOTE 1 p.U. = Um√2/√3 kV. puncture A disruptive discharge through a solid. [IEC 60099-4] quality of supply (QOS) Technical parameters to describe the electricity supplied to customers, and that are used to determine the extent to which the needs of customers are met in the utilization of electricity. radial feeder See single feeder. radial system See KS 1859-1. rapid protection operation A protection function that enables rapid breaker operation, be it an instantaneous protection function (i.e. operation with no intentional time delay), a fast curve protection function, or an instantaneous protection function with a relatively short definite time delay. rated capacity of a cell or battery The quantity of electricity, declared by the manufacturer, which a cell or battery can deliver under specified conditions. NOTE 1 Typically at a constant discharge current and battery temperature after a full charge. For a current I20 which will fully discharge the battery in 20 h, the rated capacity is abbreviated to C20. NOTE 2 This value is usually expressed in ampere-hours. [IEV 486-03-22] rated discharge current the peak value of lightning current impulse which is used to classify an arrester [IEC 60099-4]

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rated frequency The frequency at which the equipment is designed to operate. rated impulse withstand voltage The prescribed peak value of the (switching/lightning) impulse withstand voltage which characterizes the insulation of an equipment as regards the withstand tests. [IEC 60071-1] rated insulation level (a) A set of standard withstand voltages which characterize the dielectric strength of the insulation [IEC 60071-1] rated insulation level (b) The combination of the rated lightning impulse withstand voltage and the rated short duration power frequency withstand voltage specified in Table 2 of IEC 60298. rated kneepoint voltage The kneepoint voltage on which the performance of class X current transformers is based and which is marked on the rating plate. rated normal current For main circuits and switching devices, the r.m.s. value of current that they shall be able to carry continuously under the specified conditions of use and behaviour. rated peak withstand current For main and earthing circuits, the peak current associated with the first major loop of the short-time withstand current that a mechanical switching device shall be able to carry in the closed position under prescribed conditions of use and behaviour. rated short-circuit breaking current Of a switch-fuse combination, the highest prospective short-circuit current that the combination shall be capable of breaking under the conditions of use and behaviour defined, and expressed by the r.m.s. value of its a.c. component. rated short-time withstand current For main and earthing circuits, the r.m.s. value of current that the switching device shall be able to carry in the closed position during a specified short time under prescribed conditions of use and behaviour. rated voltage The highest r.m.s. phase-to-phase voltage of the supply for which the equipment is designed. rated voltage of an arrester The maximum permissible r.m.s. value of power-frequency voltage between an arrester's terminals at which it is designed to operate correctly under temporary overvoltage conditions as established in the operating duty tests. The rated voltage is used as a reference parameter for the specification of operating characteristics. NOTE The rated voltage as defined in this guide is the 10s power-frequency voltage that is used in the operating duty test after high-current impulses or long-duration impulses. Tests used to establish the voltage rating in IEC 60099-1, and also in some National Standards, involve the application of repetitive impulses at nominal current with power-frequency voltage applied. Attention is drawn to the fact that these two methods that are used to establish rating do not necessarily produce equivalent values. (The resolution of this discrepancy is under consideration.) real power of a power inverter The power measured at the output side of the inverter using a wattmeter of suitable bandwidth. reference current of an arrester The peak value (the higher peak value of the two polarities if the current is asymmetrical) of the resistive component of a power-frequency current that is used to determine the reference voltage of the arrester. NOTE Depending on the nominal discharge current or the line discharge class (or both) of the arrester, the reference current will be typically in the range 0.05 mA to 1.0 mA per square centimetre of disc area for single column arresters. reference voltage of an arrester ( Uref)

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The peak value of power-frequency voltage divided by √2, that is applied to an arrester to obtain the reference current. The reference voltage of a multi-unit arrester is the sum of the reference voltages of the individual units. NOTE Measurement of the reference voltage is necessary for the selection of a correct lest sample in the operating duty test. [IEC 60099-4] reinforcement of a system See KS 1859-1. relative density The ratio of the density of a substance to the density of a standard, usually water in the case of a liquid or solid, and air in the case of a gas. relay chamber A metal-enclosed chamber that contains control, measuring, indicating, alarm, protective and regulating equipment associated with a switchgear panel. remote station A station which is monitored, or commanded and monitored by a master station. [IEV 371-06-04] [IEC 60970-1-3] residual voltage (discharge voltage) The voltage that is maintained between the arrester terminals during the passage of discharge current, and that determines the protective characteristics of the arrester. residual voltage winding The winding of a transformer between the terminals of which is produced the residual voltage or one of the three component voltages which, when added together, constitute the residual voltage. [IEC Dictionary] restraint (in the context of sectionalizer operatio n) protection parameter limits that prevent sectionalizer operation, for example current inrush and low-current restraint restricted earth fault relay An earth fault relay that is unconditionally stable for faults outside the protected zone but that will operate for earth faults above the preset value within the zone. ring feeder See KS 1859-1. ring main An electrical supply through cable in a closed ring providing alternative paths. ring main switch A switch housed in a ring main unit and connected in a ring main. ring main unit A switchgear assembly that has an external metal enclosure and that comprises switch disconnectors, switch-fuse combinations or circuit-breakers. These would incorporate integral cable earthing and can have facilities for cable test. routine test A test that is required to be carried out on every item or batch of items before delivery. Rural Descriptive of an area that has clustered or scattered structures, usually of low density, and that is not served by a well-established infrastructure (roads, telecommunication, etc.). NOTE Electricity is usually supplied radially by overhead lines emanating from one distribution station. rural (networks or system)

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Networks or systems serving clustered or scattered structures, usually of low density, not served by well established infrastructure (roads, telecommunications, etc.). The power network is usually supplied radially by overhead lines emanating from one distribution station. sag The maximum vertical distance between a conductor that spans between supports, and a straight line that joins the conductor's points of support. sample test A test carried out on a sample (of a completed product) or on components threof so as to verify that the finished product complies with the design specifications. screen (of a cable) Conducting layer(s) having the function of control of the electric field within the insulation. NOTE A screen may also provide smooth surfaces at the boundaries of the insulation and assist in the elimination of spaces at these boundaries. sealed end (of a cable) A termination to the end of the cable, which provides a seal from the external environment and maintains the filling within the cable. secure control (in the context of auto-recloser ope ration) A single non-latching switch that affects one control only. seed key A key used by an algorithm as a starting or initializing value for the generation of another value. self-monitoring (fault) A condition whereby a fault, that does not cause the system protection to operate, will manifest itself in another way, usually by failure of the consumer's apparatus to operate. self-restoring insulation Insulation which completely recovers its insulating properties after a disruptive discharge. [IEV 604-03-04] self-supporting ABC A multicore ABC system in which all cores are under tension. sensitive earth fault (SEF) relay A relay that is sensitive to very low earth fault currents and in which the operating settings are for current magnitude with a definite time delay. sensitive earth fault (SEF) sensing An arrangement that renders the sectionalizer sensitive to very low earth fault currents. separate neutral and earth (SNE) cable A cable or distributor in which the neutral conductor and the earth conductor are electrically separated from each other. separation distance The minimum distance between power conductors and telecommunication conductors. separator A thin layer used as a barrier to prevent mutually detrimental effects between different components of a cable, such as between the conductor and the insulation or between the insulation and the sheath. series regulator A regulator that prevents overcharging of a battery by disconnecting the photovoltaic current in an array and effectively placing the array in open circuit. NOTE The switching frequency can be high, thus having small voltage sags. service conductor A branch line from the electrical distribution system, to supply one or more customers.

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service connection A tapping from a distributor, usually of a smaller cross-sectional area, to supply one or more consumers. service distribution box A prefabricated box, with or without protective devices, for terminating several service connections to the distribution line(s). service distribution point (SDP) A generic term for LV distribution boxes, cluster metering boxes, LV kiosks, pillars, pole-boxes, etc., used for supplying consumers from a distributor. service position The position of a removable part in which it is fully connected for its intended function. sheath A uniform and continuous tubular covering of metallic or non-metallic material, generally extruded. shield (of a cable) A surrounding earthed metallic layer to confine the electric field within the cable or to protect the cable from external electrical influence (or both). shielding; screening A conductive covering that surrounds conductors or equipment and that is primarily intended to prevent externally generated interference from impinging on the conductors or equipment. short-circuit The accidental or intentional connection by a relatively low impedance of two or more points on a circuit which are normally at different potentials. [IEC Dictionary] short-circuit protection A protective feature that limits the current under short-circuit conditions, to prevent the equipment from being damaged. shunt regulator A regulator that prevents overcharging of a battery by shunting the photovoltaic array current to a low-impedance bypass. single earthing switch A three-phase switch on one side of a disconnector. single feeder; radial feeder See KS 1859-1. single-point (source) earthing The earthing of the distributor neutral conductor at the medium-voltage/low-voltage transformer neutral point

single supply See KS 1859-1. skid boards Panels that have a smooth clean upper surface that is placed between the butt of the pole and the face of the excavation, to facilitate the erection of the pole. slenderness factor ( S) A ratio that characterizes the shape of a specific probability distribution curve (= mean/standard deviation).

small power distribution unit A ready-wired distribution box or board with appropriate circuit-breaker protection and socket-outlets, which is suitable for direct connection to a customer's electricity dispenser or meter.

solid conductor A conductor that consists of a single wire.

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solid-link A component for use in place of a fuse-carrier, to effect a manual disconnection. solid-link assembly An assembly that comprises all components that form a complete device intended to isolate equipment or parts of a reticulation system, or both, form the source of supply. solid-state regulator A regulator that uses solid-state switching devices to control the flow of charge to a battery. NOTE The rate of switching is typically at high frequency. solidly earthed neutral system A system whose neutral point(s) is(are) earthed directly. [IEV 601-02-25] split-concentric cable A sheathed cable that has a phase core surrounded by two conductors, a neutral conductor and an earth conductor, that, together, form a single concentric layer around the phase core, the two conductors being separated from each other by insulating material. spur feeder See branch line. standard specification A Kenya specification issued in terms of the Standards Act, Cap 496, provided that, until such time as a Kenya specification has been issued, the latest revision of another appropriate national specification or an appropriate International Electro-technical Commission specification shall be deemed to be the standard specification. standard test conditions (STC) Conditions where the irradiance is 1 000 W/m2, the temperature of the photovoltaic cell is 25 °C and the air mass is 1,5 (see 3.1.1). (NRS 052-1:1999) standard voltage The phase voltage of 230 V, measured between a phase conductor, and the neutral conductor, or a line voltage of √3 × 230 V, measured between phase conductors. standby current Current drawn by an inverter when no load is connected to the output. NOTE This should be as small as possible to avoid unnecessary discharge of the storage battery. statistical energy (check) metering The metering at the substation, feeder or bulk supply level, of the energy supplied to a project or supply group. stay A steel wire, rope or rod, working under tension, connecting a point of support to a separate anchor, or connecting two points of the support. [IEC Dictionary] stay insulator An insulator designed to withstand the tension of a stay wire or rope and to insulate the lower portion of the stay from leakage currents, but not from fault currents. stored-energy operation An operation by means of energy stored in the mechanism itself prior to the completion of the operation and sufficient to complete it under predetermined conditions. stored energy operation (of a mechanical switching device) An operation that is completed under predetermined conditions by using energy stored in the switching device prior to the completion of the operation. strain fitting

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A fitting that transfers the tensile load between the supporting conductor and the strain resisting structures of an ABC system. stranded conductor a conductor consisting of a number of individual wires, all or some of which generally have a helical form. [IEV 461-91-07] structure (of a building) A building or part of an installation or part of a plant, inside of which a lightning protection zone can be established. structure (of an overhead line) A construction, of wood, concrete or steel, used in a line to support conductors or cables (or both) and associated accessories and equipment above the ground. substation A part of an electrical system confined to a given area, mainly including ends of transmission or distribution lines, electrical switchgear and controlgear, buildings and transformers. [IEC Dictionary] NOTE A substation generally includes safety or control devices (for example, protection devices). Supervisory Remote control and indications of an auto-recloser or a pole-mounted remote terminal unit by means of a telecommunication link. supplier; manufacturer A person or company from whom equipment, materials or services can be obtained. supplier (of electricity) Any authority that, in terms of legislation, has the right to supply electricity. NOTE "Electricity supplier" should always be used instead of "supplier". supply (of electricity) See KS 1859-1. supply authority See utility. NOTE The preferred term is "electricity supplier". supply group key revision number An attribute of a supply group and that defines the current key revision number for the supply group, and therefore the current vending key value for the supply group (see also key revision number). supply voltage See KS 1859-1. supporting conductor ABC A multicore ABC system that is so installed that only the neutral conductor is under tension. surge A transient overvoltage or transient overcurrent. surge isolation device (SID) A component such as an isolation transformer, optocoupler or fibre-optic link, the purpose of which is to protect electronic equipment from surges by means of galvanic isolation. surge management device (SMD) A term that is used to include either a surge isolation device (SID) or a surge protection device (SPD). surge protection device (SPD); transient suppressio n device (TSD)

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A circuit that consists possibly of silicon suppressors, metal oxide varistors (MOVs) and spark gaps (gas gaps), the purpose of which is to limit transient overvoltages and transient overcurrents, appearing on cables, to levels that are safe for the electronic equipment connected to those cables. NOTE There are two basic types of SPD: a) a type I SPD, which is a current diverting device (for example, a spark gap); and b) a type II SPD, which is a voltage clamping device (for example, a metal-oxide varistor (MOV)). suspender wire A steel, multistranded wire that is used to support a telecommunication cable on an overhead line. suspension fitting A fitting that supports a service cable or conductor at intermediate positions between strain fittings. switch A mechanical switching device capable of making, carrying and breaking currents under normal circuit conditions, which may include specified operating overload conditions, and also carrying for a specified time, currents under specified abnormal circuit conditions such as those of short-circuit. NOTE A switch may be capable of making but not breaking short-circuit currents. switchboard A general term that covers switching devices and their associated control, measuring, indicating, alarm, protection and regulating equipment, also assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures, intended in principle for use in connection with the generation, transmission, distribution and conversion of electric energy switch disconnector A mechanical switching device which provides, in the open position, an isolating distance in accordance with specified requirements switch-disconnector panel A switchgear panel complete with a non-withdrawable type switch-disconnector or switch-isolator. switch-fuse A switch in which one or more poles have a fuse in series in a composite unit. switch-fuse combination A switch in which one or more poles have a fuse in series in a composite unit. switch-fuse panel A switchgear panel complete with a non-withdrawable switch-fuse. switchgear A general term covering switching devices and their combination with associated control, measuring, protective and regulating equipment, also assemblies of such devices and equipment with associated interconnections, accessories, enclosures and supporting structures, intended for use in connection with generation, distribution and conversion of electrical energy. switchgear – indoor Switchgear and controlgear designed solely for installation within a building or other housing, where the switchgear and controlgear are protected against wind, rain, snow, abnormal dirt deposits, abnormal condensation, ice and frost. switchgear – outdoor Switchgear and controlgear suitable for installation in the open air, i.e. capable of withstanding wind, rain, snow, dirt deposits, condensation, ice and frost. switchgear and controlgear - metal-enclosed Switchgear and controlgear assemblies with an external metal enclosure intended to be earthed, and complete except for external connections.

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switchgear panel A switchgear panel of modular design that comprises a mechanical switching device (e.g. a circuit-breaker, a switch, a switch-disconnector or a switch-fuse) and its associated control, measuring, indicating, alarm, protection and regulating equipment with interconnections, accessories, enclosures and support structure. switching differential The ratio of the measured switch-on level to the measured switch-off level switching unit of a photoelectric control unit (PEC U) The part of a two-part PECU that contains the load-switching device. symmetrical fault An insulation fault at one point of a circuit, that affects the insulation of all three-phase conductors between one another and usually to earth. [IEC Dictionary] synchronization The matching of two systems with respect to their frequency and to their voltage magnitude and voltage phase for interconnection purposes. [IEC Dictionary] synchronization of two systems See KS 1859-1. System See KS 1859-1 system configuration See KS 1859-1 system demand control See KS 1859-1. system earthing – effective An earthed system, or portion of the system, in which the power frequency phase-to-earth overvoltages associated with earth faults are limited to 0.8Um. system earthing - non-effective A system in which the neutral is intentionally connected to the system earth through a current limiting device. take-over The act of taking over equipment by the purchaser to operate, after it has been accepted and approved, with or without reservations

NOTE The date of take-over is often associated with the commencement of a guarantee period. take-over current The current co-ordinate of the intersection between the time-current characteristics of two overcurrent protective devices tapped (tee off) substation See KS 1859-1. tariff The price structure for electricity supplied to a point of supply tee-connector A premoulded connector for connection to a bushing in conjunction with an elbow connector to permit termination of a second cable core to a bushing teed feeder See KS 1859-1. teed system See KS 1859-1.

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telecommunications authority The authority responsible for administering the Kenya Communications Act templating The activity of placing or positioning the structure on the ground profile, drawing or map temporary overvoltage (TOV) An oscillatory phase-to-earth or phase-to-phase overvoltage at a given location in a system, of relatively long duration and that is undamped or only weakly damped

NOTE Temporary overvoltages usually originate from switching operations or faults (e.g. load rejection, single-phase faults) or from non-linearities (ferro-resonance effects, harmonics). They may be characterized by their amplitude, their oscillation frequencies, and by their total duration or their decrement. temporary supply An electricity supply that is provided to a customer in the event of unusual circumstances. Such a supply might not conform to the service levels normally provided by agreement between the customer and the licensee tensile load The tensile load applied during testing, and at which the cable breaks or becomes permanently deformed terminal assembly Two or more terminals fixed to the same conductive part terminal block An insulating part carrying one or more mutually insulated terminal assemblies and intended to be fixed to a support test position (of a withdrawable part) The position of a withdrawable part in which an isolating distance or segregation is established in the main circuit, and in which the auxiliaries are connected thermal runaway of an arrester The term "thermal runaway" is used to describe a situation when the sustained power loss of an arrester exceeds the thermal dissipation capability of the housing and connections, leading to a cumulative increase in the temperature of the resistor elements culminating in failure thermal stability of an arrester An arrester is thermally stable if, after an operating duty causing temperature rise, the temperature of the resistor elements decreases with time, when the arrester is energized at specific continuous operating voltage and at specified ambient conditions thimble A component designed to protect a stay wire or rope against abrasion and excessive bending at a termination through connector See ferrule. tie clamp The part of a cable tie that binds together its ends round the cables that it ties toggled control A single latching switch that enables a single control operation in one position and disables the same control operation in the other position. token identifier A value associated with a token and that distinguishes the token from other tokens issued for the same electricity dispenser it is derived from the date and time the token is issued at the credit dispenser total harmonic distortion See voltage harmonics.

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touch voltage The voltage that, during a fault, appears between simultaneously accessible conductive parts tracking The progressive formation of conducting paths on the surface of a solid insulating material, and caused by the combined effects of electric stress and electrolytic contamination on this surface. transformer See KS 1859-1. transient fault See KS 1859-1. transient overcurrent A current that flows as a result of a transient overvoltage. transient overvoltage A short duration overvoltage of a few milliseconds or less, oscillatory or non-oscillatory, usually highly damped. [IEV 604-03-13] transient suppression device (TSD) See surge protection device. trip-free facility A facility on a mechanical switching device, such that the contacts close fully, then return to and remain in the open position when the closing operation is initiated after the initiation of the trip operation, even if the closing command is maintained. trip-free mechanical switching device A mechanical switching device, the moving contacts of which return to and remain in the open position when the opening operation is initiated after the initiation of the closing operation, even if the closing command is maintained.

NOTE To ensure proper breaking of the current which may have been established, it may be necessary that the contacts momentarily reach the closed position. tripping See KS 1859-1. twinning The process of twisting two insulated conductors (cores) together to form a pair. type test A test that is required to be carried out on equipment to prove that the equipment complies with certain specifications applicable to its acceptability for the purpose for which it was intended. ultimate tensile strength (UTS) The highest load applied to a metal in the course of a tensile test, divided by the original cross-sectional area. ultra-high voltage (UHV) See KS 1859-1. ultraviolet-stabilized Modified by methods such as carbon loading to withstand ultraviolet radiation. undercut The peripheral portion of an excavation which is undercut to ensure that the stay anchor assembly bears against undisturbed soil underground cable See KS 1859-1 underground system

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See KS 1859-1. unfilled enclosure A metallic enclosure designed for the purpose of receiving and protecting the end(s) of cable(s) in air. NOTE It follows that such an enclosure can be self-contained and removable; it can also be a compartment of the connected equipment and therefore an integral feature of that equipment; it can also be a stand-alone item of equipment, for example a junction box. unique group See unique supply group unique supply group A supply group that associates a set of electricity dispensers on a geographical or a regional basis, in which each and every electricity dispenser in the supply group has a unique dispenser key. unit (of an arrester) A completely housed part of an arrester which can be connected in series and/or in parallel with other units to construct an arrester of higher voltage and/or current rating. [SABS IEC 60099-4] NOTE A unit of an arrester is not necessarily a section of an arrester. unit of an arrester A completely housed part of an arrester which may be connected in series and/or in parallel with other units to construct an arrester of higher voltage and/or current rating. A unit of an arrester is not necessarily a section of an arrester. [IEC 60099-4] unit protection See KS 1859-1. upper contact The source-side spring-loaded contact of a cut-out base. urban Descriptive of an area that has formally or informally built structures, usually of high density, served by a well-established infrastructure (roads, telecommunication networks, etc.). The power network is usually supplied by more than one distribution station. utility; licensee A body, licensed by the Energy Regulatory Commission, that generates, transmits or distributes electricity. Such a body might be the direct licensee, or an agent (sub-distributor) of the licensee. validation The process of checking the data integrity of a message, or selected parts of a message varistor A resistor whose resistance is dependent on voltage voltage deviation The difference, generally expressed as a percentage, between the voltage at a given instant at a point in the system, and a reference voltage such as nominal voltage, a mean value of the operating voltage, or declared supply voltage voltage dip A sudden reduction in the r.m.s. voltage, for a period of between 20 ms and 3 s, of any or all of the phase voltages of a single-phase or a polyphase supply. The duration of a voltage dip is the time measured from the moment the r.m.s. voltage drops below 0.9 per unit of declared voltage to when the voltage rises above 0.9 per unit of declared voltage voltage drop probability level ( p) The probability (p.u. or percentage) that, at the design load, the voltage drop measured at the point of supply, for a customer connected at the end of the heaviest loaded circuit of the system under consideration, will be within the required voltage drop limit.

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NOTE 1 The opposite of voltage drop probablility level is voltage drop risk level. NOTE 2 The designer's choice of the voltage drop probability level will be influenced by his confidence that the load will have the characteristics of the chosen beta (β) distribution function. voltage drop risk level See voltage drop probability level. voltage flicker The modulation of the amplitude of the supply voltage, perceived by the observer as a fluctuation of light intensity in electric lighting voltage harmonics Sinusoidal components of the fundamental waveform (i.e. 50 Hz) that have a frequency that is an integral multiple of the fundamental frequency Odd harmonics are defined as the 3rd (150 Hz), 5th (250 Hz), ... etc. Even harmonics are defined as the 2nd (100 Hz), 4th (200 Hz), ... etc. Interharmonics are frequency components that are not an integral multiple of the fundamental frequency. Total harmonic distortion (THD) is given by:

∑−

=N

hhVTHD

1

2

where

Vh is the per cent r.m.s. value of the hth harmonic or interharmonic voltage component, and N is the highest harmonic considered in the calculation.

voltage regulation (of a power network) The percentage change to the output voltage of a device when a load is applied to the output and based on the voltage before the load was applied voltage regulation (of power supply equipment) The percentage change to the output voltage of a device when a load is applied to the output and based on the voltage before the load was applied voltage transformer An instrument transformer in which the secondary voltage, in normal conditions of use, is substantially proportional to the primary voltage, and differs in phase from it by an angle which is approximately zero for an appropriate direction of the connections. voltage unbalance Voltage unbalance arises in a polyphase system when the magnitude of the phase voltages or the relative phase displacements of the phases (or both) are not equal NOTE This definition is an abridged form of the definition in NRS 048-1, which includes the formulae for calculating voltage unbalance. watt-peak power The maximum power, in watts, that a photovoltaic module can deliver under standard test conditions weak link (in the context of aerial bundled conduct or (ABC) fittings) A fitting that can be fitted between the pole fitting and a suspension fitting and that is designed to fail at a predetermined load, generally less than the breaking force of the ABC or of the suspension fitting weather stabilized Modified by methods such as carbon loading to withstand ultraviolet radiation and the effects of temperature, humidity and wind wind span (of an overhead line)

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The sum of those portions of span lengths on either side of the structure that, when subjected to wind, impose a horizontal load on the structure NOTE The maximum wind span is dependent upon the ability of the structure and its foundation to resist the overturning moment caused by the action of the wind. wiping gland body A non-ferrous metal bush to which the metal sheath of the cable is plumbed, to which the armour is clamped and which seals and secures the cable to the enclosure withstand voltage The value of the test voltage that is to be applied under specified conditions in a withstand test, during which a specified number of disruptive discharges are tolerated

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