Westinghouse Electric Corporation Technical Data Relay and Telecommunications Division 41-060 Coral Springs, FL 33065 Page 1 com April, 1987 Selections from ANSI C37.2-1970 Supersedes 41-060 T WE A IEEE Device Numbers pages 1-8, dated February 4, 1975 . E, D, C/41-000A and Functions For Switchgear Apparatus

The devices 1n switching equipments are re- Device Definition Device Definition ferred to by numbers, with appropriate suff1x Number and Function Number and Function letters when necessary, according to the 5 Stopping device is a control de- 13 Synchronous-speed device, such functions they perform vice used primarily to shut down an as a centrifugal-speed switch, a equipment and hold it out of opera- slip-frequency relay, a voltage These numbers are based on a system tion. [This device may be manually relay, an undercurrent relay or any adopted as standard for automatic switchgear or electrically actuated, but ex- type of device, operates at approx- by IEEE, and incorporated in American Stand- eludes the function of electrical imately synchronous speed of a ard C37.2-1970. This system is used in con- lockout (see device function 86) on machine. nection diagrams, in instruction books, and in abnormal conditions.] specifications 14 Under-speed device functions 6 Starting circuit breaker is a when the speed of a machine falls Definition Device device whose principal function is below a predetermined value. Number and Function ------to connect a machine to its source 1 Master Element is the initiating of starting voltage. 15 Speed or frequency, matching device, such as a control switch, device functions to match and voltage relay, float switch, etc., 7 Anode circuit breaker is one used hold the speed or the frequency of which serves either directly, or in the anode circuits of a power a machine or of a system equal to, through such permissive devices as for the primary purpose of or approximately equal to, that of protective and time-delay relays to interrupting the rectifier circuit if an another machine, source or system. place an equipment in or out of arc back should occur. operation 16 Reserved for future application. 8 Control power disconnecting 2 Time-delay starting, or closing device is a disconnective device- 17 Shunting or discharge switch relay is a device which functions to such as a knife switch, circuit serves to open or to close a sh�mt- give a desired amount of time breaker or pullout fuse block, used ing circuit around any piece of delay before or after any point of for the purpose of connecting and apparatus (except a resistor), such operation in a switching sequence disconnecting the source of control as a machine field, a machine arm- or protective relay system, except power to and from the control bus ature, a capacitor or a reactor. as specifically provided by device or equipment. functions 48, 62, and 79 described Note. This excludes dev1ces wh1ch perform such shuntmg operat1ons as may be neces- later. Note· Control power 15 cons1dered to 1n- elude aux1l1ary power wh1ch suppl1es such sary in the process of startmg a mach1ne by apparatus as small motors and heaters dev1ces 6 or 42, or the1r equivalent. and 3 Checking or interlocking relay also excludes dev1ce 73 function wh1ch is a device which operates in re- serves for the switch1ng of resistors 9 Reversing device is used for the sponse to the position of a number purpose of reversing a machine of other devices, (or to a number of 18 Accelerating or decelerating de- field or for performing any other predetermined conditions), in an vice is used to close or to ca,Jse the reversing functions. equipment to allow an operating closing of circuits which are used sequence to proceed, to stop, or to increase or to decrease the speed 10 Unit sequence switch is used to to provide a check of the position of a machine. change the sequence in which units of these devices or of these con- may be placed in and out of service ditions for any purpose. Starting-to-running transition in multiple-unit equipments. 19 contactor is a device which oper- Master contactor is a device, ates to initiate or cause the auto- 4 11 Reserved for future application. generally controlledElectricalPartManuals by device matic transfer of a machine from No. 1 or equivalent and the required the starting to the running power 12 Over-speed device is usually a permissive and protective devices, connection. direct-connected speed switch that serve. to make and break the which functions on machine over- necessary control circuits to place Electrically operated valve is an speed. 20 an equipment into operation under electrically operated, controlled or the desired conditions and to take monitored valve in a fluid line. it out of operation under other or abnormal conditions. Note The funct1on of the valve may be 1/ld1cated by the use of the suff1xes. see Page 5 www Technical Data 41-060

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Device Definition Device Definition Device Definition com Number and Function Number and Function Number and Function 21 Distance relay is a device which 30 Annunciator relay is a nonauto� 39 Mechanical condition. monitor functions when the circuit admit� matically reset device that gives is a device that functions upon the tance, impedance or reactance a number of separate visual indi� occurrence of an abnormal me� increases or decreases beyond pre� cations upon the functioning of chanical condition (except that determined limits. protective devices, and which may associated with bearings as covered also be arranged to perform a under device function 38), such as 22 Equalizer circuit breaker is a lockout function excessive vibration, eccentricity, breaker which serves to control or expansion, shock. tilting, or seal to make and break the equalizer or 31 Separate excitation device con� failure. the current�balancing connections nects a circuit such as the shunt for a machine field, or for regu� field of a synchronous converter, 40 Field relay functions on a given or lating equipment in a multiple� to a source of separate excitation abnormally low value or failure of unit installation during the starting sequence; or machine field current or on an one which energizes the excitation excessive value of the reactive 23 Temperature control device and ignition circuits of a power component of armature current in functions to raise or to lower the rectifier. an ac machine indicating abnor� temperature of a machine or other mally low field excitation. apparatus, or of any medium, when 32 Directional power relay is one its temperature falls below, or rises which functions on a desired value 41 Field circuit breaker is a device above, a predetermined value. of power flow in a given direction, which functions to apply, or to or upon reverse power resulting remove, the field excitation of a Note An example IS a thermostat which from arc back in the anode or machine. switches on a space heater 1n a switchgear cathode circuits of a power rectifier assembly when the temperature falls to a des1red value as distinguished from a de- 42 Running circuit breaker is a vice which 15 used to prov1de automatiC 33 Position switch makes or breaks device whose principal function is temperature regulation between close contact when the main device or to connect a machine to its source lim1ts and would be des1gnated as 90T piece of apparatus, which has no of running or operating voltage. � device function number, reaches a This function may also be used for a 24 $Volts per hertz relay is a relay given position. device, such as a contactor. that is that functions when the ratio of used in series with a circuit breaker voltage to frequency exceeds a 34 Master sequence device is a or other fault protecting means, pre-set value. The relay may have device such as a motor�operated primarily for frequent opening and an instantaneous or inverse time multi�contact switch, or the equiv� closing of the circuit. characteristic. alent, or a programming device, such as a computer, that establishes 43 Manual transfer or selector 25 Synchronizing or synchronism- or determines the operating se- device transfers the control cir- check device operates when two quence of the major devices in an cuits so as to modify the plan of ac circuits are within the desired equipment during starting and operation of the switching equip� limits of frequency, phase angle or stopping or during other sequential ment or of some of the devices. voltage, to permit or to cause the switching operations. paralleling of these two circuits. 44 Unit sequence starting relay is a 35 Brush-operating, or slip-ring- device which functions to start the 26 Apparatus thermal device short-circuiting, device is used next available unit in a multiple� functions when the temperature of for raising, lowering, or shifting unit equipment on the failure or on the shunt field or the armortisseur the brushes of a machine, or for the non�availability of the normally winding of a machine, or that of a short�circuiting its slip rings, or for preceding unit. load limiting or load shifting resistor engaging or disengaging the con� or of a liquid or other medium ex� tacts of a mechanical rectifier. 45 Atmospheric condition monitor ceeds a predetermined value; or if is a device that functions upon the the temperature of the protected 36 Polarity or polarizing voltage occurrence of an abnormal atmos� apparatus, such as a power recti� device operates or permits the pheric condition, such as damaging tier, or of any medium decreases operation of another device on a fumes, explosive mixtures, smoke, below a predetermined value. predetermined polarity only or or fire. ElectricalPartManualsverifies the presence of a polarizing 27 Undervoltage relay is a device voltage in an equipment. 46 Reverse-phase, or phase-bal- which functions on a given value ance, current relay is a relay of undervoltage. . 37 Undercurrent or underpower which functions when the poly� relay functions when the current phase currents are of reverse�phase 28 Flame detector is a device that or power flow decreases below a sequence, or when the polyphase monitors the presence of the pilot predetermined value. currents are unbalanced or contain or main flame in such apparatus as negative phase�sequence compo� � a gas turbine or a steam boiler. 38 Bearing protective device tunc� nents above a given amount. tions on excessive bearing tempera� 29 Isolating contactor is used ex� ture, or on other abnormal mechan� 47 Phase-sequence voltage relay pressly for disconnecting one cir� ical conditions, such as undue wear, functions upon a predetermined cuit from another for the purposes which may eventually result in value of polyphase voltage in the of emergency operation, mainte� excessive bearing temperature. desired phase sequence. nance, or test. www (8 Added since previous issue. 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Device Definition Device Definition Device Definition com Number and Function Number and Function Number and Function 48 Incomplete sequence relay is a 57 Short-circuiting or grounding 66 Notching or jogging. device relay that generally returns the device is a primary circuit switch- functions to allow only a specified equipment to the normal, or off, ing device that functions to short- number of operations of a given de- position and locks it out if the nor- circuit or to ground a circuit in vice, or equipment, or a specified mal starting, operating or stopping response to automatic or manual number of successive operations sequence is not properly completed means. within a given time of each other within a predetermined time. If the It also functions to energize a device is used for alarm purposes 58 Rectification failure relay is a circuit periodically or for fractions only, it should preferably be desig- device that functions if one or more of specified time intervals, or that is nated as 48A (alarm) anodes of a power rectifier fail to used to permit intermittent accel- fire. or to detect an arc-back or on eration or jogging of a machine at 49 Machine, or transformer, ther- failure of a to conduct or low speeds for mechanical posi- mal relay is a relay that functions block properly. tioning. when the temperature of a machine armature, or other load carrying 59 Overvoltage relay is a relay that 67 Ac directional overcurrent relay winding or element of a machine, functions on a given value of is a relay that functions on a de- or the temperature of a power recti- overvoltage. sired value of ac overcurrent flow- fier or power transformer (includ- ing in a predetermined direction. ing a power rectifier transformer) 60 Voltage or Current balance relay exceeds a predetermined value. is a relay that operates on a given 68 Blocking relay is a relay that difference in voltage, or current initiates a pilot signal for blocking 50 Instantaneous overcurrent, or input or output of two circuits. of tripping on external faults in a rate-of-rise relay is a relay that transmission line or in other appa- functions instantaneously on an 61 Reserved for future application. ratus under predetermined condi- excessive value of current, or on tions. or cooper�tes with other an excessive rate of current rise. 62 Time-delay stopping or opening devices to block tripping or to thus indicating a fault in the ap- relay is a time-delay relay that block reclosing on an out-of-step paratus of circuit being protected. serves in conjunction with the condition or on power swings. device that initiates the shutdown, 51 Ac time overcurrent relay is a stopping. or opening operation in 69 Permissive control device is relay with either a definite or in- an automatic sequence. generally a two-position, manually verse time characteristic that func- operated switch that in one position lions when the current in an ac 63 Pressure switch is a switch which permits the closing of a circuit circuit exceeds a predetermined operates on given values or on a breaker, or the placing of an equip- value. given rate of change of pressure. ment into operation, and in the other position prevents the circuit 52 Ac circuit breaker is a device that 64 Ground protective relay is a breaker or the equipment from is used to close and interrupt an ac relay that functions on failure of being operated. power circuit under normal condi- the insulation of a machine, trans- tions or to interrupt this circuit former or of other apparatus to 70 Rheostat is a variable resistance under fault or emergency con- ground, or on flashover of a de device used in an electric circuit. ditions. machine to ground. which is electrically operated or has other electrical accessories, 53 Exciter or de generator relay Note T hrs functron is assrgned only to a such as auxiliary, position, or limit is a relay that forces the de ma- relay whrch detects the flow of current switches. from the frame of a machine or enclosrng chine field excitation to build up case or structure of a prece of apparatus to during starting or which functions ground. or detects a ground on a normally 71 Level switch is a switch which when the machine voltage has built ungrounded wrndmg or crrcurt It is not operates on given values, or on a applred to a devrce connected m the sec· up to a given value. given rate of change, of level. ondary crrcurt or secondary neutral of a current transformer, or 111 the secondary 54 Reserved for future application neutral of current transformers, connected 72 De circuit breaker is used to rn the power crrcurt of a normally grounded close and interrupt a de power system 55 Power factor relay is a relay that circuit under normal conditions operates whenElectricalPartManuals the power factor 65 Governor is the assembly of fluid, or to interrupt this circuit under in an ac circuit rises above or electrical, or mechanical control fault or emergency conditions. below a predetermined value. equipment used for regulating the . flow of water, steam, or other 73 Load-resistor contactor is used 56 Field application relay is a relay medium to the prime mover for to shunt or insert a step of load that automatically controls the such purposes as starting, holding limiting, shifting, or indicating application of the field excitation speed or load, or stopping. resistance in a power circuit, or to to an ac motor at some predeter- switch a space heater in circuit, or mined point in the slip cycle. to switch a light, or regenerative load resistor of a power rectifier or other machine in and out of circuit. www Technical Data 41-060

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Device Definition Device Definition Device Definition com Number and Function Number and Function Number and Function 74 Alarm relay is a device other than 83 Automatic selective control or 91 Voltage directional relay. is a an annunciator, as covered under transfer relay is a relay that oper- relay that operates when the voltage device No. 30, which is used to ates to select automatically be- across an open circuit breaker or operate, or to operate in connection tween certain sources or conditions contactor exceeds a given value in with, a visual or audible alarm in an equipment, or performs a a given direction transfer operation automatically. 75 Position changing mechanism is 92 Voltage and power directional a mechanism that is used for mov- 84 Operating mechanism is the relay is a relay that permits or ing a main device from one position complete electrical mechanism or causes the connection of two cir- to another in an equipment; as for servo-mechanism, including the cuits when the voltage difference example, shifting a removable cir- operating motor, solenoids, posi- between them exceeds a given cuit breaker unit to and from the tion switches, etc , for a tap value in a predetermined direction connected, disconnected, and test changer, induction regulator or any and causes these two circuits to positions. similar piece of apparatus which be disconnected from each other has no device function number. when the power flowing between 76 De overcurrent relay is a relay them exceeds a given value in the that functions when the current in a 85 Carrier or pilot-wire receiver opposite direction. de circuit exceeds a given value. relay is a relay that is operated or restrained by a signal used in con- 93 Field changing contactor func- 77 Pulse transmitter is used to nection with carrier-current or de tions to increase or decrease in generate and transmit pulses over pilot-wire fault directional relaying. one step the value of field excita- a telemetering or pilot-wire circuit tion on a machine. to the remote indicating or receiv- 86 Locking-out relay is an electrically ing device. operated hand, or electrically, reset 94 Tripping or trip-free relay func- relay that functions to shut down tions to trip a circuit breaker, con- 78 Phase ;mgle measuring, or out- and hold an equipment out of serv- tactor, or equipment, or to permit of-step protective relay is a relay ice on the occurrence of abnormal immediate tripping by other de- � that fu net ions at a predetermined conditions. vices; or to prevent immediate phase angle between two voltages reclosure of a circuit interrupter, or between two currents or between 87 Differential protective relay is a in case it should open automatically voltage and current. protective relay that functions on even though its closing circuit is a percentage or phase angle or maintained closed. 79 Ac reclosing relay is a relay that other quantitative difference of two controls the automatic reclosing currents or of some other electrical 95 Used only for specific applications and locking out of an 3C circuit quantities. 96 on individual installations where interrupter. none of the assigned numbered 88 Auxiliary motor or motor gen- 97 functions from 1 to 94 is suitable. 80 Flow Switch is a switch which erator is one used for operating 98 operates on given values, or on a auxiliary equipment such as pumps, given rate of change, of flow. blowers, exciters, rotating mag- 99 netic amplifiers, etc. 81 Frequency relay is a relay that Supervisory Control and Indica- functions on a predetermined 89 Line switch is used as a discon- tion. A similar series of numbers, value of frequency-either under necting load-interrupter, or iso- prefixed by the letters RE (for "re- or over or on normal system fre- lating switch in an ac or de power mote") shall be used for the inter- quency -or rate of change of circuit, when this device is elec- posing relays performing functions frequency. trically operated or has electrical that are controlled directly from accessories, such as an auxiliary the supervisory system Typical ex- 82 De reclosing relay is a relay that switch, magnetic lock, etc. am pies of such device functions controls the automatic closing are RE1, RE5, and RE94. and reclosing of a de circuit inter- 90 Regulating device functions to "RE" rupter, generally in response to regulate a quantity, or quantities, Note The use of the pref1x for th1s purpose 1n place of the former 200 senes load circuit conditions. such as voltage, current, power, of numbers now makes 1t poss1ble to obta1n ElectricalPartManualsspeed, frequency, temperature, and mcreased f\ex1bil1ty of the device funct1on load, at a certain value or between numbenng system For example. 1n p1pe- l1ne pump stations, the numbers 1 through certain (generally close) limits for 99 are applied to dev1ce functions that are . machines, tie lines or other ap- assoc1aterl w1th the over-all stat1on opera- paratus. t1on A Similar ser1es of numbers. startmg with 101 1nstead of 1, are used for those devtce functions that are assoctated wtth unit 1, a Similar series start1ng w1th 201 for devtce functtons that are assocrated wrth un1t 2, and so on, for each un1t Hl these � ir1stallat1ons www Technical Data 41-060

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Devices Performing More Than The suffix letters which denote parts of the Main Devices com One Function main device, and those which cannot or need These letters denote the location of the If one device performs two relatively impor­ not form part of the device function designa­ main device in the circuit, or the type of tant functions in an equipment so that it is tion, are generally written directly below the circuit in which the device. is used or the type desirable to identify both of these functions, device function number on drawings, as for of circuit or apparatus with which it is asso­ this may be done by using a double function example, ciated, when this is necessary, such as: number and name such as: g ar � A -Alarm or Auxiliary Power 50/51 Instantaneous and Time Overcurrent CC A AN -Anode Relay. B -Battery, or Blower, or Bus Auxiliary Devices BK -Brake Suffix Numbers Separate Auxiliary Devices BL -Block (Valve) If two or more devices with the same function X BP -Bypass number and suffix letter (if used) are present Y -Auxiliary relayCD BT -Bus Tie in the same equipment, they may be distin­ z C -Capacitor. or Condenser, Compensa- guished by numbered suffixes as for example, R -Raising relay tor, or Carrier Current or Case or 52X-1 52X-2 and 52X-3, when necessary. L -Lowering relay Compressor 0 -Opening relay or contactor CA -Cathode Suffix Letters C -Closing relay or contactor CH -Check (Valve) Suffix letters are used with device function CS -Control switch D -Discharge (Valve) numbers for various purposes. In order to pre­ CL -Auxiliary Relay, open (energized when E -Exciter vent possible conflict each suffix letter should main device is in open position) F -Feeder, or Field, or Filament, or Filter, have only one meaning in an individual equip­ OP -Auxiliary Relay, Open (energized when or Fan ment. All other words should use the abbre­ main device is in open position) G -Generator, or Ground<2l viations as contained in American Standard U -"Up" position-switch relay H -Heater, or Housing Z32.13-1950, or latest revision thereof, or D -"Down" position-switch relay L -Line or Logic should use some other distinctive abbreviation, PB -Push button M -Motor, or Metering or be written out in full each time they are N -Network, or Neutral@ used The meaning of each single suffix letter, CD In the control of a CirCuit breaker w1th so-called X-Y P -Pump or Phase Comparison or combination of letters, should be clearly relay control scheme, the X relay 15 the dev1ce whose R -Reactor. or Rectifier, or Room rna1n cont(lcts are used to energ1ze the clos1ng coil or designated in the legend on the drawings or the dev1ce wh1ch 1n some other manner, such as by the S -Synchronizing or Secondary or Strainer publications applying to the equipment. release of stored energy, causes the breaker to close or Sump or Suction (Valve) In cases where the same suffix (consisting The contacts of theY relay prov1de the ant1-pump T -Transformer, or of one letter or a combination of letters) has feature for the Circuit breaker TH -Transformer (high-voltage side) different meanings in the same equipment, Actuating Quantities TL -Transformer (low-voltage side) depending upon the device function number These letters indicate the condition or elec­ TM -Telemeter with which it is used, then the complete U trical quantity to which the device responds. -Unit device function number with its suffix letter or or the medium in which it is located. such as: letters and its corresponding function name � Suff1x "N" is generally used 111 preference to " G " for m should be listed in the legend in each case, as A -Air, or Amperes or Alternating dev1ces connected the secondary neutral of current C -Current transformers, or 1n the secondary of a current trans­ follows 90V, . former whose primary wind1ng IS located 1n the neutral D -Direct or Discharge of a mach1ne or power transformer, except 1n the case of transmiSSIOn lme relay1ng. where the suffix "G " IS Lower case (small) suffix letters are used in E -Electrolyte F -Frequency, or Flow or Fault more commonly used for those relays which operate on practically all instances on electrical diagrams ground faults for the auxiliary, position. and limit switches. H -Explosive J Capital letters are generally used for all -Differential other suffix letters. L -Level, or Liquid P -Power, or Pressure The letters should generally form part of the PF -Power Factor Q -Oil device function designation, are usually writ­ ten directly after the device function number, S -Speed or Suction or Smoke -Temperature as for example, 52CS, 71W, or 49D. When it is T -Voltage, Volts, or Vacuum necessary to use two types of suffix letters in V connection with one function number, it is VAR-Reactive Power VB -Vibration often desirable for clarity to separate them by W -Water, or Watts a slanted line or dash, as for example, 20D/CS or 20D-CS ElectricalPartManuals . www Technical Data 41-060

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Main Device Parts Standard reference positions of some Other Switches com These letters denote parts of the main de­ typical devices are as follows: These letters cover all other distinguishing vice, divided in the two following categories: features or characteristics or conditions, Device Standard which serve to describe the use of. the de­ 1.) All parts, except auxiliary contacts, Reference Position vice or its contacts in the equipment such as: position switches, limit switches, and A -Accelerating, or Automatic torque limit switches. B -Blocking, or Back-up BK -Brake Power Circuit Breaker Main Contacts Open C -Close, or Cold C -Coil, or Condenser. or Capacitor Disconnecting Switch Main Contacts Open D -Decelerating, Detonate, or Down, or CC -Closing Coil Load-break Switch Main Contacts Open Disengaged HC -Holding Coil Valve Closed Position E -Emergency or Engaged M -Operating Motor Gate Closed Position F -Failure, or Forward MF -Fly-Ball Motor Clutch Disengaged Position H -Hot, or High ML -Load-limit Motor Turning Gear Disengaged Position HR -Hand Reset MS -Speed adjusting, or Synchronizing, Power Electrodes Maximum Gap Position HS -High Speed Motor Rheostat Maximum Resistance L -Left, or Local, or Low, or Lower, or S -Solenoid Position Leading Sl -Seal-in Adjusting MeansOJ Low or Down Position M -Manual TC -Trip Coil Relay0 Deenergized Position OFF -Off V -Valve Contactor0 Deenergized Position ON -On Relay (latched-in See 2-9.7.2 P -Polarizing 2.) All auxiliary contacts and position and type) R -Right, or Raise, or Reclosing, or Re- limit switches for such devices and equip­ Contactor (latched-in Main Contacts Open ceiving, or Remote, or Reverse ment as circuit breakers. contactors, valves type) S -Sending, or Swing and rheostats and contacts of relays. These Temperature Relay® Lowest Temperature T -Test, or Trip, or Trailing are designated as follows: Level Detector® Lowest Level TDC -Time-delay Closing a -Contact that is open when the main Flow Detector® Lowest Flow TOO-Time-delay Opening device is in the standard reference posi­ Speed Switch® Lowest Speed U -Up tion, commonly referred to as the non­ Vibration Detector® Minimum Vibration operated or deenergized position, and Pressure Switch® Lowest Pressure that closes when the device assumes Vacuum Switch® Lowest Pressure, i.e., the opposite position Highest Vacuum b -Contact that is closed when the main The simple designation "a" or "b" is used in illl device is in the standard reference posi­ cases where there is no need to adjust the tion, commonly referred to as the non­ contacts to change position at any particular operated or deenergized position, and point in the travel of the main device or where that opens when the device assumes the part of the travel where the contacts the opposite position change position is of no significance in the control or operating scheme. Hence the "a" aa -Contact that is open when the operating and "b" designations usually are sufficient for mechanism of the main device is in the circuit breaker auxiliary switches. nonoperated position and that closes Note If several srmilar auxiltary swrtches are present on when the operating mechanism assumes the same devrce, they should be desrgnated numencally the opposite position 1, 2, 3, etc. when necessary bb -Contact that is closed when the oper­ CD I h(:st: nl av bf: speed. ating mechanism of the main device is adJustrng dcvrccs ur- ut her conl puncnts in the nonoperated position and that Cbl These electr rc- ally are of the non opens when the operating mechanism latched-rn typP, whose contact posl!ron rs dependt=:nt assumes the opposite position only �pun the cJegr-ee of energrzatron of the lJper atrr1g or r f:?St' or holdrnq cor I or curls whrch n1ay or- r:1ay not be for contmuou:; The cJeenergrzed pusrtrcHl uf the devrce rs that all curls deencr-grzcd ® ThP mflucnces for these Uevrccs CHC cun temper-ature, r-ISing rncreasrng vrbr-atrun ElectricalPartManualsc:md rnucasrng pressuu? .

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Page 7 com Representation of Device Contacts on In the case of latched-in or hand-reset locking­ Electrical Diagrams out relays, which operate from protective On electrical diagrams the "b"contacts of all devices to perform the shutdown of an equip­ . devices, including those of relays and those ment and to hold it out of service, the contacts with suffix letters or percentage figures, should preferably be shown in the normal should be shown as closed contacts, and all nonlocking-out position. In generaL any de­ "a"contacts should be shown as open con­ vices, such as electrically-operated latched-in tacts. The use of the single letters "a"and "b" relays, which have no deenergized or non­ with the contact representation is generally operated position, and have not been specifi­ superfluous on the diagrams. However, these cally covered in the above paragraphs should letters are a convenient means of reference in have their contacts shown in the position most the text of instruction books, articles, and suitable for the ready understanding of the other publications. operation of the devices in the equipment and sufficient description should be present The opening or closing settings of the con­ as necessary, on the elementary diagram to tacts, and auxiliary, position and limit switches, indicate the contact operation.® should, when necessary for the ready under­ standing of the operation of the devices in the ® Th1s informatiOn should be included on that part of equipment be indicated on the elementary the elementary diagram, either with the dev1ce symbol or w1th the contacts 1n the circu1t diagram Itself, where diagram for each such contact In the case of most conven1ent for the ready understandmg of the relay contacts, this indication would consist operation of the dev1ces and equ1pment of the numerical settings.

For those devices that have no de-energized or nonoperated position, such as manually­ operated transfer or control switches (in­ cluding those of the spring-return type) or auxiliary position indicating contacts on the housings or enclosures of a removable circuit breaker unit the preferred method of repre­ senting these contacts is as an "a"switch Each contact should, however, be identified on the elementary diagram as to when it closes.® For example, the contacts of the Manual-Automatic Transfer Switch, device function 43, which are closed in the automatic position, would be identified with the letter "A," and those that are closed in the manual position would be identified with the letter "M ,"and the auxiliary position switches on the housing 52H of a removable circuit break­ er unit which are closed when the unit is in the connected position, may be identified by the suffix letters "IN, "and those which are closed when the unit is withdrawn from the housing may be identified by the suffix letters "OUT."

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ElectricalPartManuals . Westinghouse Electric Corporation Relay and Telecommunications Division Coral Springs, FL 33065

www April, 1987