NAME

STUDENT I.D

ETEC 4931 Electricity Systems

Electrical Symbols and Terminology

Standard Drawing SymbolsWhen we produce a drawing of an electrical circuit, layout, or arrangement we assume that the intended recipient will be able to understand what we have produced. In the case of drawings for contractors or sub contractors to use for construction or installation purposes, they not only have to understand the drawing, but must be able to use it to produce an accurately completed job.

Many companies over the years have developed their own particular drawing styles, and in some cases their own particular symbols to represent contacts, relays, locations etc. Where these are used “in house” ie by their own staff, who know and understand the symbols used, this is fine and doesn’t create any problems. When these same drawings are sent to outside companies and individuals, the problems start to arise.

In some instances the drawings will be well documented and the symbols used identifiable or identified in an accompanying legend. No problem, the drawings can be used. However additional time will be required to ensure accuracy, and if the drawings are to be updated and kept as “As Built” they may need to be re-drawn to match the recipient’s site standards.

As you can imagine if everyone used his or her own individual system, that chaos would soon be the result.

To avoid this, there are national and international standards set up for drawing symbols and arrangements. For many years New Zealand adopted the British standard, and more recently with the advent of the CER agreement formed a joint Australian New Zealand standard, AS/NZS 1102, based on the international IEC 617 standard.

The joint AS/NZS 1102 standard adopts the IEC 617 standard and adds additional local symbols (designated with an A in the standard) where the item in question was missing from the IEC list of symbols.

Whenever you draw an electrical diagram you should use these standard symbols so all recipients can immediately follow your drawings.

NO CONFUSION!

Site PlansWhen someone decides to build a house they will normally employ an architect to design the building for him or her. The architect will produce a set of drawings that show the outline and constructional details of the building. He will also normally produce site plans that the builder will use to locate the building on its site. Often the architect will also produce the location diagrams for electrical as well as other services. The clever electrician will obtain a set of these to work with in pricing the job, working out the mains cable routes etc. prior to applying for supply etc.

Site plans can be simple sketches or detailed cad drawings. The net result is the same. They should identify the location of the site, Show outlines of all buildings and other major features and show measurement detail. A simple example follows.

This example site plan drawing, is taken from AutoCad LT, the plan shows a site with a building, paths and car parking. This particular drawing is using imperial measurements but metric measurements would be more appropriate in New Zealand.

With any site plan it is easy to add the mains cable route, the location of the meter box, the location of the pillar box from which the supply is obtained and the sizes of the cables etc.

Location diagrams

When we consider our site plan, (above) we can see enough detail to install our mains cable, earthing, our meter box and main switch board. When we come to wire the house or flat, we need more detail. This is where the location diagram comes in. Once again the architect will usually draw an electrical location diagram as a part of the overall set of plans for the construction, and all we need do is follow these. If they don’t exist you can get a copy of the builder’s plans and add your electrical location information to a floor plan.

The following drawing is taken from “Electrotechnology – Principles and Practice”.

Single line - power distribution diagramsPower supply companies and those working with commercial or industrial installations generally use these diagrams.

This particular drawing is of the 11kV distribution at an industrial site. It shows 2 incoming 11kV feeders from a local sub station as well as a co-generation plant feeding a split-able 11kv main switchboard complete with metering.

This Section of the diagram shows the Sub-Station main 11kV switchboard, the 33kV feed to this board and the circuit breakers on this switchboard.CB4 shows additional protection relays. The line down from CB4 also shows the boundary between the power company and the site. Beyond this the VT’s & CT’s for the site protection relays are shown along with the protection relay circuits.

The other feeder at the left of this section also has the protection circuit displayed in the overall drawing.

This section of the diagram shows a part of the site ring-main.RMU5 (ring main unit 5) shows 2 isolators coming in and leaving the RMU. On the other side of the Bus you can see three 80A fuse switches feeding transformers. The 400V side of each transformer feeds another Bus for 400Volt distribution further down.

Note the Bus coupler between the sections of the main distribution for the two boilers, along with the two transformers being fed from different RMU’s you have several options for a more secure source of supply.

These drawings are obviously from a real site situation and are incomplete. However there is enough information in them to show you what the “Single line” diagram represents. Each line actually covers three phases Neutral & Earth’s as appropriate.

Common Symbols

AS/NZS 1102 general symbolsCommonly accepted symbol for direct current (d.c.) - not the only symbol.

Commonly accepted symbol for alternating current (a.c.).Suitable for use with either alternating or direct current.

Positive polarity.

Negative polarity.

N Neutral

Material, unspecified

Material, solid

Material, liquid

Material, gas

Material, electret - (permanently polarised dielectric - analogues to a permanent magnet), used in microphones.Material, semiconducting

Material, insulating (dielectric)

Thermal operation

Electromagnetic operation

Radiation, non-ionising, electromagnetic (for example, radio waves or visible light)Radiation, ionising (X=X-ray, g=Gamma ray)

Earth, general symbolGround, general symbol

Protective earthProtective ground

FrameChassis

FaultIndication of assumed fault location

Moving (for example sliding) contact

Conductors and Connecting Devices - 617.3 (AS 1102.103)

Conductor, or group of conductors, or line, or cable, or circuit

Three conductors

3 Three conductors

500V

2 70mm Al 2

EXAMPLE: Direct current circuit, 500V, two 70mm2 Aluminium conductors.

3N 50 Hz 400V

3 x 6 + 1 x 4

EXAMPLE: 3-Phase circuit, 50Hz, 400V, three conductors of 6.0mm2, with a neutral of 4.0mm2.

Flexible conductor

Screened conductor

n n conductors within one screen

Two twisted conductors

Three conductors in a cable

Conductor or cable not connected

Conductor or cable not connected and specially insulated

Connection of conductors

Terminal (NOTE: The circle may be filled in)

1 2 3 4 5 6

Terminal strip (numbered)

Socket (female) - pole of a socket

Plug (male) - pole of a plug

Plug and socket (male and female)

4 Multipole plug and socket with 4 poles

Junction of conductors

Double junction of conductors

Crossing conductors not connected (NOTE: No join)

Connecting link, closed

Connecting link open

Passive Components - 617.4 (AS 1102.104)

Resistor, general symbol

Variable resistor (adjustable resistor)

U

Varistor (voltage dependant resistor)

Resistor with sliding contact

Potentiometer with sliding contact

Potentiometer, preset

Resistor with fixed tapping (1 shown)

Heating element

Capacitor, general symbol

Polarised capacitor, for example, electrolytic

Variable capacitor, adjustable capacitor

Capacitor with preset adjustment

Inductor, Coil, Choke, Winding

Inductor with magnetic core

Inductor with fixed tappings (two shown)

Piezoelectric crystal with two electrodes

Semiconductors and Electron Tubes - 617. 5 (AS 1102.105)

Semiconductor diode, general symbol

Light emitting diode, general symbol

Voltage regulator diode (Zener diode)

Bidirectional diode - Diac - conducts in both directions and used for its pulse quality at switch-on

Triode Thyristor - (triode simply means three terminal) – this symbol does not specify the gateThyristor (triode) - P-Gate (SCR)

Bidirectional triode Thyristor - Triac (can control the ac power available to the load).

PNP Transistor

NPN Transistor

Light dependant resistor

Photodiode

Phototransistor, PNP type shown

Optical coupling device (optocoupler)

XHall generator with four ohmic connections

NOTE: THIS PART OF THIS MANUAL DOES NOT INCLUDE THE ENTIRE AS 1102.105, JUST SELECTIONS FROM THAT STANDARD - WE HAVE NOT INCLUDED ANY ELECTRON TUBES HERE.

Production and Conversion of Electrical Energy - 617. 6 (AS 1102.106)

Three-phase winding, Delta

Three-phase winding, Star

Brush (on slip-ring or commutator)

*This is the general symbol for a machine. The * must be replaced with an appropriate letter: "G"-generator, "M"-motor, "MS"-synchronous motor etc.

M

Motor

M

Linear motor

M

Stepping motor

M

d.c. two-wire series motor

M

d.c. two-wire shunt motor

M1

a.c. series motor, single phase

M3

Induction motor, three-phase, squirrel cage

MInduction motor, three-phase, squirrel cage - Delta connected

M3

Induction motor, three-phase, with cage rotor, both leads of each phase brought out (squirrel cage motor)

M3

Induction motor, three-phase, with wound rotor

Transformer with two windings - two different methods of illustrating the same thing. The symbol on the left is more commonly used in single line diagrams (ie., power transformers where there would be three-phases represented as one line).The dots on this transformer indicate the instantaneous voltage polarities - Instantaneous currents entering the marked ends of the windings produce aiding fluxes.Autotransformer - two different methods of illustrating the same thing.

Current transformer - two different methods of illustrating the same thing.

Adjustable transformer, general symbol

Transformer with centre tapping on one winding

Three-phase transformer, connection star-delta

d.c. converter (switch-mode power supply)

Rectifier

Rectifier in full-wave (bridge) connection

Inverter

Primary cell - NOTE: The longer line represents the positive terminal

Battery of primary cells

The number of cells can be indicated as a number

Switchgear, Controlgear and Protective Devices 617. 7 (AS 1102.107)

Make contact (normally open) - this symbol is also used as the general symbol for a switch

The same as the symbol above only the small circle (which can be open or filled) represents a hinge-point

Break contact (normally closed)

Change-over break before make contact

Two-way contact with centre-off position

Make contact delayed when closing (operating device actuated), two shown.

Break contact delayed when re-closing (operating device released), the two shown correspond with those vertically above.

Make contact with spring return

Break contact with spring return

Manually operated switch, general symbol

Push-button switch (non-locking)

Pull-switch (non-locking)

Position switch (limit switch), make contact

Position switch (limit switch), break contact

t

Temperature sensitive switch, make contact (NOTE: t° may be replaced by operating temperature conditions.

t

Temperature sensitive switch, break contact

Self-operating thermal switch, break contact

A contact of a thermal relay, break contact

Gas discharge tube with thermal element - starter for fluorescent lamp (NOTE: the black dot represents gas)

Push-button function - may include letters (eg., ST-start, SP-stop, R-raise, L-lower, FWD-forward, REV-reverse, O-off, UP-up, DN-down, JU-jog up, JD-jog down; example ST/SP denotes stop/start button.Emergency stop function

Signal lamp function - the push button letter codes can be added to the symbol to indicate the function.

n

Speed control function

Contact on contactor (contact open in the un operated position)

Contact on contactor (contact closed in unoperated position)

Contact on contactor with automatic release

Circuit breaker

Earth-leakage circuit breaker (ELCB) also known as a Residual Current Device (RCD), general symbolMiniature overcurrent circuit breaker with thermal and electromagnetic tripping.

Disconnector - Isolator

Fuse, general symbol

Fuse-switch

Fuse-disconnector (fuse isolator)

Measuring Instruments, Lamps and Signaling Devices 617. 8 (AS 1102.108)

VVoltmeter

AAmmeter

Ohmmeter

Galvanometer

WWattmeter (Dynamometer, Power meter)

Wh

Watt-hour meter

Thermocouple, shown with polarity symbols

Clock with switch

Signal lamp, flashing type

Discharge lamp - gas filled, general symbol

Horn

Bell

Siren

Buzzer

Symbols for Location Diagrams 617. 11 (AS 1102.8)

Wiring, line or cable

Link between a switch and its associated remote socket-outlet or equipment

Junction box involving a cable joint

Mains connection box at point of attachment of the incoming supply service mains, mains entry box.

Switchboard, distribution board, frame, panel, or cubicle

Switch, general symbol

One-way switches, single-pole, two-pole and three-poleSingle-pole pull switch

Multi-position switch for different degrees of lightingTwo-way switch, single pole

Intermediate switch

Dimmer switch

tPeriod-limiting switch

Push-button switch

Push-button switch with integral indicator lampSocket-outlet - NOTE: In New Zealand practice, this symbol represents a single-phase general purpose outlet, switched and earthed.

n Multiple socket-outlet, e.g. for n plugs

Switched-outlet - This symbol may some times be more appropriate

n Multi-phase socket-outlet

Socket-outlet with isolating transformer, e.g. a shaver outlet

Electric water heater

Electric fan - NOTE: This symbol may be further qualified by the use of abbreviations (e.g. EF - Exhaust Fan)Lighting outlet position, e.g. batten holder

Lighting outlet on wall

Luminaire, or signal lamp

Luminaire fixed to wall

Luminaire on mounting bracket for pole or wall

Luminaire with built-in switch

Luminaire with reflector

Industrial type luminaire, e.g. highbay

Emergency lighting luminaire, e.g. standby or escape lighting

Fluorescent luminaire - NOTE: It is normal practice to draw the length of fluorescent luminaires to scale.

3

Fluorescent luminaire with three lamps (two examples)

Fluorescent luminaire, outdoor type - NOTE: The number of lamps and rating may be added.

Fluorescent luminare, outdoor type, with mounting bracket

Electrical appliance, general symbol. Appliance type may be described by abbreviation (e.g. HD - Hand Drier)

Unequipped wall-telephone outlet

Equipped wall-telephone outlet (with standard service installed unless otherwise qualified)

Control units for Intruder alarm equipment (two shown).