HANDBOOK FOR PROTECTION ENGINEERS

Handbook For Protection Engineers-Free PDF

  • Date:10 Mar 2020
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ACKNOWLEDGEMENTS, The Hand Book covers the Code of Practice in Protection Circuitry including. standard lead and device numbers mode of connections at terminal strips colour. codes in multicore cables Dos and Donts in execution Also principles of various. protective relays and schemes including special protection schemes like differential. restricted directional and distance relays are explained with sketches The norms of. protection of generators transformers lines Capacitor Banks are also given. The procedures of testing switchgear instrument transformers and relays are. explained in detail The close and trip indication and alarm circuits for variety of. Circuit breakers indicating ferrule numbers are also included All relevant. information and circuit diagrams necessary for trouble shooting are also given. We have more than 25 years experience each in protective relaying and. included a lot of information by way of original contribution apart from collection of. useful information from a large number of reference books manuals of. manufacturers etc and it is hoped that this Hand Book will serve as a useful guide. for all practicing Engineers,1 Code of Practice,1 1 Standard number for devices. 1 2 Types of Panels, 1 3 Protective Relay Connection Zones of Protection. 1 4 Norms of Protection for Generator Transformers Lines. 1 5 Current Transformers,1 6 Voltage Transformers,1 7 Energy Meters. 1 8 Synchronising Panel,2 Generator and their Protection.
3 Transformers and their Protection, 4 Distance Relays in A P System relay indications their Meanings. 5 Busbars Arrangements Protection,6 O L E F relays. 7 Circuit Breakers,8 Station Battery,9 Earthing Practices. 10 Excitation Voltage Regulation,PROTECTION, OBJECTIVE To quickly isolate a faulty section from both ends so that the rest of the. System can function satisfactorily,THE FUNCTIONAL REQUIREMENTS OF THE RELAY.
i Reliability The most important requisite of protective relay is reliability since. they supervise the circuit for a long time before a fault occurs if a. fault then occurs the relays must respond instantly and correctly. ii Selectivity The relay must be able to discriminate select between those. conditions for which prompt operation is required and those for which no. operation or time delayed operation is required, iii Sensitivity The relaying equipment must be sufficiently sensitive so that it. operates reliably when required under the actual conditions that. produces least operating tendency, iv Speed The relay must operate at the required speed It should neither be too. slow which may result in damage to the equipment nor should it be too. fast which may result in undesired operation,HEALTHY TRIP CIRCUT. High Resistance,Relay Contact,Battery Trip Coil,IMPORTANT ELEMENTS. Switch gear Circuit breaker Bulk oil Minimum oil SF6 Airblast Vacuum etc depending. on medium used for quenching the arc Different operating mechanisms such. as solenoid spring pneumatic hydraulic etc are employed. Protective gear Relays current voltage impedance power frequency etc based on. operating parameter definite time inverse time stepped etc as per. operating characteristic logic wise such as differential over fluxing etc. Station Battery A Station battery containing a number of cells accumulate energy during the. period of availability of A C supply and discharge at the time when relays. operate so that relevant circuit breaker is tripped. CODE OF PRACTICE,CODE OF PRACTICE PROTECTION,1 00 Circuitry.
1 01 The entire wiring of circuitry for indications alarms metering and protection should be. permanent wiring, 1 02 There is no place for temporary wiring or adhocism in Relay circuitry. 1 03 The leads should be identified by ferrules near terminals. 1 04 Every lead should end at a terminal point and no junctions by twisting is allowed If two. wires are to be terminated at same terminal they may be connected at two different. terminals and a loop provided, 1 05 The wiring should be by copper leads for C T secondaries for all cores i e metering as well. as protection, 1 06 The wiring should be by copper leads for PT secondaries also wherever they are intended. for protection, 1 07 The copper lead for 1 05 1 06 above should be stranded but not single lead type. 1 08 Aluminum leads can be used for indication alarms and PT secondaries for metering but. stranded wires only are to be used However where PTs are employed for commercial. metering stranded copper wires are to be used, 1 09 The terminations should be lugged by ring shape O lugs U shape lugs should be avoided.
1 10 For CT Secondary terminations two nuts with one spring washer and two flat washers to be. compulsorily used, 1 11 The terminal strips should be stud type with nuts and not screw in type. 1 12 Wherever two batteries are available the primary protection and back up protection should. be from different batteries, 1 13 Where there is only one battery at a Power Substation the primary and back up protections. should be given D C supply through two individual circuits with independent fuses run from. 1 13A When CBs have two trip coils both main protection and backup protection will energise. both the trip coils, 1 14 D C and A C supplies should not be taken through different cores of the same cable. 1 15 Independent D C cables should be run to every equipment in the yard and looping of D C. supply either in the yard or in the control room from one equipment to the other is not. 1 16 The D C yard lighting for emergency lighting should be through independent cables and not. mixed up with protection and other circuitry, 1 17 For indications alarms annunciations controls closing coil trip coil etc negative ve is. always given direct and positive ve is supplied only on commands like close trip relay. 1 18 Where D C protection supply is at 24 volts or 32 volts the battery units should be very near. the equipment and not in the control rooms, 1 19 In cases of 1 18 above each tripping units 24 volts or 32 volts battery with charger should.
not be used for more than two circuit breakers or equipment. 1 20 Standard colour codes for leads in control cable of different sizes should be as denoted on. the cover page, 1 21 The lead numbers are also standardised as follows so that any MRT Engineer can easily. identify the purpose for which the lead is connected by noting the lead number. J Series D C Incoming J1 J2 etc, K Series Control Closing Tripping etc K1 K2 K3 etc. L Series Alarms indications and L1 L2 L3 etc,annunciations. E Series Potential transformer secondaries E1 E2 E3 etc. H Series LT A C Supply H1 H2 H3 etc, A Series C T secondary for special protection A1 A2 A3 etc. B Series Bus bar protection B1 B2 B3 etc,C Series Protection Circuits C1 C2 C3 etc.
D Series Metering Circuits D1 D2 D3 etc, 1 22 CTs with 1 amp secondary rating should be used compulsorily where meters protective. devices etc are remotely situated with reference to equipment. 1 23 The CT ratios available and adopted with number of cores shall be displayed on each panel. as follows with underlined position as adopted,400 200 100 1 1 1. 1 24 Wherever CT cores are not used SHORTING LOOPS should be provided near CT secondary. terminals and not in marshaling boxes or at panels. 1 25 The Cable entries near equipment marshaling boxes and panels should be by use of. appropriate size glands, 1 26 The Wiring inside the panels should be clear and neatly fastened avoiding loose wires. 1 27 All wires not in use should not only be disconnected but removed from panels. 1 28 PT secondaries should have group MOCBs with D C alarm Fuses at different panels should. not be used, 1 29 Few cells from a battery of cells should not be used for separate low voltage D C circuits D C. D C converters only should be employed utilising full D C voltage of the entire battery as. 2 00 STANDARD LEAD NUMBERS, Certain lead numbers are standardised as follows and should be compulsorily adopted with.
ferrules at terminations of leads,J1 Positive,J2 Negative. Controls Alarms,Remote Close K15R,Remote Trip K5R,Local Close K15L. Local Trip K5L,Relay Family,Electro Magnetic Static Mechanical. Based on Characteristic Based on of logic,1 Definite time Relays 1 Differential a OT Trip. 2 Inverse time Relays with 2 Unbalance b WT Trip, definite minimum time 1 DMT 3 Neutral Displacement C Bearing Temp Trip.
3 Instantaneous Relays 4 Directional etc, 4 IDMT with inst 5 Restricted Earth Fault 2 Float Type. 5 Stepped Characteristic 6 Over Fluxing a Buchholz. 6 Programme Switches 7 Distance Schemes b OSR, 7 Voltage restraint overcurrent 8 Bus bar Protection c PRV. relay 9 Reverse Power Relays d Water level Controls. 10 Loss of excitation etc,Based on actuating,11 Negative Phase Sequence 3 Pressure Switches. Relays etc 4 Mechanical Interlocks,1 Current Relays 5 Pole discrepancy Relay. 2 Voltage Relays,3 Frequency Relays,4 Power Relays etc.
Types of Control Panels,1 Control Panels 12 Marshalling Boxes. 2 Relay Panels 13 AMG Panels,3 Control Relay Panels 14 Machine Panels. 4 Synchronising Panel or 15 Duplex HV LV Panels, 5 Communication Panels 16 Bus Zone Protection Panels. 6 Annunciation Panels 17 RTC Panels OLTC,7 D C Distribution Board 18 RTI Panels temp. 8 A C Distribution Board 19 Indoor Panels,9 Charger Panels 20 Outdoor Panels.
10 Relay Galleries 21 Panels with drawn up,11 Auxiliary Control Panels mimics isolator cum. breaker status indication,Semaphores etc,DEVICE NUMBERS AND THEIR NOMENCLATURE. 2 Time delay relay,3 Checking or Interlocking relay. 21 Distance relay,25 Check synchronizing relay,27 Undervoltage relay. 30 Annunciator relay,32 Directional power Reverse power relay.
37 Low forward power relay,40 Field failure loss of excitation relay. 46 Negative phase sequence relay,49 Machine or Transformer Thermal relay. 50 Instantaneous Overcurrent relay,51 A C IDMT Overcurrent relay. 52 Circuit breaker, 52a Circuit breaker Auxiliary switch Normally open a contact. 52b Circuit breaker Auxiliary switch Normally closed b contact. 55 Power Factor relay,56 Field Application relay,59 Overvoltage relay.
60 Voltage or current balance relay,64 Earth fault relay. 67 Directional relay,68 Locking relay,74 Alarm relay. 76 D C Overcurrent relay,78 Phase angle measuring or out of step relay. 79 AC Auto reclose relay,80 Monitoring loss of DC supply. 81 Frequency relay,81U Under frequency relay,81O Over frequency relay.
83 Automatic selective control or transfer relay,85 Carrier or pilot wire receive relay. 86 Tripping Relay,87 Differential relay,87G Generator differential relay. 87GT Overall differential relay,87U UAT differential relay. 87NT Restricted earth fault relay,95 Trip circuit supervision relay. 99 Overflux relay,186A Auto reclose lockout relay,186B Auto reclose lockout relay.
Over Current trip,E f Trip Relay trip K3 Master trip. Diffl Trip,OSR OLTC trip 163T,Bucholz trip 63T,O T trip 26T. W T trip 49T,Over fluxing trip 99,P R V trip,Ter Ala Trip 149T. Bucholz Alarm 63A,W T Alarm 49A,O T Alarm 26A,Ter Alarm 149A. Busbar prot Trip 96,Pole discrepancy trip 162,Indication ve L1.
Semaphore OFF L7,Semaphore ON L9,C B trip alarm L21. Bus A B Switch remote OFF L11,Bus indication ON L13. Line equipment OFF L15, NORMS OF PROTECTION TO BE FOLLOWED AS PER A P E R C ORDERS. For Transmission Distribution Lines,S No Voltage Protection Scheme. 1 400 KV Line Main I Non switched or Numerical Distance Scheme. Main II Non switched or Numerical Distance Scheme, 2 220 KV Line Main I Non switched distance scheme Fed from Bus PTs.
Main II Switched distance scheme Fed from line CVTs. With a changeover facility from bus PT to line CVT and vice. 3 132 KV lines Main Protection Switched distance scheme fed from bus. Backup Protection 3 Nos directional IDMT O L Relays and. 1 No directional IDMT E L relay, 4 33 KV lines Non directional IDMT 3 O L and 1 E L relays. 5 11 KV lines Non directional IDMT 2 O L and 1 E L relays. i On some of the old 220KV lines one distance scheme with backup directional IDMT 3 O L. E L relays were provided, ii On some of the 132KV grid lines only distance scheme is available. iii Very few 66KV lines are in service which are also being phased out. Busbars All 220 KV busbars will have busbar protection scheme with main and check. NORMS OF PROTECTION FOR EHV CLASS POWER TRANSFORMERS. POWER STATIONS,Voltage ratio HV Side LV Side Common relays. i 11 132 KV GT 3 Non dir O L Differential or Overall. 1 Non dir E L differential Overflux,relay and or Buchholz. standby E F OLTC Buchholz,REF PRV OT WT, ii 13 8 220 KV 3 Non dir O L Differential or Overall.
15 75 220 KV 1 Non dir E L differential Overflux,18 400 KV relay and or Buchholz. 21 400 KV standby E F OLTC Buchholz,Generator T Fs REF PRV OT WT. iii 220 6 6KV 3 Non dir O L 3 Non dir O L Differential Overflux. Station T Fs 1 Non dir E L relays Buchholz,relay and or OLTC Buchholz. standby E F PRV OT WT, iv Gen volt 6 6KV 3 Non dir O L 3 Non dir O L Differential Overflux. UAT relays relays Buchholz,OLTC Buchholz,SUBSTATIONS.
CODE OF PRACTICE CODE OF PRACTICE PROTECTION 1 00 Circuitry 1 01 The entire wiring of circuitry for indications alarms metering and protection should be permanent wiring 1 02 There is no place for temporary wiring or adhocism in Relay circuitry 1 03 The leads should be identified by ferrules near terminals

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