drawing reading

Reading of Schematic Drawings Standard Equipment Numbers Used in Schematic Drawings 2 Time delay relay. 3 Checking or Interlocking relay. 4 Master contactor. 8 Control power disconnecting switch, e.g. MCB (8A) 21 Distance Protection relay. 25 Synchronizing or Check synchronizing relay. 27 Under voltage relay. 29 Isolator / Disconnector. 30 Annunciator relay. 32 Directional power relay. 37 Under power relay. 40 Field failure relay. 43 Auto reclose relay / Remote – Local switch in circuit breaker. 46 Reverse phase or phase balance relay. 47 Phase sequence voltage relay. 49 Thermal relay. 50 Instantaneous Overcurrent & Earth fault relay. 51 IDMTL Overcurrent & Earth fault relay. 52 A.C. Circuit breaker. 52a Circuit Breaker auxiliary switches normally open. 52b Circuit Breaker auxiliary switches normally close. 55 Power factor relay. 56 Field application relay. 59 Over voltage relay.

62 Time delay on operating relay e.g. PDR. 63 Liquid or gas pressure relay e.g. 63AR, 63GA. 64 Instantaneous Earth fault relay. 67 IDMTL Directional over current & E/F relay. 68 Blocking relay. 74 Alarm relay. 75 P.T. Selection relay / Position changing mechanism. 76 D.C. Over current relay. 77 Phase angle out of step relay 79 Reclosing relay. 80 D.C. Supervision relay e.g. 80B1, 80B2 etc. 81 Frequency relay. 83 Automatic selective control or transfer relay. 85 Carrier or pilot wire receive relay. 86 Master Trip & lockout relay. 87 Differential relay. 88 Auxiliary motor or Generator e.g. Compressor. 89 Motorized Isolator. 95 Trip circuit supervision relay. 96 Bus Bar trip relay. 97 Fuse fail relay.

SYMBOLS DESCRIPTION SYMBOLS DESCRIPTION

MAKE CONTACT MAKE CONTACT THYRISTOR

MAKE CONTACT DELAYED PICKUP

BREAK CONTACT

MAKE CONTACT DELAYED DROP OFF

BREAK CONTACT DELAYED PICKUP

MAKE CONTACT WITH BLOWN OUT MAGNET

BREAK CONTACT DELAYED DROP OFF

MAKE CONTACT HAND RESET

BREAK CONTACT WITH BLOWN OUT MAGNET


BREAK CONTACT HAND RESET

CONTROL SWITCH

CAHNGE OVER CONTACT DELAYED PICKUP

RELAY COIL GENERAL SYMBOL

CHANGE OVER CONTACT

RELAY COIL SLOW RELEASING

CHANGE OVER CONTACT HAND RESEST

RELAY COIL SLOW OPERATING

CHANGE OVER CONTACT DELAYED DROP OFF

FLAG INDICATOR


TB FOR GIS ( Global Information System).

DISC TYPE TB-CP

TB FOR DC DIST BOX/PLCC EQPT

NON DISC TYPE TB RP

TB AT CUSTOMER MARSHALLING KIOSK

DISC TYPE TB-RP

CT/VT TERMINAL BLOCK

BUSWIRE BOARD BB-CP

NON DISC TYPE TB-CP BUSWIRE BOARD BB-RP


CUB ILLUMINATION LAMP WITH D/S

FUSE

HEATER LINK

HEATER SWITCH TEST BLOCK-MPG

POWER SOCKET RESISTOR

THERMOSTAT STABILIZING RESISTOR


METROSIL SURGE DIVERTOR

ELECTRIC HOOTER/BUZZER

CONTROL/SELECTOR/DISCREPANCY SWITCH

DISCREPANCY CONTROL SWITCH (IN GA DRG)

INDICATING LAMP NO CONTACT

SEMAPHORE INDICATOR

NC CONTACT

ELECTRIC BELL PUSH BUTTON

Standard Ferrule numbers used in schematic drawings. •Symbol ‘A’ is used in C.T. ckt for main protections such as distance protection or

differential protection ckt. REF protection E.g. A-11, A-31, A-51, A-71, A-111, A-131, A-151, A-

171 etc.

•Symbol ‘B’ is used in C.T. ckt for bus bar protection E.g. B-11, B-31, B-51, B-71 etc.

•Symbols ‘C’ is used in C.T. ckt for back up directional or non directional protections

ckts.eg. - C-11, C-31, C-51, C-71, C-111, C-131, C-151, C-171 etc.

• Symbols ‘D’ is used in C.T. ckt for metering ckts.eg. D-11, D-31, D-51, D-10, D-30, D-50, D-

13, D-33, D-53 etc.

• Symbol ‘E’ is used in P.T. ckt for metering as well as protection ckt.eg. E-10, E-30, E-50, E-

110, E-130, E-150, E-11, E-31, E-51, E-111, E-131, E-151 etc.

•Symbol ‘H’ is used for A.C. ckt, as heater ckt, Panel-lightning ckt, socket ckt. e.g. H1, H2,

H3, H4, etc.

•Symbol ‘J’ is used for D.C. ckt, in coming supply of D.C. e.g. J1, J2, J3, J4 etc. (Before

fuse).

•Symbol ‘K’ is used for D.C. ckt, control supply after fuse e.g. K1, K2, K101, K102 etc.

•Symbol ‘L’ is used for indication ckt whether A.C. / D.C. e.g. L1, L2, & annunciation ckt e.g.

L101, L102, etc.

•Symbol ‘M’ is used for spring charge motor ckt, whether A.C. or D.C. e.g. M1, M2, M3, M4

etc.

•Symbol ‘N’ is used for OLTC control ckt, e.g. N8, N23 etc.

•Symbol ‘P’ is used for D.C. ckt in bus bar protection panel. eg.P1, P3, P5, P7 etc.

•Symbol ‘S’ is used in C.T. ckt for C.T. secondary wiring from C.T. secondary box to C.T.

Marshalling box e.g. R-1S1, R-1S2, Y-2S2, B-3S1 etc.

•Symbol ‘T’ is sometimes used for trip ckt e.g. K-3AT, K-3BT, etc.

•Symbol ‘U’ is used for equipment spare auxiliary contacts e.g. U1, U2, U11, U12 etc.

• Symbol ‘R-Y-B’ are used for phases & phase sequence in C.T. ckt, P.T. ckt as well as A.C.

ckt.

Purpose of Auxiliary Contacts:- The Auxiliary contacts are used for following purposes:- •Auxiliary contacts are the replica of main contacts. •To use breaker contacts for various purposes, Auxiliary contacts are used. •Auxiliary contacts are used for indication purposes. •Auxiliary contacts are used for protection of CC & TC. •Sometimes Auxiliary contacts are used for alarm. •Auxiliary contacts are used for PDR Circuit. •Auxiliary contacts are used for TCS Circuit. •Auxiliary contacts are used for various interlocks.

Multiplication of Auxiliary contacts:- •In some equipment, only one or two Auxiliary contacts remain available but in scheme, we require more contacts. So, to get more contacts, we multiply one contact by using Auxiliary relay. •Sometimes we require a number of contacts of one equipment as interlocks in C & R panel. It is not economical to bring a number of contacts through cables. So we multiply only one contact in C & R panel by using Auxiliary relay. •By using contact multiplication method, the problem of voltage drop from control room to switch yard and from switch yard to control room, can be avoided.

drawing reading

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