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SELECTION OF CIRCUIT BREAKERS
CB SWITCHING CAPABILITIES OPERATION CKT. CONDITION
MAKE
CARRY BREAK
NORMAL
OVERLOAD
SHORT-CIRCUIT
: LIMITED CAPABILITY
CB TYPES AIR CIRCUIT BREAKER (A.C.B.) MOULDED CASE CIRCUIT BREAKER (M.C.C.B.) MOTOR PROTECTIVE CIRCUIT BREAKER (M.P.C.B.) MINIATURE CIRCUIT BREAKER (M.C.B.)
ACB MAIN APPLICATION AREA AS A SWITCHING & PROTECTION DEVICE FOR POWER DISTRIBUTION (AS INCOMER, BUSCOUPLER & O/G FEEDER) - FOR TRANSFORMER PROTECTION - FOR BUSBAR/CABLE PROTECTION SWITCHING & PROTECTION OF MOTORS SWITCHING & PROTECTION OF LIGHTING LOADS SWITCHING & PROTECTION OF HEATING LOADS SWITCHING & PROTECTION OF CAPACITORS
WHY ACB ? WIDE RANGE : 400 A TO 6400 A HIGH MAKING & BREAKING CAPACITIES HIGH SHORT TIME WITHSTAND CURRENT RATING DISCRIMINATION BETWEEN VARIOUS LEVELS VARIOUS TYPES OF OVERCURRENT RELEASES
WHY ACB ? OVERCURRENT RELEASES ARE FIELD ADJUSTABLE OVER WIDE RANGE VARIOUS ACCESSORIES - U/V, SHUNT OR E/F RELEASE - LOCKS & INTERLOCKS - ELECTRICAL INDICATIONS DESIGNED FOR ACCESSIBLE MAINTENANCE & REPAIR
SELECTION OF ACB PARAMETERS TYPE RATED CURRENT, In RATED VOLTAGE, Ue RATED S/C BREAKING CAPACITY, Icu & Ics (ULTIMATE & SERVICE S/C BREAKING CAPACITY) RATED S/C MAKING CAPACITY, Icm RATED SHORT TIME WITHSTAND CURRENT, Icw UTILIZATION CATEGORY DISCRIMINATION
SELECTION OF ACB PARAMETERS TYPE OF OVERCURRENT RELEASES O/L & S/C SETTINGS ACCESSORIES - U/V, SHUNT, E/F RELEASE - LOCKS & INTERLOCKS - ELECTRICAL INDICATIONS OPERATIONAL LIFE EASE OF MAINTENANCE AVAILABILITY OF SPARES CONTROL VOLTAGE VOLUME/WEIGHT
SELECTION PARAMETERS TYPE
TYPE OF ACB
MANUALLY OPERATED
FIXED
DRAW-OUT
ELECTRICALLY OPERATED
FIXED
DRAW-OUT
SELECTION PARAMETERS ULTIMATE & SERVICE S/C BREAKING CAPACITY AS PER EARLIER IS : 2516 (NOW SUPERSEDED BY IS 13947) : P1 & P2 CATEGORIES AS PER IS 13947 PART 2 : RATED ULTIMATE S/C BREAKING CAPACITY (Icu)
& RATED SERVICE S/C BREAKING CAPACITY (Ics) Ics SHOULD BE 25% or 50% or 75% or 100% of Icu
SELECTION PARAMETERS RATED S/C MAKING CAPACITY RATIO ‘n’ BETWEEN S/C MAKING CAPACITY & S/C BREAKING CAPACITY & RELATED POWER FACTOR S/C BREAKING CAPACITY ‘I’ (KA rms) 4.5 I 6 6 I 10 10 I 20 20 I 50 50 I
POWER FACTOR
MINIMUM VALUE OF ‘n’
0.7 0.5 0.3 0.25 0.2
1.5 1.7 2.0 2.1 2.2
SELECTION PARAMETERS UTILIZATION CATEGORY TYPE APPLICATION WITH RESPECT TO SELECTIVITY
A
CBs NOT SPECIFICALLY INTENDED FOR SELECTIVITY UNDER S/C CONDITIONS WITH RESPECT TO OTHER SCPDs IN SERIES ON THE LOAD SIDE, i.e WITHOUT AN INTENTIONAL SHORT TIME DELAY PROVIDED FOR SELECTIVITY UNDER S/C CONDITIONS, & THEREFORE WITHOUT A ‘Icw’ RATING
B
CBs SPECIFICALLY INTENDED FOR SELECTIVITY UNDER S/C CONDITIONS WITH RESPECT TO OTHER SCPDs IN SERIES ON THE LOAD SIDE, i.e WITH AN INTENTIONAL SHORT TIME DELAY PROVIDED FOR SELECTIVITY UNDER S/C CONDITIONS, & THEREFORE HAVE A ‘Icw’ RATING
SELECTION PARAMETERS DISCRIMINATION WHAT IS DISCRIMINATION ? IN CASE OF FAULT IN THE SYSTEM, THE NEAREST UPSTREAM CB/FUSE SHOULD CLEAR THE FAULT
THUS ISOLATING FAULTY PART OF THE SYSTEM WHILE HEALTHY PART REMAINS UNAFFECTED
VARIOUS FAULTS FOR WHICH DISCRIMINATION IS REQUIRED • SHORT CIRCUIT
• OVERLOAD • EARTH FAULT
TYPES OF DISCRIMINATION POSSIBLE BETWEEN ACBs
TIME BASED CURRENT BASED
TIME BASED DISCRIMINATION IN CASE OF S/C FOR TIME BASED DISCRIMINATION THE FINAL ACB BEFORE THE LOAD MUST TRIP IMMEDIATELY UNDER S/C CONDITIONS (AS IT DOES NOT REQUIRE TIME DELAY) ALL UPSTREAM ACBs ARE TIME-DELAYED WITH PROGRESSIVE DELAY TIMES FOR S/C TRIPPING
CURRENT BASED DISCRIMINATION IN CASE OF S/C FOR COMPLETE CURRENT BASED DISCRIMINATION PICK-UP SETTING OF S/C PROTECTIVE RELEASE OF IMMEDIATE UPSTREAM ACB SHOULD BE > FAULT LEVEL AT THE LOCATION OF DOWNSTREAM ACB
SELECTION PARAMETERS OVERCURRENT RELEASE
THERMO MAGNETIC
ANALOG SOLID STATE
MICRO-PROCESSOR BASED
I-t CH. OF A TYPICAL THERMO-MAGNETIC RELEASE 10000 OPERATING LIMITS THERMAL
TRIP TIME IN SECONDS
1000
100 ZONE OF S / C OPERATION ( M1 / M2)
10
T. O. T. AT MAX. OF DN2 SETTING M.I.T. AT MAX. OF DN2 SETTING M.I.T. AT MIN. OF DN2 SETTING
1 0.20 0.10
DN 2 (CONT. 100 - 300 mS ) DN 1 (25 mS) TOTAL OPERATING TIME MIN. IMPULSION TIME
0.01 1
2
3 4 5 6 7 8 9 10
20
30 40 50
100
MULTIPLES OF SET CURRENT
400
1000
TRIP TIME
I-T CH. OF A TYPICAL SOLID STATE RELEASE
LONG TIME (O/L) SHORT TIME (S/C) INSTANTANEOUS (S/C) EARTH FAULT
MULTIPLES OF CURRENT
SELECTION PARAMETERS O/L & S/C SETTINGS WHAT IS PICK-UP SETTING FOR CB ?
IT IS THAT CALIBRATED VALUE OF MINIMUM CURRENT, (SUBJECT TO CERTAIN TOLERENCES) WHICH WILL CAUSE A TRIP DEVICE (e.g.OVERCURRENT RELEASE) TO ULTIMATELY TRIP THE CB IT IS NORMALLY EXPRESSED AS MULTIPLES OR PERCENTAGE OF CT TAP OR THE LONG-TIME DELAY PICK-UP
OVERLOAD SETTING PICK-UP SETTING : NO HIGHER THAN NECESSARY & WHICH MEET APPLICABLE STANDARDS WITHOUT CAUSING NUISANCE TRIPPING
TIME DELAY SETTING (WHERE APPLICABLE) : NO HIGHER THAN NECESSARY TO OVERRIDE TRANSIENT & STEADY STATE OVERCURRENTS ASSOCIATED WITH ENERGIZING OF LOAD EQUIPMENTS & TO COORDINATED WITH DOWNSTREAM PROTECTION DEVICES
SHORT CIRCUIT SETTING PICK-UP SETTING : NO HIGHER THAN NECESSARY TO AVOID NUISANCE TRIPPING & SHOULD NOT BE MORE THAN THE AVAILABLE S/C CURRENT AT LOCATION OF THE CB TIME DELAY SETTING (WHERE APPLICABLE) : THAT MINIMUM, WHICH IS REQUIRED FOR DOING TIME BASED DISCRIMINATION WITH DOWNSTREAM CBs
SELECTION PARAMETERS ACCESSORIES - U/V RELEASE • VERSIONS : 1) INSTANTANEOUS & 2) TIME DELAY • FOR - PERMITS CLOSING OF CB IF THE VOLTAGE IS 85% & TRIPS UNDER EXTREME U/V - ELECT. INTERLOCKING - REMOTE TRIPPING • OPERATION : 70% TO 35% OF Vn • PICK-UP : 85% OF Vn
SELECTION PARAMETERS ACCESSORIES - SHUNT RELEASE • VERSIONS : 1) A.C. COIL & 2) D.C. COIL
• FOR - REMOTE TRIPPING - ELECT. INTERLOCKING • OPERATION : 70% TO 110% OF Vn FOR A.C. COIL
SELECTION PARAMETERS ACCESSORIES - E/F RELEASE • VERSIONS : 1) FIXED SETTINGS OF 10%, 20% OF In & 2) FIXED SETTINGS OF 30%, 40%, 50% OF In • FOR E/F PROTECTION • ONLY IN CONJUNCTION WITH THERMOMAGNETIC RELEASE • FOR 3 PHASE 4 WIRE SYSTEM, FOURTH CT REQUIRED
SELECTION PARAMETERS ACCESSORIES - LOCKS & INTERLOCKS • LOCKABLE TRIP PUSH BUTTON (CAN ALSO BE USED FOR INTERLOCKING TWO OR MORE CBs) • ISOLATED/ANY POSITION LOCK (CAN ALSO BE USED FOR INTERLOCKING TWO OR MORE CBs) • RACKING INTERLOCK
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB • FOR - TWO I/C + ONE B/C SYSTEM - THREE I/C + TWO B/C SYSTEM • SUITABLE FOR ALL TYPES OF ACBs (MF, MDO, EF & EDO)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB TWO I/C + ONE B/C SYSTEM TRANSFORMER 1600 KVA
G
PCC
)A
21
)
22
)
13
)
11
A
12
STANDBY GENERATOR 1250 KVA
)A 23
)
24
TWO A TYPE KEYS ARE PROVIDED
)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB THREE I/C + TWO B/C SYSTEM
G
PCC
)A
21
)
22
)
23
)
14
)
11
A
STANDBY G GENERATORS
12
)A
24
)
15
)
TRANSFORMER 1600 KVA
B
13
)B
25
)
26
TWO A TYPE KEYS & ONE B TYPE KEY ARE PROVIDED
)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY ISOLATED POSITION LOCK • FOR - TWO I/C + ONE B/C SYSTEM - THREE I/C + TWO B/C SYSTEM • SUITABLE FOR ONLY DRAW-OUT ACBs (MDO & EDO)
SELECTION PARAMETERS ACCESSORIES - MICROSWITCHES FOR ELECT. INDICATIONS • SERVICE/TEST/ISOLATED POSITION INDICATION
• UNDER VOLTAGE/SHUNT/EARTH FAULT RELEASE TRIP INDICATION • O/L & S/C TRIP INDICATION - COMMON & SEPARATE
SELECTION OF ACB BASIC CRITERIA CB SHOULD HAVE ADEQUATE : • • • • •
RATED VOLTAGE, Ue RATED CURRENT, In RATED S/C BREAKING CAPACITY, Icu /Ics RATED S/C MAKING CAPACITY, Icm RATED SHORT TIME WITHSTAND CURRENT, Icw • DISCRIMINATION WITH OTHER CBs & FUSES
EXAMPLE OF ACB SELECTION SELECTION OF ACB ‘11’, ‘21’ & ‘31’ IN THE SHOWN
SINGLE LINE DIAGRAM
SINGLE LINE DIAGRAM TRANSFORMER 1600 KVA
PCC
)
22
)
)
12 13
F1
350 A
)
11 21
STANDBY GENERATOR 1250 KVA
G
F2
) 23
24
300 A
300 A
)
MCC
BUSBAR U/G CABLE
F3
)
31
)
M1
50HP
)
M2
M3
M4
100HP
30HP
150HP
CB SDF STARTER
SYSTEM DATA TRANSFORMER : 11/0.433 KV 1600 KVA
STANDBY GENERATOR : UrG = 415 V 1250 KVA INDUCTION MOTORS : M1, IrM = 70A M2, IrM = 135A M3, IrM = 40A M4, IrM = 200A
AIR CIRCUIT BREAKER ‘11’ REQUIRED CURRENT RATING TRANSFORMER FL CURRENT = 1600 × 1000 3 × 433 =
2134 A
CONSIDERING 10% OVERLOADING, TOTAL CURRENT = 1.1 × 2134 = 2347 A
In OF CB ‘11’ 2347 A
AIR CIRCUIT BREAKER ‘11’ REQUIRED S/C BREAKING CAPACITY
Icu OF CB ‘11’ IK SUPPLIED BY TRANSFORMER AT F1 38.77 KA
AIR CIRCUIT BREAKER ‘11’ REQUIRED S/C MAKING CAPACITY
Icm OF CB ‘11’ IP SUPPLIED BY TRANSFORMER AT F1 87.71 KA(PEAK)
AIR CIRCUIT BREAKER ‘21’ REQUIRED CURRENT RATING SAME AS FOR ACB ‘31’
REQUIRED S/C MAKING & BREAKING CAPACITY SAME AS FOR ACB ‘11’
AIR CIRCUIT BREAKER ‘31’ REQUIRED CURRENT RATING
In OF CB ‘31’ (IrM) (70 + 135 + 40 + 200) 445 A
AIR CIRCUIT BREAKER ‘31’ REQUIRED S/C BREAKING CAPACITY
Icu OF CB ‘31’ IK SUPPLIED BY TRANSFORMER AT F3 15.67 KA
AIR CIRCUIT BREAKER ‘31’ REQUIRED S/C MAKING CAPACITY
Icm OF CB ‘31’ IP SUPPLIED BY TRANSFORMER AT F3 27.7 KA(PEAK)
TIME BASED DISCRIMINATION SETTING OF DELAY TIMES FOR UPSTREAM ACBs MINIMUM IMPULSION TIME OF IMMEDIATE
UPSTREAM ACB SHOULD BE > TOTAL OPERATING TIME OF DOWNSTREAM ACB
TIME BASED DISCRIMINATION BETWEEN ACBs ‘11’, ‘21’ & ‘31’ SUPPOSE FOR ACB ‘31’ M.I.T. = 25 mSEC & T.O.T = 90 mSEC ACB ‘21’ ACB ‘11’
M.I.T. = 100 mSEC T.O.T. = 165 mSEC M.I.T. = 200 mSEC T.O.T = 265 mSEC
CURRENT BASED DISCRIMINATION BETWEEN ACBs ‘11’, ‘21’ & ‘31’ CURRENT BASED DISCRIMINATION IS NOT POSSIBLE BETWEEN ACB ‘11’ & ‘21’ SINCE FAULT LEVEL AT THEIR LOCATIONS ARE SAME CURRENT BASED DISCRIMINATION IS POSSIBLE BETWEEN ACB ‘21’ & ‘31’ IF S/C PICKUP SETTING OF ACB ‘21’ > IK AT F3
ACB SELECTION CHART OF VALUES OBTAINED CHARACTERISTICS
In
CB ‘11’
2347 A
CB ‘21’
445 A
CB ‘31’
445 A
Icu (RMS)
38.77 KA 38.77 KA 15.67 KA
Icm (PEAK)
87.71 KA 87.71 KA 27.7 KA
T.O.T. (mSEC) Icw
265 mSEC 165 mSEC 90 mSEC (38.77 KA FOR (38.77 KA FOR (15.67 KA FOR HT CB T.O.T.)
265 mSEC )
165 mSEC)
CB SWITCHING CAPABILITIES OPERATION CKT. CONDITION
MAKE
CARRY BREAK
NORMAL
OVERLOAD
SHORT-CIRCUIT
: LIMITED CAPABILITY
CB TYPES AIR CIRCUIT BREAKER (A.C.B.) MOULDED CASE CIRCUIT BREAKER (M.C.C.B.) MOTOR PROTECTIVE CIRCUIT BREAKER (M.P.C.B.) MINIATURE CIRCUIT BREAKER (M.C.B.)
ACB MAIN APPLICATION AREA AS A SWITCHING & PROTECTION DEVICE FOR POWER DISTRIBUTION (AS INCOMER, BUSCOUPLER & O/G FEEDER) - FOR TRANSFORMER PROTECTION - FOR BUSBAR/CABLE PROTECTION SWITCHING & PROTECTION OF MOTORS SWITCHING & PROTECTION OF LIGHTING LOADS SWITCHING & PROTECTION OF HEATING LOADS SWITCHING & PROTECTION OF CAPACITORS
WHY ACB ? WIDE RANGE : 400 A TO 6400 A HIGH MAKING & BREAKING CAPACITIES HIGH SHORT TIME WITHSTAND CURRENT RATING DISCRIMINATION BETWEEN VARIOUS LEVELS VARIOUS TYPES OF OVERCURRENT RELEASES
WHY ACB ? OVERCURRENT RELEASES ARE FIELD ADJUSTABLE OVER WIDE RANGE VARIOUS ACCESSORIES - U/V, SHUNT OR E/F RELEASE - LOCKS & INTERLOCKS - ELECTRICAL INDICATIONS DESIGNED FOR ACCESSIBLE MAINTENANCE & REPAIR
SELECTION OF ACB PARAMETERS TYPE RATED CURRENT, In RATED VOLTAGE, Ue RATED S/C BREAKING CAPACITY, Icu & Ics (ULTIMATE & SERVICE S/C BREAKING CAPACITY) RATED S/C MAKING CAPACITY, Icm RATED SHORT TIME WITHSTAND CURRENT, Icw UTILIZATION CATEGORY DISCRIMINATION
SELECTION OF ACB PARAMETERS TYPE OF OVERCURRENT RELEASES O/L & S/C SETTINGS ACCESSORIES - U/V, SHUNT, E/F RELEASE - LOCKS & INTERLOCKS - ELECTRICAL INDICATIONS OPERATIONAL LIFE EASE OF MAINTENANCE AVAILABILITY OF SPARES CONTROL VOLTAGE VOLUME/WEIGHT
SELECTION PARAMETERS TYPE
TYPE OF ACB
MANUALLY OPERATED
FIXED
DRAW-OUT
ELECTRICALLY OPERATED
FIXED
DRAW-OUT
SELECTION PARAMETERS ULTIMATE & SERVICE S/C BREAKING CAPACITY AS PER EARLIER IS : 2516 (NOW SUPERSEDED BY IS 13947) : P1 & P2 CATEGORIES AS PER IS 13947 PART 2 : RATED ULTIMATE S/C BREAKING CAPACITY (Icu)
& RATED SERVICE S/C BREAKING CAPACITY (Ics) Ics SHOULD BE 25% or 50% or 75% or 100% of Icu
SELECTION PARAMETERS RATED S/C MAKING CAPACITY RATIO ‘n’ BETWEEN S/C MAKING CAPACITY & S/C BREAKING CAPACITY & RELATED POWER FACTOR S/C BREAKING CAPACITY ‘I’ (KA rms) 4.5 I 6 6 I 10 10 I 20 20 I 50 50 I
POWER FACTOR
MINIMUM VALUE OF ‘n’
0.7 0.5 0.3 0.25 0.2
1.5 1.7 2.0 2.1 2.2
SELECTION PARAMETERS UTILIZATION CATEGORY TYPE APPLICATION WITH RESPECT TO SELECTIVITY
A
CBs NOT SPECIFICALLY INTENDED FOR SELECTIVITY UNDER S/C CONDITIONS WITH RESPECT TO OTHER SCPDs IN SERIES ON THE LOAD SIDE, i.e WITHOUT AN INTENTIONAL SHORT TIME DELAY PROVIDED FOR SELECTIVITY UNDER S/C CONDITIONS, & THEREFORE WITHOUT A ‘Icw’ RATING
B
CBs SPECIFICALLY INTENDED FOR SELECTIVITY UNDER S/C CONDITIONS WITH RESPECT TO OTHER SCPDs IN SERIES ON THE LOAD SIDE, i.e WITH AN INTENTIONAL SHORT TIME DELAY PROVIDED FOR SELECTIVITY UNDER S/C CONDITIONS, & THEREFORE HAVE A ‘Icw’ RATING
SELECTION PARAMETERS DISCRIMINATION WHAT IS DISCRIMINATION ? IN CASE OF FAULT IN THE SYSTEM, THE NEAREST UPSTREAM CB/FUSE SHOULD CLEAR THE FAULT
THUS ISOLATING FAULTY PART OF THE SYSTEM WHILE HEALTHY PART REMAINS UNAFFECTED
VARIOUS FAULTS FOR WHICH DISCRIMINATION IS REQUIRED • SHORT CIRCUIT
• OVERLOAD • EARTH FAULT
TYPES OF DISCRIMINATION POSSIBLE BETWEEN ACBs
TIME BASED CURRENT BASED
TIME BASED DISCRIMINATION IN CASE OF S/C FOR TIME BASED DISCRIMINATION THE FINAL ACB BEFORE THE LOAD MUST TRIP IMMEDIATELY UNDER S/C CONDITIONS (AS IT DOES NOT REQUIRE TIME DELAY) ALL UPSTREAM ACBs ARE TIME-DELAYED WITH PROGRESSIVE DELAY TIMES FOR S/C TRIPPING
CURRENT BASED DISCRIMINATION IN CASE OF S/C FOR COMPLETE CURRENT BASED DISCRIMINATION PICK-UP SETTING OF S/C PROTECTIVE RELEASE OF IMMEDIATE UPSTREAM ACB SHOULD BE > FAULT LEVEL AT THE LOCATION OF DOWNSTREAM ACB
SELECTION PARAMETERS OVERCURRENT RELEASE
THERMO MAGNETIC
ANALOG SOLID STATE
MICRO-PROCESSOR BASED
I-t CH. OF A TYPICAL THERMO-MAGNETIC RELEASE 10000 OPERATING LIMITS THERMAL
TRIP TIME IN SECONDS
1000
100 ZONE OF S / C OPERATION ( M1 / M2)
10
T. O. T. AT MAX. OF DN2 SETTING M.I.T. AT MAX. OF DN2 SETTING M.I.T. AT MIN. OF DN2 SETTING
1 0.20 0.10
DN 2 (CONT. 100 - 300 mS ) DN 1 (25 mS) TOTAL OPERATING TIME MIN. IMPULSION TIME
0.01 1
2
3 4 5 6 7 8 9 10
20
30 40 50
100
MULTIPLES OF SET CURRENT
400
1000
TRIP TIME
I-T CH. OF A TYPICAL SOLID STATE RELEASE
LONG TIME (O/L) SHORT TIME (S/C) INSTANTANEOUS (S/C) EARTH FAULT
MULTIPLES OF CURRENT
SELECTION PARAMETERS O/L & S/C SETTINGS WHAT IS PICK-UP SETTING FOR CB ?
IT IS THAT CALIBRATED VALUE OF MINIMUM CURRENT, (SUBJECT TO CERTAIN TOLERENCES) WHICH WILL CAUSE A TRIP DEVICE (e.g.OVERCURRENT RELEASE) TO ULTIMATELY TRIP THE CB IT IS NORMALLY EXPRESSED AS MULTIPLES OR PERCENTAGE OF CT TAP OR THE LONG-TIME DELAY PICK-UP
OVERLOAD SETTING PICK-UP SETTING : NO HIGHER THAN NECESSARY & WHICH MEET APPLICABLE STANDARDS WITHOUT CAUSING NUISANCE TRIPPING
TIME DELAY SETTING (WHERE APPLICABLE) : NO HIGHER THAN NECESSARY TO OVERRIDE TRANSIENT & STEADY STATE OVERCURRENTS ASSOCIATED WITH ENERGIZING OF LOAD EQUIPMENTS & TO COORDINATED WITH DOWNSTREAM PROTECTION DEVICES
SHORT CIRCUIT SETTING PICK-UP SETTING : NO HIGHER THAN NECESSARY TO AVOID NUISANCE TRIPPING & SHOULD NOT BE MORE THAN THE AVAILABLE S/C CURRENT AT LOCATION OF THE CB TIME DELAY SETTING (WHERE APPLICABLE) : THAT MINIMUM, WHICH IS REQUIRED FOR DOING TIME BASED DISCRIMINATION WITH DOWNSTREAM CBs
SELECTION PARAMETERS ACCESSORIES - U/V RELEASE • VERSIONS : 1) INSTANTANEOUS & 2) TIME DELAY • FOR - PERMITS CLOSING OF CB IF THE VOLTAGE IS 85% & TRIPS UNDER EXTREME U/V - ELECT. INTERLOCKING - REMOTE TRIPPING • OPERATION : 70% TO 35% OF Vn • PICK-UP : 85% OF Vn
SELECTION PARAMETERS ACCESSORIES - SHUNT RELEASE • VERSIONS : 1) A.C. COIL & 2) D.C. COIL
• FOR - REMOTE TRIPPING - ELECT. INTERLOCKING • OPERATION : 70% TO 110% OF Vn FOR A.C. COIL
SELECTION PARAMETERS ACCESSORIES - E/F RELEASE • VERSIONS : 1) FIXED SETTINGS OF 10%, 20% OF In & 2) FIXED SETTINGS OF 30%, 40%, 50% OF In • FOR E/F PROTECTION • ONLY IN CONJUNCTION WITH THERMOMAGNETIC RELEASE • FOR 3 PHASE 4 WIRE SYSTEM, FOURTH CT REQUIRED
SELECTION PARAMETERS ACCESSORIES - LOCKS & INTERLOCKS • LOCKABLE TRIP PUSH BUTTON (CAN ALSO BE USED FOR INTERLOCKING TWO OR MORE CBs) • ISOLATED/ANY POSITION LOCK (CAN ALSO BE USED FOR INTERLOCKING TWO OR MORE CBs) • RACKING INTERLOCK
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB • FOR - TWO I/C + ONE B/C SYSTEM - THREE I/C + TWO B/C SYSTEM • SUITABLE FOR ALL TYPES OF ACBs (MF, MDO, EF & EDO)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB TWO I/C + ONE B/C SYSTEM TRANSFORMER 1600 KVA
G
PCC
)A
21
)
22
)
13
)
11
A
12
STANDBY GENERATOR 1250 KVA
)A 23
)
24
TWO A TYPE KEYS ARE PROVIDED
)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY LTPB THREE I/C + TWO B/C SYSTEM
G
PCC
)A
21
)
22
)
23
)
14
)
11
A
STANDBY G GENERATORS
12
)A
24
)
15
)
TRANSFORMER 1600 KVA
B
13
)B
25
)
26
TWO A TYPE KEYS & ONE B TYPE KEY ARE PROVIDED
)
SELECTION PARAMETERS MECHANICAL INTERLOCKING BY ISOLATED POSITION LOCK • FOR - TWO I/C + ONE B/C SYSTEM - THREE I/C + TWO B/C SYSTEM • SUITABLE FOR ONLY DRAW-OUT ACBs (MDO & EDO)
SELECTION PARAMETERS ACCESSORIES - MICROSWITCHES FOR ELECT. INDICATIONS • SERVICE/TEST/ISOLATED POSITION INDICATION
• UNDER VOLTAGE/SHUNT/EARTH FAULT RELEASE TRIP INDICATION • O/L & S/C TRIP INDICATION - COMMON & SEPARATE
SELECTION OF ACB BASIC CRITERIA CB SHOULD HAVE ADEQUATE : • • • • •
RATED VOLTAGE, Ue RATED CURRENT, In RATED S/C BREAKING CAPACITY, Icu /Ics RATED S/C MAKING CAPACITY, Icm RATED SHORT TIME WITHSTAND CURRENT, Icw • DISCRIMINATION WITH OTHER CBs & FUSES
EXAMPLE OF ACB SELECTION SELECTION OF ACB ‘11’, ‘21’ & ‘31’ IN THE SHOWN
SINGLE LINE DIAGRAM
SINGLE LINE DIAGRAM TRANSFORMER 1600 KVA
PCC
)
22
)
)
12 13
F1
350 A
)
11 21
STANDBY GENERATOR 1250 KVA
G
F2
) 23
24
300 A
300 A
)
MCC
BUSBAR U/G CABLE
F3
)
31
)
M1
50HP
)
M2
M3
M4
100HP
30HP
150HP
CB SDF STARTER
SYSTEM DATA TRANSFORMER : 11/0.433 KV 1600 KVA
STANDBY GENERATOR : UrG = 415 V 1250 KVA INDUCTION MOTORS : M1, IrM = 70A M2, IrM = 135A M3, IrM = 40A M4, IrM = 200A
AIR CIRCUIT BREAKER ‘11’ REQUIRED CURRENT RATING TRANSFORMER FL CURRENT = 1600 × 1000 3 × 433 =
2134 A
CONSIDERING 10% OVERLOADING, TOTAL CURRENT = 1.1 × 2134 = 2347 A
In OF CB ‘11’ 2347 A
AIR CIRCUIT BREAKER ‘11’ REQUIRED S/C BREAKING CAPACITY
Icu OF CB ‘11’ IK SUPPLIED BY TRANSFORMER AT F1 38.77 KA
AIR CIRCUIT BREAKER ‘11’ REQUIRED S/C MAKING CAPACITY
Icm OF CB ‘11’ IP SUPPLIED BY TRANSFORMER AT F1 87.71 KA(PEAK)
AIR CIRCUIT BREAKER ‘21’ REQUIRED CURRENT RATING SAME AS FOR ACB ‘31’
REQUIRED S/C MAKING & BREAKING CAPACITY SAME AS FOR ACB ‘11’
AIR CIRCUIT BREAKER ‘31’ REQUIRED CURRENT RATING
In OF CB ‘31’ (IrM) (70 + 135 + 40 + 200) 445 A
AIR CIRCUIT BREAKER ‘31’ REQUIRED S/C BREAKING CAPACITY
Icu OF CB ‘31’ IK SUPPLIED BY TRANSFORMER AT F3 15.67 KA
AIR CIRCUIT BREAKER ‘31’ REQUIRED S/C MAKING CAPACITY
Icm OF CB ‘31’ IP SUPPLIED BY TRANSFORMER AT F3 27.7 KA(PEAK)
TIME BASED DISCRIMINATION SETTING OF DELAY TIMES FOR UPSTREAM ACBs MINIMUM IMPULSION TIME OF IMMEDIATE
UPSTREAM ACB SHOULD BE > TOTAL OPERATING TIME OF DOWNSTREAM ACB
TIME BASED DISCRIMINATION BETWEEN ACBs ‘11’, ‘21’ & ‘31’ SUPPOSE FOR ACB ‘31’ M.I.T. = 25 mSEC & T.O.T = 90 mSEC ACB ‘21’ ACB ‘11’
M.I.T. = 100 mSEC T.O.T. = 165 mSEC M.I.T. = 200 mSEC T.O.T = 265 mSEC
CURRENT BASED DISCRIMINATION BETWEEN ACBs ‘11’, ‘21’ & ‘31’ CURRENT BASED DISCRIMINATION IS NOT POSSIBLE BETWEEN ACB ‘11’ & ‘21’ SINCE FAULT LEVEL AT THEIR LOCATIONS ARE SAME CURRENT BASED DISCRIMINATION IS POSSIBLE BETWEEN ACB ‘21’ & ‘31’ IF S/C PICKUP SETTING OF ACB ‘21’ > IK AT F3
ACB SELECTION CHART OF VALUES OBTAINED CHARACTERISTICS
In
CB ‘11’
2347 A
CB ‘21’
445 A
CB ‘31’
445 A
Icu (RMS)
38.77 KA 38.77 KA 15.67 KA
Icm (PEAK)
87.71 KA 87.71 KA 27.7 KA
T.O.T. (mSEC) Icw
265 mSEC 165 mSEC 90 mSEC (38.77 KA FOR (38.77 KA FOR (15.67 KA FOR HT CB T.O.T.)
265 mSEC )
165 mSEC)
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