59269522 module 5 mv switch testing

7/27/2019 59269522 Module 5 MV Switch Testing

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EITCA Acceptance Testing and Commissioning Training Course

Module 5: MV Air Switch acceptance tests

TABLE OF CONTENT

Headings Page

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IntroductionThis module will introduce the NETA acceptance testing procedures for switchescomprising of mechanical and visual inspections, electrical tests and test dataanalysis.

An understanding on the theory of operations, functions, types, industry ratingsand typical applications will be useful when performing acceptance testing. Thediscussion will focus on the medium voltage, three-phase indoor and outdoor air

break switches, rated at 60 Hz found in substations. Oil, vacuum, SF6 anddistribution class switches and switches provisioned with series interrupters will bedeveloped as a sub set to this module in the future.

By the end of this module the participants should be able to differentiate thedifference between isolating, load breaking and load making switches of the fusedor un-fused types. General testing procedures for the blade type air break switcheswill be presented. Where more detailed instructions are required, the reader shouldconsult the manufacturers manuals.

By the end of this module the participants will have the basic skills to performacceptance testing on blade type air break switches, conduct visual and mechanicalinspections, insulation resistance tests, dielectric withstand test, contact resistancetest and completing the inspection / test forms and conduct an assessment of thetest data.

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1. North American HV Switch StandardsThe principle North American AC high voltage switch standards in use today arethe US standards comprising of the ANSI/IEEE, and NEMA standards.

There are no existing Canadian CSA standards for HV switches dealing with ratingor application guidelines / specifications. The applicable CSA standards are safety

practices dealing with HV equipment installation covered by the CanadianElectrical Code.

The principle ANSI/IEEE standards are: IEEE C37.30 Standard Requirements for High Voltage Switches ANSI C37.32 High Voltage Switches, Bus Support and Accessories

IEEE C37.34 Standard Test Code for High Voltage Air Switches NEMA SG 6 Power Switching Equipment

The basis for preferred ratings for indoor and outdoor air switches is covered inIEEE C37.30-1997; Standard Requirements for High Voltage Switches.

Refer to Table 1:

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Table 1: North American High Voltage Switch StandardsSTANDARD REV SPONSOR TITLE WORKING

GROUPC37.30 1997 ANSI /

IEEEStandard Requirements for High Voltage Switches IEEE

C37.32 2002 ANSI Standard for High Voltage Switches, Bus Support, andAccessories

IEEE / NEMA

C37.34 1994 IEEE Standard Test Code for High Voltage Air Switches IEEE

C37.58 2003 ANSI Conformance Test Procedure for Indoor AC Medium-VoltageSwitches for Use in Metal-Enclosed Switchgear

NEMA

SG-6 2009 NEMA Power Switching Equipment NEMA

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1.1 Rated CharacteristicsSwitch ratings are the designated limits of rated operating characteristics of thedevice for operating at the rated power frequency.

Common designated ratings: Maximum voltage Dielectric withstand Power frequency Continuous current Peak-withstand and short time withstand current Making current Closing time Ice breaking ability Mechanical operations Mechanical terminal load Load-interrupting current Unloaded transformer interrupting current Expected switching endurance

Maximum VoltageThe rated maximum voltage is the highest rms line-to-line voltage at which theswitch is designed to operate.Refer to table 2, 3 and 4.

Switches are selected on the basis of the rated maximum voltage and the lightningimpulse withstand voltage. The open gap withstand voltage value is at least 110%of the phase-to-ground voltage value to ensure that overvoltage condition willflashover to ground instead of flashing across an open switch gap distance.

Switches constructed with insulators having a rated phase to ground voltage

insulation level higher than the open gap withstand voltage level should be fittedwith surge arresters adjacent to the equipment to prevent open gap flashovers.

Dielectric Withstand VoltageThe rated dielectric withstand voltage is the voltage that the switch shall withstandwhen the voltage is applied under the following specified conditions:

Rated Lightning-impulse withstand voltage 1.2 x 50 s positive and

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negative withstand voltage Rated power frequency dry withstand voltage Rated power frequency wet withstand voltage Rated Power frequency dew withstand voltage (enclosed switchesonly)

The selection of the insulation level is a function of the device surge protection.

Table 2: Preferred Voltage Rating for Station Class Outdoor AirSwitches

Rated Maximumvoltage

kV rms

Lightningimpulse

kV peak

Rated withstand voltageDry

1 minute

Wet

10 second8.3 95 38 30

15.5 110 50 4527 150 70 6038 200 95 80

48.3 250 120 100

Table 3: Preferred Voltage Rating for Distribution Class Outdoor AirSwitches

Rated MaximumvoltagekV rms

LightningimpulsekV peak

Rated withstand voltageDry1 minute

Wet10 second

8.3 75 28 2415.5 95 38 3027 125 60 5038 150 70 60

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Table 5: Grounding Switch ElectricalClearances and Voltage Ratings

Rated MaximumVoltage

Minimum Gap groundswitch to live parts

kV rms mm inchesIndoor

4.8 51 28.3 51 2

15.5 51 227 75 338 102 4

Station Class Outdoor 8.3 51 2

15.5 51 227 102 438 152 6

48.3 241 9.5

Peak-Withstand CurrentThe rated peak-withstand current rating is the maximum instantaneous current at

the first major peak with a duration not less than 167 milliseconds that the switchshall be required to carry while closed. The dc component of this current shallhave a decay time constant not greater that 45ms for a system X/R ratio of 17.

Note: Refer to module 4 for an explanation of %DC rating of circuit breakerswhich shows the decay curve for power system with X/R ratio of 17.

The rated peak-withstand current rating is the ability of the switch to withstand themagnetic forces generated by the short-time current without being forced openwhile in the closed position.

Short-time Withstand CurrentThe rated short-time withstand current rating is the maximum rms current insymmetrical amperes that the switch shall be required to carry for the rated short-time duration while closed.

The rated short-time withstand current rating is the ability of the switch to

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withstand the heat generated by the short-time current.

The ratio of peak-withstand current to the short-time current is 2.6 at 60 Hz.

Short-time Withstand Current DurationThe rated short-time withstand current duration is the time in seconds that switchshall be required to carry the short-time current while closed. Refer to table 6.

Table 6: Preferred Continuous and Withstand Currents for StationClass Outdoor Air Switches

Continuous CurrentAmperes

Short-time currentkA

Peak current 1

kA

600 25 631200 38 951600 44 1102000 44 1102000 63 1583000 63 1583000 75 1884000 75 188

1. Peak withstand current (kA) 2.625 times the rms asymmetrical momentary current (kA).

Table 7: Preferred Continuous and Withstand Currents for DistributionClass Outdoor Air Switches

Continuous CurrentAmperes

Short-time currentkA

Peak currentkA

200 or 600 12.5 32.5600 or 1200 25 65

1200 38 99

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Table 8: Preferred Continuous and Indoor Air SwitchesContinuous Current

AmperesShort-time current

kAPeak current

kA200 or 400 12.5 32.5

600 25 651200 38 992000 50 1303000 63 1644000 75 195

Load making Current

The rated load making current is the highest rms current that the switch shall berequired to make and carry at the maximum rated voltage.

Load interrupting CurrentThe rated load interrupting current of a load-break switch is the highest rmscurrent, in amperes, between unity and .7 power factor that a device shall berequired to interrupt without requiring maintenance at its rated maximum voltagefor a number of operations equal to its expected switching endurance for this duty.

Note: High voltage disconnecting switches, grounding switches and horn-gapswitches are given no interrupting rating. Low levels of current may beinterrupted as per standard guidelines (IEEE C37.36b). Interrupter switchesfitted with interrupting chambers (e.g. Vacuum, Oil, SF6) may have varioustypes of interrupting ratings dependent upon application duty.

Fault making CurrentThe rated fault making current is the maximum symmetrical rms current that theswitch shall be required to make and carry.

Closing TimeThe rated closing time is the specified interval between the energization of theclose coil and the making of the current-making switch contacts with an operatingcondition at the lower limit of the rated control voltage range.

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Ice-Breaking AbilityThe rated ice breaking ability is the maximum thickness of ice deposited that willnot interfere with its opening and closing function.

Mechanical OperationsThe rated mechanical operations is the minimum number of operating cycles thatcan be perform without requiring readjustment or parts replacement. The specifiednumber of operating cycles is relative to the terminal loading.

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2. Nameplate DataThe general nameplate data show the minimum requirement for equipmentinformation.

Air switches nameplate data shall include the following where applicable: Manufacturers name and address Manufacturers type, designation number and serial number Month and year of manufacture Rated power frequency Rated maximum voltage Rated continuous current Rated short time (symmetrical) withstand current magnitudes and duration Rated peak-withstand current Rated lightning impulse withstand voltage (BIL) Allowable continuous current Rated making current Rated closing time Rated no load mechanical operations

Information specific to the device functionality such as interrupter switches or faultinitiating switches will include rated switching values:

Rated capacitance-switching overvoltage ratio Rated maximum differential-capacitance voltage Rated load-interrupting current and expected switching endurance Rated unloaded transformer interrupting current and expected switching

endurance Rated parallel-connected capacitance-switching current and expected

switching endurance Expected switching endurance at rated making current

- Rated load-interrupting current

- Rated unloaded transformer interrupting- Rated parallel-connected capacitance-switching current- Rated single capacitance interrupting current

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3. SwitchA switch is a mechanical device that makes and breaks the flow of electrical power and is used to change connections in a circuit or isolate a circuit from its power source.

A switch consists of one or more contacts per phase mounted on an insulatingstructure and arranged so that they can be moved into and out of contact with eachother by a suitable insulated operating mechanism.

General purpose switches are used to perform the following functions: Carry normal current continuously Switching of mainly active loads Switching of distributive line in a closed loop circuit Switching of no-load transformers Switching of charging current for unloaded cables or overhead lines Carrying short circuit currents for a specified duration Making short circuit currents

Special purpose (interrupter) switches can have designed applications for: Switching single capacitor banks Switching back-to-back capacitor banks Switching closed loop circuit having large power transformers in parallel Switching motors under steady state and stalled conditions Switching into a fault condition

Closing into a faultSwitches are not designed to interrupt fault current. This is a major functional /design difference between a switch and a circuit breaker.

Switches can be operated to close following a breaking operation but cannot be

operated to open following a closing operation since the rated breaking current of the switch may be exceeded.

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3.1 Switch TypesSwitches can be broadly classified into:

Disconnect switch Load break switch Interrupter switch Ground switch Fault initiating switch

3.1.1 Disconnect SwitchDisconnect switches are designed for no load switching and opening of circuitswhere negligible currents are interrupted. Disconnect switches are slow-speedoperating devices and not designed for arc interruption. Interlocking hardware /

controls are commonly installed to prevent opening under loaded conditions.Disconnect switches can be fitted with arc whips to increase its load breakingcapability for transformer magnetizing currents and line charging current

Figure 1: Southern States Outdoor Disconnect Fitted With Arc Whip

Disconnect switches are designed to carry rated load currents and can momentarilycarry short circuit currents until the associated protective devices have operatedand trips the associated circuit breaker(s).

An open disconnect switch provides a visible confirmation that the circuit have been opened and serves as an approved isolation point. When all the sources of

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primary energy have been remove and all required switches have been opened andequipment de-energized and isolated, working safety grounds can be applied to thede-energized equipment.

Motor OperatorMotor operated disconnect switches are fitted with a geared motorized operator which can be decoupled by a selector handle so that a manual operator can beengaged to operate the switch. Selector handle positions are Manual-Off-Motor.

Figure 2: General Switchgear Type MSO motor operator

Motor operator are commonly associated with outdoor switches but can be fittedinto metal enclosed switch units. Their design and configuration are more compactsince it must be fitted within the confines of the enclosure space. Indoor motor operator drive the same operating shaft though a clutch coupled shaft where themotor exert the force requires to operate the operating shaft.

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Figure 3: General Electric Motor Operator for Masterbreak Switch

3.1.2 Load Break SwitchLoad break switches are designed for breaking normal load currents. Load currentinterruption is accomplished with the inclusion of arc interrupting hardware and aquick make / quick break operating mechanism.

E.g. Spring assisted quick-break arcing contact and arc chute.

The quick-make operation provides the rated fault closing ability and the quick- break provides the rated load interrupting ability. The breaking rating is usually thesame as the continuous current rating, never greater but sometimes lesser.

Arc interruption hardware can comprise of: Air puffer by compressed pistons Arc chutes and spring assisted arcing contacts Other arc interrupting technology

The operating mechanism consists of powerful opening / closing springand an off-center mechanism. The switch operating shaft is either direct driven bya side mounted operating handle or driven by front mounted operating handle viachain drive and sprocket. When the handle is rotated, it rotates the operating shaftand charges the spring. Continued rotation of the shaft will drive the spring off-

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center and releases its energy rotating the shaft in a single snap action. Once thesprings are moved off-center, the operator has no control of the opening or closingoperation.

Other mechanisms can be fitted to most load break disconnect to accommodate:Motor operated tripping and closingShunt tripping and closingMechanical fuse tripping

Figure 4: General Electric Load Break Switch

3.1.3 Interrupter SwitchInterrupter switches are switches which have been provisioned with interrupter units having a load interrupting rating. Current interruptions are performed by theinterrupters without external arc after the main current carrying contacts haveseparated.

During the opening cycle, as the blades begins to open, current is transferred to theinterrupter unit before the main contacts part. Continued opening of the blades willtoggle the interrupters mechanism resulting in contact opening in the interrupters.

During the closing cycle the blades and interrupters are sequenced to ensure thatcurrent is picked up by the fault closing main contacts and not by the interrupter

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units. Once the main contacts are closed, switching mechanism will reset and closethe interrupter contacts and readies it for the next opening cycle.

3.1.4 Grounding SwitchGrounding switches are used for grounding purposes and may be used in single

pole of group operated arrangement. Ground switch has no continuous currentrating but has a fault current endurance rating and are manually operated.

3.1.5 Fault initiating SwitchFault initiating switch is a high speed grounding switch with a rated fault makingcurrent rating.

The switch closing can be performed by: High speed, high torque motor Unlatching a spring charged mechanism

The switch opening can be performed by: High speed, high torque motor Manually

Fault initiating switches are used for on transformer protection scheme which lacksan incoming breaker. During a transformer fault, the transformer protectioninitiates closing of the switch simulating a phase-to ground fault on the line so thatremote line protection schemes will operate and trip its breaker(s).

Fault initiating switch can be fitted with a disconnect switch for testing andmaintenance.

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Figure 6: Joslyn Outdoor Center and Double End Break DisconnectSwitches

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4. Glossary of Terms

4.1 Switch Types

Air SwitchA switch in which the air is used as the dielectric medium between the opencontacts (e.g.air break switch).

Center Break SwitchA switch with two rotating insulators, located at each end of the base. The rotationof the insulators causes the blade and contact to make / break at a pointapproximately in the center between the insulators.

Disconnect SwitchA disconnecting switch is an air switch used for changing connections in a circuitor system, or used for isolating purposes. It is intended to be operated under no-load condition as it has no interrupting rating.

Double Break SwitchA switch with a center rotating insulator column supporting a conducting rodequipped with moving contacts at both ends. The center insulator column rotates tomake / break with the fixed contacts mounted on two insulator columns to engagethe moving contacts.

Load Interrupter SwitchA switch having a rated current interrupting rating equal to the continuous currentrating of the switch at rated maximum voltage. Arc interruption technology isincorporated into the switch design (e.g. arc chutes / auxiliary blade or air blast).

Fused Disconnect switchA switch and fuse unit in which a fuse or fuses is connected in series with the

switch on each phase. The fuse in connected on the load side of the switch for which the downstream side becomes the load terminal.

Grounding SwitchA switch which has the load side connected to earth for the purpose of groundingthe circuit where the line side is connected to. A ground switch has no currentrating.

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Sectionalizing switchA switch used for the function of sectionalizing part of a circuit (e.g. bus or feeder). Bus sectionalizers are three-pole devices and normally operated in theclosed position. Feeder sectionalizers can be single phase or three phase devices(e.g. oils switch).

Side Break SwitchA switch possessing moving parts which operates in a plane parallel to the base of the switch.

Single Break SwitchA switch which opens at one point only is a single break switch.

Tilting Insulator SwitchA switch in which the opening and closing travel of the blade is accomplished by atilting movement of one or more of the insulators supporting the conducting part of the switch.

Vertical Break SwitchA switch possessing moving parts which operates in a plane perpendicular to the

base of the switch.

4.2 Operation

Direct OperationDirect operation of a mechanically operated switch is the operation by means of amechanism connected directly to the main operating shaft, or an extension of it.

Group OperationGroup operation of a multi-pole switch is the operation of all poles by means of one operating mechanism.

Hook OperationHook operation of a switch is the operation manually by means of a switch hook.

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Indirect OperationIndirect operation of a switch is the operation by means of an operating mechanismconnected to the main operating shaft, or an extension of it, through offset linkageand bearing.

Manual OperationManual operation of a switch is the operation by hand without using any other source of power.

Mechanical OperationMechanical operation of a switch is the operation by means of an operatingmechanism connected to the switch by mechanical linkage. The operating

mechanism may either be hydraulic, pneumatic, or a combination of both. Themechanical operation of a switch may be actuated either manually, or electrically,or by other suitable means.

Operating MechanismThe operating mechanism of a switch is a power operated or manual mechanism bywhich the contacts of all poles are actuated.

OperationThe operation of an air switch is the method provided to perform its normalfunction, that of opening or closing.

Power OperationPower operation of a switch is the operation by power, such as motor operator,spring operator, pneumatic operator, or hydraulic operator.

Remote Controlled OperationRemote controlled operation of a switch is the operation by means of an operatingmechanism controlled from a distant point either manually and/or electrically or by

other means.

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4.3 Construction & Parts

Arcing Contacts (Arcing Horns) (Parking Horns)Arcing contacts are the contacts on which the arc is drawn after the main contactsof a switch have parted.

BaseA base of a switch is the main member to which the conducting parts or insulator unit are attached. It may also have parts of the operating or control mechanismattached.

Bell Crank or Outboard Bearing

A bell crank is a lever with two or more arms placed at an angle diverging from agiven pivot point, by means of which the direction of motion of a mechanism ischanged.

Bell Crank HangerA bell crank hanger is a support for a bell crank.

BladeA switch blade is the moving contact member which moves to engage or disengagethe conductors.

Blade GuideA blade guide of a switch is an attachment to secure proper alignment of blade andcontact when closing the switch.

Blade LatchA blade latch is a latch used on a switch to hold the switch blade in the closed

position.

ClevisA clevis is a fitting having a U-shaped end and arranged for attaching to the end of a pipe or rod.

ContactThe contact is a conducting part designed to be united by pressure to another conducting part for the purpose of carrying current.

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Contact SurfacesContact surfaces are the surfaces of contacts which meet and through which thecurrent is transferred when the contacts are closed.

Current Carrying PartsCurrent carrying part is a conducting part intended to be connected in an electriccircuit to a source of voltage.

Extended Outrigger ClampAn extended outrigger clamp is an attachment fastened to the terminal pad of aswitch to which the conductor is clamped to relieve mechanical strain on the

terminal.Inter-phase Connecting RodsInter-phase connecting rods are the rods connecting the several poles of a switchtogether, and to the operating rods.

Live PartsLive parts are those parts which are electrically connected to points of potentialdifferent from that of the ground.

Moving Contact MemberA moving contact member of a switch is a conducting part which bears a contactsurface that moves to and from the stationary contact.

Operating RodsOperating rods are connected to the moving contact which deliver the rated forceand speed required for proper operation of the switch.

OutriggerAn outrigger is an attachment which is fastened to or adjacent to the terminal pad

of a switch and to which the conductor is clamped to relieve mechanical strain onthe terminal and/or to maintain electrical clearance between the conductor and thegrounded parts.

Pipe End (Rod End)A pipe end is a fitting arranged to connect the end of a pipe or rod to a lever, bellcrank, or other part.

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PoleA pole of a switch consists of the parts necessary to control one conductor of acircuit. A switch may be single pole or multi-pole, depending upon the number of single poles that are operated simultaneously.

Sleet HoodA sleet hood of a switch is a cover for the contacts to prevent the accumulation of sleet from interfering with the successful operations of the switch.

Stationary Contact MemberA stationary contact member of a switch is a conducting part which bears a contact

surface that remains stationary.

Switch MechanismA switch mechanism is an assembly of levers and other parts which actuate themoving contacts of the switch.

Terminal PadA terminal pad of a switch is the extension provided on the switch to which theterminal connection is fastened.

Wire GuideA wire guide is an attachment to maintain a conductor in a definite position withrelation to the switch.

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4.4 Miscellaneous Terminology

ClearanceClearance is the minimum distance between two conductors, between conductorsand supports or other objects, or between conductors and ground.

CoronaCorona is a luminous discharge due to ionization of the air surrounding aconductor around which a voltage gradient exists exceeding a certain critical value.

Drip-proof Drip-proof means go constructed or protected that its successful operation is not

interfered with when subjected to falling moisture or dirt.

Drip-tightDrip-tight means so constructed or protected as to exclude falling moisture or dirt.

GroundA ground is a conducting connection, between an electric circuit or equipment andearth, or to some conducting body which serves in place of' the earth.

GroundedGrounded means connected to earth or to some conducting body which serves in

place of the earth.

Grounded PartsGrounded parts are those parts which are so connected that, when the installation iscomplete, they are substantially of the same potential as the earth.

Insulator Unit (Insulator Stack)The insulator unit of an air switch is the insulating part or assemblies that isolates

the current carrying parts from ground.

Interlock An interlock is a device actuated by the operation of some other device with whichit is directly associated, to govern succeeding operation of the same or allieddevices.

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Minimum Clearance Between PolesThe minimum clearance between poles is the shortest distance between any live

parts of adjacent poles.

Minimum Clearance to GroundThe minimum clearance to ground is the shortest distance between any live partand adjacent grounded parts.

Phase SpacingThe phase spacing of air switches is the distance between centers of the live partsor conductors of one pole and the current carrying parts of an adjacent pole.

Quick Break A switch is quick break when it has a high contact opening speed independent of the operator.

Quick makeA switch is quick make when it has a high contact closing speed independent of theoperator.

Spark GapA spark gap is an arrangement of two electrodes between which a disruptivedischarge or electricity may take place, and such that the insulation is self restoringafter the passage of a discharge.

Switch Hook A switch hook is a hook provided with an insulating handle for opening andclosing hook operated switches.

Voltage to Ground

The voltage to ground is the voltage between any live conductor or a circuit andthe earth.

WatertightWatertight means provided with an enclosing case which will exclude water applied in the form of a hose stream for a specific time.

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Weatherproof - (Outdoor)Weatherproof means so constructed or protected that exposure to the weather willnot interfere with its successful operation.

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5 Switch Testing

Note: The testing procedures described in this module are for air switches having blade contacts of the station class, indoor and outdoor type or of the metalenclosed type. The procedures are general in nature and it does notdifferentiate the nuances in the various type of switch design. Task stepswhich are not applicable to the respective switches should be treated as notapplicable.

The test procedures can also be applied for distribution class, switch hook operated air switches.

Note: Always wipe and clean any apparatus before performing any high voltageinsulation / resistance test, with a lint free rag.

Note: Mechanical and electrical testing go hand in hand in the testing of switches.High contact resistance value requires mechanical adjustments. Mechanicaladjustments requires electrical testing to confirm if the adjustments are

performed correctly

5.1 Safety Considerations

5.1.1 High Voltage SafetyMany of the tests involve the use of high voltage test equipment; testing should be

performed by qualified personnel familiar with the test set operations and thehazards associated with the tests.

Refer to Module 2 for Safety Working Practices and Guidelines.

Refer to IEEE Standard 510 1983, Recommended Practice for Safety in HighVoltage & High Power Testing.

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5.1.2 Electrostatic ChargeAfter any high potential voltage is removed, an electrical charge may be retained

by the insulating bushing. Failure to discharge the residual electrostatic chargecould result in an electrical shock. Always ground the last test point before movingthe test set high voltage lead.

5.1.3 Stored Energy

Fault Initiating SwitchFault initiating switches can rely on the release of stored energy devices for itsclosing functions. Stored energy devices typically consists of a spring chargedmechanisms with a release latch, which could be electrically unlatched. Care

should be taken to isolate the secondary controls to prevent inadvertent unlatchingwhen working on the equipment.

Load break SwitchLoad break switch uses charged spring energy to produce the required quick-make / quick-break operations. Foreign material such as test leads and tools should

be removed from the enclosure prior to performing any closing or openingoperations.

5.1.2 Working at HeightsOutdoor and indoor open-type station class switches are typically mounted with ahigh ground clearance as required for station design and to be in-line with the busstructure. Access to the switches will require working at elevated levels. Anyoneworking at elevated level should be trained for working at heights and use therequired fall arrest / restraint gear, erect warning signs and obtained the required

permit if applicable.

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5.2 Mechanical Testing:The mechanical testing of switches is detailed in its scope and if performed

properly will contribute to the reliability and long operating life of the switches.

Mechanical testing consists of: Mechanical inspection Manual operations

5.2.1 Mechanical InspectionThe purpose of the mechanical inspection is to:

Verify the ratings matches the design specifications Verify the installation

Determine any damages resulting from installation / transport

Items for inspection checks are: Examine insulators for cracks or defective parts Check and lubricate contacts as recommended by the manufacturer Examine locks for security, function and ease of operation Check the operating mechanisms Check for lost motion or binding of the operator Check adjustment of horns on horn-gap switches Check break distances, clearances between live parts and travel of all

switches. Check phase-to-phase and phase-to-ground clearances between live parts or

between the switching equipment and adjacent structures

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Mechanical Inspection Procedure1. Confirm the nameplate rating with the contract specification, bill of material list

or applicable drawings / one line diagrams / three line diagrams.

3. Confirm that the cubicles or frame are properly grounded.

4. Confirm that the cubicles / structures are installed level and plumb.

5. Inspect the switch for signs of damage during shipping or installation.

6. Check the support bushing or column insulators for any signs of chipping or cracking.

7. Ensure that the correct switch is in the correct location / position.

8. Check the required clearance and cable drop distance requirements as per manufacturers manual.

9. Verify tightness of accessible bolted electrical connections by calibrated torque-wrench method in accordance with manufacturers published data or Table 2 of module 2.

10. Confirm fuse size, type and rating as per bill of material list or applicabledrawings / one line diagrams / three line diagrams.

11. Record as found / as left counter readings

5.2.2 Manual Operations TestThe purpose of the operations test is use to check:

The manual operator is working properly The switch is adjustments correctly

The manual operations tests consist of: Manual operator test

Main Blade and Auxiliary Contact Alignment Check Contact Pressure Checks Mechanical Safety Interlock Test Motor Operator Auxiliary / Limit Switch Test

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Types of outdoor manual operators: Rotating hand wheel (outdoor) Rotating crank / lead screw or worm gear drive (outdoor) Torsional direct drive hand operator (outdoor)

Types of indoor manual operator: Side mounted operating handle Front panel mounted operating handle (indoor)

For outdoor motor operated disconnect switches, the motor operator must bedisengaged /decoupled when performing a manual operations test. Motor operated

switches are provided with a Manual-Off-Motor selector handle. The selector handle must be moved to the Manual position.

Placing the selector handle to the Manual position performs two functions: Disengages the motor from the gear train by disconnecting anintermediate gear clear off its mesh with the mating gear Opens a cut-out switch in the motor power circuit

For outdoors / indoor metal enclosed switches, the locking pin must be pulled to permit rotation of the operating handle. The pin must be pulled, turned and set on araised shoulder. Placing the locking pin on the shoulder will unlock the operatinghandle. Putting the locking pin back into the housing will block the operatinghandle.

Manual Operations Test Procedure

Note: Perform a three-phase slow close operation by removing the spring tubeassembly containing the main spring and drive plunger.

The spring tube assembly is removed by removing the outside cotter pinsecuring the spring tube assembly to its pivot pin. The main spring isdischarged when the switch is in the Open or Close positions.

Refer to figure 8, Powercon P.I.F. Mechanism Explode View Diagram

1. Remove / isolate all control power to the:

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Shunt trip device Local / remote motor control circuit Local / remote indication circuit

2. Perform a slow Close operation until the blades enter or touch the stationary jaw contacts.Verify the following:

The moving contacts to fixed contacts alignment The auxiliary contact to arc chute alignment Arcing contacts make before main contacts Moving contacts are synchronized

Note: Refer to procedure 5.2.4.1, Manual Operator Test Procedure which detailsthe requirement for performing contact resistance test as a critical part of themechanical testing.

3 Close the switch until the moving contacts are fully inserted into fixed contactor until mechanical stops are encounteredVerify as per manufacturers manual. Penetration depth for knife blade switches Penetration depth for auxiliary contacts

4. Verify limit switches / auxiliary contacts in the fully Close position Motor Close stop limit switch / contact Motor Open stop limit switch / contact Close indication limit switch / contact Open indication limit switch / contact

5. From a Close position, perform a slow Open operation until the main contactsdisengage from the stationary contacts.Verify the following: Auxiliary /arcing contacts are connected. Moving contacts are synchronized

6. Verify limit switches / auxiliary contacts in the Just-Open position Motor Close stop limit switch / contact Motor Open stop limit switch / contact

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Close indication limit switch / contact Open indication limit switch / contact

7. Verify the moving to stationary contact distance when the auxiliary contact /arcing contact exits the arc chute as per manufacturers manual.

8. Verify the switch final Open position as per manufacturers manual.

9. Verify limit switches / auxiliary contacts in the fully Close position Motor closing stop limit switch / contact Motor opening stop limit switch / contact Close position limit switch / contact Open position limit switch / contact

10.From an Open position, perform a slow Close operation until the movingcontacts just leave the fully Open position.

11.Verify limit switches / auxiliary contacts in the Off-Open position Motor closing stop limit switch / contact Motor opening stop limit switch / contact Close position limit switch / contact

Open position limit switch / contact

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5.2.4.1 Manual Operator Test Procedure:1. Operate the switch several times checking for main blade and arcing bladealignment. Open and close the switch 2-5 times in succession.

2. Ensure that the switch moves freely and that there is no evidence of stickiness or binding.

3. Measure the main contact resistance at the stationary jaw / moving contacts points and at the hinge contact location.

Note: An overall resistance tests can be substituted by measuring the resistance between the load and line side spade terminals with the main contacts close

on a per pole basis. Measuring the individual resistance value at thestationary jaw / moving contacts points and at the hinge contact location is amore detail tests.

4. Ensure that resistance values are within the manufacturers specified range.

5.2.4.2 Main Blade and Auxiliary Contact Alignment Check Main blades and auxiliary contacts alignment check can be performed on anindividual basis. The insulating operating rods (or pushrods) can be disconnectedfrom the main crank by removing the cotter pins and the clevis pins.

The main blades can now be operated by hand to check: Blade alignment / penetration Auxiliary (or arcing contact) alignment / penetration

Main Blade and Auxiliary Contact Alignment Adjustment Procedure

Note: The contact alignments are required to be performed by some manufacturer only if the contact resistance values are not within the specified range. This

writer recommends that contact alignment test procedure be performed evenif the resistance values falls within specified range.

1. Disconnect the pushrods by removing the cotter pins and the clevis pins thatconnects the insulating push rods to the main operating crank arms of each pole.

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Table 9: Figures for Switch Alignment Test ProceduresStep 1

Removing Cotter pin and clevis pin

Step 2,3 and 4

Main blade and jaw casting alignment

Step 4a

Hinge casting bold adjustment

Step 5 and 5a

Jaw casting & spade terminal boltadjustment

Step 6 and 6a

Arc chute adjustment

Step 6b

Arcing blade set screw adjustment

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5.2.4.3 Contact Pressure ChecksThe contact pressure checks can be performed on an individual basis after thecontact alignment procedure has been completed, with the pushrods disconnectedfrom the main crank arm.

Contact pressure adjustments are performed at two contact points: Hinge Contacts Jaw Contacts

Contact Pressure Adjustment Procedure

Note: The contact pressure adjustments are required to be performed by some

manufacturer if the contact resistance values are not within the specified range.This writer recommends the contact pressure adjustment procedure be performedeven if the resistance values falls within the specified range.

1. Open the switch until the arcing blade just clears the arc chute.

2. Connect a spring scale to the main blades approximately 1.5 below the jawcontact or connect to the spacer between the main blades if it is present.

Note: A Tee adapter may have to be used if there is no spacer or if the spacer is too fart from the jaw contact location.

3. Verify the pulling force required to overcome the hinge contact resistance as per manufacturers specifications.

a. If necessary to adjust, loosen or tighten the hinged bolt as necessary toobtain the required pulling force for moving the main blades.

4. Close the main blades and set it fully into the jaw contact assembly.

5. Verify the pulling force required to dislodge the blades from the jaw contacts as per manufacturers specification.

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Table 10: Figure of Scale Placement For Pressure Adjustment MeasurementStep 2,3 and 3a

Hinge pressure measurementusing 10 pound scale

Step 4 and 5

Jaw Pressure measurement using50 pound scale

Step 4 and 5

Jaw Pressure measurement using50 pound scale

5.2.4.4 Mechanical Safety Interlock Test

Door Interlock The door interlock prevents the door of the enclosure from being opened when theswitch main blades are in the Close position. When the operating handle is in the

Close position, it captures the door latch and prevents the door from being opened.

Switch interlock The switch interlock prevents closure of the switch when the enclosure door isopen. When the door is open and the handle is in the Open position, a pushrod isinserted into a notch in the operating handle mechanism preventing the handlefrom being moved to the Close position.

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Caution: It is recognized that the switch interlock must be defeated to allow themanual operating handle to function to operate the switch for testing

purposes. No equipment / test lead or personnel should be within theenclosure space when the switch is being operated.

Key Interlock Key interlock prevents the operation of the switchs operating handle as well aslocking the main door in the closed position. The key must be inserted into theinterlock and rotated to retract the locking bolt.

Caution: Do not operate the handle when the interlock bolt is extended as it will

result in equipment damage.

The interlock scheme can be set up for locking the switch in the open or closed position. The key can only be removed when the lock bolt is in a predetermined position, thereby releasing one or more keys for the next step in a sequence.

Mechanical Interlock Test Procedure

Note: The noted procedure is for a key interlock which prevents opening of theswitch until the key interlock is inserted and rotated.

1. With the switch in the Close position, attempt a manual Open operation whenthe key is not inserted in the cylinder unit.Verify that the manual operator is blocked from opening.

2. Insert and rotate the key in the cylinder unit.Verify that the handle is free to operate to open the switch

3. Check that the door interlock is functioning.

Verify that the enclosure door cannot be opened when the switch is Close.

4. Open the switch. Open the enclosure door.

5. Check the switch interlock.

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Motor Operator Auxiliary / Limit Switch Test Procedure

Note: Operate the switch with the manual operator when checking limit switch cantiming setting.

1. Placed the switch in the fully Open position.Verify that the limit switch contacts are set as per contact timing diagram.

2. Rotate the switch in the Close direction until the moving contacts moves about5% from the Open position.Verify that the limit switch contacts are set as per contact timing diagram.

3. Place the switch in the fully Close position.Verify that the limit switch contacts are set as per contact timing diagram.

4. Rotate the switch in the Open direction until the moving contacts moves about5% from the Close position.Verify that the limit switch contacts are set as per contact timing diagram.

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Figure 8: Powercon Corp P.I.F. Mechanism Explode View Diagram

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5.3 Electrical TestingElectrical testing consists of:

Insulation resistance test Dielectric withstand test Contact resistance test Fuse resistance test Fuse holder resistance test Operations test

5.3.1 Insulation Resistance TestThe insulation resistance test is a DC voltage test conducted at 100% of the ratedAC insulation phase-to-ground crest level. The DC equivalent is at 1.414 of the ACRMS rated insulation to ground value.

Note: The above value is higher than the recommended NETA insulationresistance test level. In the opinion of this writer, the higher value is a more

practical level since the insulation will be stressed at the operating value.

Note: For indoor switches, the insulation resistance tests can be combined with theswitchgear insulation resistance test when the switch in directly connected tothe main bus, in the connected position and the contacts closed.

Note: For outdoor switches and indoor open style station class switches, theinsulation resistance tests can be combined overall bus bars when the switchin directly connected to the bus and the contacts closed.

The results of the test serves as a preliminary assessment of the primary insulationsystem to determine if it is should be subjected to the power frequency dielectricwithstand test.

Note: Insulation resistance testing is best performed when the ambient temperatureis at 20 C.

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Figure 6: Insulation Resistance Test Connection Diagram.

Insulation Resistance Test Procedure1. For indoor / outdoor metal enclosed switches, isolate the equipment, apply

working grounds to all incoming and outgoing cables and disconnect allincoming and outgoing cables from the spade terminals. Disconnected cablesshould have sufficient clearance from the switchgear terminals greater that the

phase spacing distance. Use nylon rope to hold cable away from incoming andoutgoing terminals as required.

2. Ensure that the equipment is properly grounded.

3. Close the main contacts.

4. Apply the test voltage at the test duration on phase-A terminals with the frameand all other phases grounded.

5. Record test values

6. Repeat step 5 and 6 for phase-B and phase-C

5.3.2 Power Frequency Withstand TestThe 60 Hz dielectric withstand tests are conducted at 75% of the factory dielectricwithstand test voltage level of the test values given in Table 2, 3 or 4.

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The AC test voltage shall have a crest equal to 1.414 times the RMS valuespecified in Table 2, 3 or 4. The wave shape shall be essentially sinusoidal. Thefrequency shall be within 20% of the rated power frequency. The test voltage is to

be increased gradually from zero at a rate no greater than 1000 V per second toreach the required test value and shall be held there for 1 minute.

Figure7: Vacuum and SF6 Circuit Breakers Dielectric Withstand TestConnection Diagram.

Power Frequency Withstand Test Procedure1. For indoor / outdoor metal enclosed switches, isolate the equipment, apply

working grounds to all incoming and outgoing cables and disconnect allincoming and outgoing cables from the spade terminals. Disconnected cablesshould have sufficient clearance from the switchgear terminals greater that the

phase spacing distance. Use nylon rope to hold cable away from incoming andoutgoing terminals as required.

2. Ensure that the equipment is properly grounded.

3. Close the main contacts.

5. Apply the test voltage at the test duration on phase-A terminals with the frameand all other phases grounded.

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6. Record test values.

7. Repeat step 5 and 6 for phase-B and phase-C.

8. Open the main contacts.

9. Apply the test voltage at the test duration on phase-A incoming terminal with phase-A outgoing terminal and all other phases grounded.

10.Record test values.

11.Apply the test voltage at the test duration on phase-A outgoing terminal with

phase-A incoming terminal and all other phases grounded.

12.Record test values.

13.Repeat step 9 to 11 for phase-B and phase-C.

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5.3.3 Contact Resistance TestThe contact resistance test is performed by injecting a constant 100Adc current

between the incoming and the outgoing terminals on each phase. The voltage dropacross the main contact is read using a 4-wire resistance measurement circuitwhich eliminates the measuring voltage leads wire resistance to obtain the contactresistance value.

The switch contact resistance test should be measured from spade terminal tospade terminal with the switch in the closed position. The best lead placementusing the 4 wire method is to place the current source leads furthest from theresistance to be measured and the voltage measuring leads closest to the resistanceto be measured.

Figure 9: Contact Resistance Measurement Connection Diagram.

Contact Resistance Test Procedure1. Close the main contacts.

2. Connect the +ve current lead at the incoming primary terminal on phase-A andthe ve current lead on phase-A outgoing terminal.

3. Connect the +ve voltage lead at the incoming primary terminal on phase-A andthe ve voltage lead on phase-A outgoing terminal.

Note: Place the voltage leads between the current lead and the main contact.

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1. Connect the first low current DLRO measuring paired leads to one cap of phase-A fuse, ensuring that the current injection probe tip is farthest from thefuse barrel.

2. Connect the second measuring paired leads to the other cap, ensuring that thecurrent injection probe tip is farthest from the fuse barrel.

3. Inject either 1 Adc or 10Adc but not exceeding the fuse current rating.

4. Record test value

5. Repeat steps 1 to 4 for phase-B and phase-C fuses.

5.3.5 Fuse Holder Resistance TestThe fuse holder resistance test is performed by injecting a constant 1 Adc or 10Adc current between end caps of the fuse and the fuse clip assembly or at the

bolting plate. The best lead placement using the 4 wire method is to place thecurrent source leads furthest from the resistance to be measured and the voltagemeasuring leads closest to the resistance to be measured.

Figure 10: Fuse holder /clip Resistance Measurement Connection Diagram

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Figure 11 General Electric Typical Motor Operator Schematic Diagram

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5.3.6 Operations TestThe operations test for a motor operated switch will verify the electrical controlsfor Trip and Close operations, indications and associated electrical interlocks.

Motor operators are provided with a removable manual operating handle that isinterlocked with the electrical controls. The interlock is engaged when the manualhandle is inserted in the operating slot preventing the motor circuit from operating.

Refer to figure 11 for a typical metal enclosed motor operated switch schematic.The actual equipment schematic should be used when commissioning the controlcircuits.

Operations Test Procedure

Note: Consult the manufactures commissioning procedure for the switch drivetype.

1. Confirm power supply polarity and magnitude to the motor operator controlcircuit with the fuse(s) removed.Re-insert the fuse (s) if polarity and magnitude is as per nameplaterequirements.

2. Return the manual handle to the cradle and turn the cradle keylock to capturethe key and close its auxiliary contact.

3. Reset any remote lockout devices connected to terminal M3-M4 in theschematic.

4. Perform a Close operation via the local electrical local / remote controls.Verify switch operation and indications.

5. Perform an Open operation via the local electrical local / remote controls.Verify switch operation and indications.

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6. NETA Switch Acceptance Test Procedure

6.1 Switches, Air, Medium-Voltage, Metal-enclosed

6.1. 1. Visual and Mechanical Inspection1. Compare equipment nameplate data with drawings and specifications.

2. Inspect physical and mechanical condition.

3. Inspect anchorage, alignment, grounding, and required clearances.

4. Verify the unit is clean.

5. Verify correct blade alignment, blade penetration, travel stops, arc interrupter operation, and mechanical operation.

6. Verify that fuse sizes and types are in accordance with drawings, short-circuitstudy, and coordination study.

7. Verify that expulsion-limiting devices are in place on all holders havingexpulsion-type elements.

8. Verify that each fuse holder has adequate mechanical support and contactintegrity.

9. Inspect bolted electrical connections for high resistance using one or more of the following methods:

1. Use of a low-resistance ohmmeter in accordance with Section 7.5.1.2.2.

2. Verify tightness of accessible bolted electrical connections by calibrated

torque-wrench method in accordance with manufacturers published data or Table 100.12.

3. Perform thermographic survey in accordance with Section 9.

10.Verify operation and sequencing of interlocking systems.

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11.Verify correct phase barrier installation.

12.Verify correct operation of all indicating and control devices.

13.Verify appropriate lubrication on moving current-carrying parts and on movingand sliding surfaces.

6.1.2. Electrical Tests1. Perform resistance measurements through bolted connections with a low-

resistance ohmmeter, if applicable, in accordance with Section 7.5.1.2.1.

2. Measure contact resistance across each switchblade and fuseholder.

3. Perform insulation-resistance tests for one minute on each pole, phase-to-phaseand phase-to- ground with switch closed, and across each open pole. Applyvoltage in accordance with manufacturers published data. In the absence of manufacturers published data, use Table 100.1.

4. Perform a dielectric withstand voltage test on each pole with switch closed.Test each pole-to- ground with all other poles grounded. Test voltage shall be inaccordance with manufacturers published data. In the absence of manufacturers published data, use Table 100.2.

5. Measure the fuse resistance.

6. Verify cubicle space heater operation.

6.1.3. Test Values

6.1.3.1 Test Values Visual and Mechanical1. Compare bolted connection resistance values to values of similar connections.

Investigate values which deviate from those of similar bolted connections bymore than 50 percent of the lowest value. (7.5.1.2.1.9.1)

2. Bolt-torque levels shall be in accordance with manufacturers published data. Inthe absence of manufacturers published data, use Table 100.12. (7.5.1.2.1.9.2)

3. Results of the thermographic survey shall be in accordance with Section 9.

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4. Verify the unit is clean.

5. Perform mechanical operator tests in accordance with manufacturers publisheddata, if applicable.

6. Verify correct operation and adjustment of motor operator limit switches andmechanical interlocks, if applicable.

7. Verify correct blade alignment, blade penetration, travel stops, arc interrupter operation, and mechanical operation.

8. Verify operation and sequencing of interlocking systems.

9. Verify that each fuse has adequate mechanical support and contact integrity, if applicable.

10.Verify that fuse sizes and types are in accordance with drawings, short-circuitstudy, and coordination study.

11. Inspect bolted electrical connections for high resistance using one or more of the following methods:

1. Use of low-resistance ohmmeter in accordance with Section 7.5.1.3.2.

2. Verify tightness of accessible bolted electrical connections by calibratedtorque-wrench method in accordance with manufacturers published data or Table 100.12.

3. Perform thermographic survey in accordance with Section 9.

12.Verify correct operation of all indicating and control devices, if applicable.

13.Verify appropriate lubrication on moving current-carrying parts and on movingand sliding surfaces.

14.Record as-found and as-left operation counter readings.

6.2.2. Electrical Tests

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1. Perform resistance measurements through bolted connections with a low-resistance ohmmeter, if applicable, in accordance with Section 7.5.1.3.1.

2. Perform contact-resistance test across each switchblade and fuseholder.

3. Perform insulation-resistance tests for one minute on each pole, phase-to-phaseand phase-to- ground with switch closed, and across each open pole. Applyvoltage in accordance with manufacturers published data. In the absence of manufacturers published data, use Table 100.1.

4. Perform insulation-resistance tests on all control wiring with respect to ground.

Applied potential shall be 500 volts dc for 300-volt rated cable and 1000 voltsdc for 600-volt rated cable. Test duration shall be one minute. For units withsolid-state components or control devices that can not tolerate the appliedvoltage, follow manufacturers recommendation.

5. Perform a dielectric withstand voltage test on each pole with switch closed.Test each pole-to- ground with all other poles grounded. Test voltage shall be inaccordance with manufacturers published data. In the absence of manufacturers published data, use Table 100.19.

6.2.3. Test Values

6.2.3.1 Test Values Visual and Mechanical

1. Compare bolted connection resistance values to values of similar connections.Investigate values which deviate from those of similar bolted connections bymore than 50 percent of the lowest value. (7.5.1.3.1.11.1)

2. Bolt-torque levels shall be in accordance with manufacturers published data. In

the absence of manufacturers published data, use Table 100.12. (7.5.1.3.1.11.2)

3. Results of the thermographic survey shall be in accordance with Section 9.(7.5.1.3.1.11.3)

4. Operation counter should advance one digit per close-open cycle.(7.5.1.3.1.14)

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6.2.3.2 Test Values Electrical

1. Compare bolted connection resistance values to values of similar connections.Investigate values which deviate from those of similar bolted connections bymore than 50 percent of the lowest value.

2. Microhm or dc millivolt drop values shall not exceed the high levels of thenormal range as indicated in the manufacturers published data. In the absenceof manufacturers published data, investigate values that deviate from adjacent

poles or similar switches by more than 50 percent of the lowest value.

3. Insulation-resistance values shall be in accordance with manufacturers

published data. In the absence of manufacturers published data, use Table100.1. Values of insulation resistance less than this table or manufacturersrecommendations should be investigated. Dielectric withstand voltage testsshould not proceed until insulation-resistance levels are raised above minimumvalues.

4. Minimum insulation-resistance values of control wiring shall not be less thantwo megohms.

5. If no evidence of distress or insulation failure is observed by the end of the totaltime of voltage application during the dielectric withstand test, the testspecimen is considered to have passed the test.

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7. Test Set Operational Manual

Low Current DLRO

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8. Test Forms

Open Air Switch Test Form

Metal enclosed Switch Test Form

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Acknowledgement, References and Recommended Reading

Acknowledgement:Special thanks to Morpac Industries, Inc (Mr. John Thames, General manager)who allowed the use of their glossary of terms for inclusion in this document.

http://www.morpac.com/switches/definitions.shtml

ANSI/IEEE C37.30-1997Standard Requirements for High Voltage SwitchesCopyright 1998 by the Institute of Electrical and Electronics Engineers, Inc.345 East 47 th Street, New York, NY 10017-2394, USAISBN 1-55937-964-2

ANSI C37.32-2002High Voltage Switches, Bus Supports and AccessoriesSchedules of Preferred Ratings, Construction Guidelines and SpecificationsCopyright 2002 by the National Electrical Manufacturers Association1300 North 17 th Street, Rosslyn, VA 22209

IEEE C37.34-1994Standard Test Code for High-Voltage Air SwitchesCopyright 1995 by the Institute of Electrical and Electronics Engineers, Inc.345 East 47 th Street, New York, NY 10017-2394, USAISBN 1-55937-468-3

IEEE C37.35-1995Guide for the Application, Installation, Operation, and maintenance of High-Voltage Air Disconnecting and Interrupter SwitchesCopyright 1995 by the Institute of Electrical and Electronics Engineers, Inc.345 East 47 th Street, New York, NY 10017-2394, USAISBN 1-55937-597-3

NEMA SG 6

59269522 module 5 mv switch testing

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