FFC-MM Plantsite Power System Protection

Protection Coordination

Prepared By:

Syed Faraz IqbalApp. Engr. (Electrical)

CONTENTS

Introduction to Protection Coordination

Selective Coordination

Data Required for Coordination Study

Protection Coordination at FFC-MM

Anomalies in Protection Coordination Scheme

Recommendations

PROTECTION COORDINATION

Protective device coordination is the process of determining the "best fit" timing of current

interruption when abnormal electrical conditions occur.

The goal is to minimize an outage to the smallest extent possible.

Successful system design hinges on coordination of each relaying scheme.

SELECTIVE COORDINATION

ISOLATION of a faulted circuit from the remainder of the installation is MANDATORY in today's modern

electrical systems.

Power BLACKOUTS CANNOT be tolerated.

A properly engineered system will allow ONLY the protective device nearest the fault to open, leaving

the remainder of the system undisturbed and preserving continuity of service.

SELECTIVE COORDINATION

The faulted circuit is isolated by the selective operation of only that overcurrent protective device

closest to the overcurrent condition.

[1] The National Electrical Code, NFPA 70, The National Fire Protection Association, Inc., 2005 Edition.

“Localization of an overcurrent condition to restrict outages to the circuit or equipment affected, accomplished by the choice of overcurrent

protective devices and their ratings or settings.”[1]

Not Affected

B

C

D

Also Opens

Also Opens

Opens

Branch CircuitFault

A

B

C

D

Opens

Not Affected

Not Affected

Not Affected

De-EnergizedPortion of System Fault

De-EnergizedPortion of SystemA

Selectively Coordinated SystemNon Selective System

DATA REQUIRED

Single-line

diagram

System voltage levels

Impedances

Short-circuit and load

current data

Data required for

coordination study

G G G

124 AC 124 BC

42-G1A 42-G1B 42G2

124 DE

TG-701A6.3 KV10000 KVA, 14%

TG-701B6.3 KV10000 KVA, 14%

MG-7026.3 KV1900 KVA

52B

M

24

M

52A

152 CD 152 C1D1

MP 601C MP 604

TR1A-46.3/0.38kV2000 kVA, 6.25%

TR1B-46.3/0.38kV

2000 kVA, 6.25%

FFC-MM POWER SYSTEM

FOR LINE TO LINE FAULT OF 6000 AMPS ON LV BUSBAR:

G

124 AC42-G1A

TG-701A6.3 KV10000 KVA, 14%

52A

TR1A-42000 KVA, 6.25%

51

50

50

51

51

3000/1

200/1

1000/1

O/C Relay of 52A will pick up & trip the CB in 5 seconds.

O/C Relay of MV CB will pick up & trip the CB in 18

seconds.

O/C Relay of 42-G1A will NOT pick up as per IDMT

curves

Inst O/C Relay of 52A will NOT pick up as per IDMT

curves

FAULT AT LV BUSBAR

FOR LINE TO LINE FAULT OF 18000 AMPS (Pickup Current of Inst. O/C Relay 50 of 52A) ON LV BUSBAR:

G

124 AC42-G1A

TG-701A6.3 KV10000 KVA, 14%

52A

TR1A-42000 KVA, 6.25%

51

50

50

51

51

3000/1

200/1

1000/1

O/C Relay of 52A will pick up & trip the CB in 0.42

seconds.

O/C Relay of MV CB will pick up & trip the CB in 1.3

seconds.

O/C Relay of 42-G1A will pick up & trip the CB in 90

seconds.

FAULT AT LV BUSBAR

Inst. O/C Relay of 52A will also pick

up in 0.1 seconds and block the automatic changeover

FOR LINE TO LINE FAULT OF 43350 AMPS ON LV BUSBAR:

G

124 AC42-G1A

TG-701A6.3 KV10000 KVA, 14%

52A

TR1A-42000 KVA, 6.25%

51

50

50

51

51

3000/1

200/1

1000/1


seconds.

O/C Relay of MV CB will pick up & trip the CB in

0.42 seconds.

O/C Relay of 42-G1A will pick up & trip the CB in 3.8

seconds.

FAULT AT LV BUSBAR

Inst. O/C Relay of 52A will also

pick up in 0.1 seconds and block the automatic changeover

FOR LINE TO LINE FAULT OF 48000 AMPS (TR1A-4 Short Circuit Level) ON LV BUSBAR:

G

124 AC42-G1A

TG-701A6.3 KV10000 KVA, 14%

52A

TR1A-42000 KVA, 6.25%

51

50

50

51

51

3000/1

200/1

1000/1


seconds.

O/C Relay of MV CB will pick up & trip the CB in

0.36 seconds.


seconds.

FAULT AT LV BUSBAR

Inst O/C Relay of MV CB will NOT pick up as per IDMT

curves

Inst. O/C Relay of 52A will also

pick up in 0.1 seconds and block the automatic changeover

OBSERVATION # 01

On Occurrence Of Short Circuit Fault On LV Busbar,

The LV Incoming Circuit Breaker 52A will

trip until FaultCurrent Level

of app. 43KA as opposed to the current

understanding that MV CB always trips in case

of Short Circuit Fault On LV Busbar

FOR LINE TO LINE FAULT OF 275 AMPS ON MV SIDE OF T/F:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

51

50

51

67A

1000/1

1000/1

200/1

TR1A-46.3/0.38kV2000 kVA, 6.25%

FAULT AT MV SIDE OF T/F

O/C Relay of MV CB will pick up & trip the CB in 50 seconds.

O/C Relay of 42-G1A will NOT pick up as per IDMT

curves

Directional O/C Relay of 124 AC will NOT pick up as per

IDMT curves

FOR 6.3KV MAXIMUM SHORT CIRCUIT LEVEL CURRENT (22000 AMPS):

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

51

50

51

67A

1000/1

1000/1

200/1

TR1A-46.3/0.38kV2000 kVA, 6.25%


seconds.


seconds.

Directional O/C Relay of 124 AC will NOT sense the fault

current.

Inst. O/C Relay of MV CB will also pick up and trip the CB in 0.03 seconds.

Inst. O/C Relay of MV CB will NOT pick up as per IDMT

curves

FOR LINE TO LINE FAULT OF 4000 AMPS (Pickup Current of Inst. O/C Relay 50 of MV CB) ON MV SIDE OF T/F:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

51

50

51

67A

1000/1

1000/1

200/1

TR1A-46.3/0.38kV2000 kVA, 6.25%


seconds.


seconds.

Directional O/C Relay of 124 AC will NOT sense the fault

current

Inst. O/C Relay of MV CB will also pick up and trip the CB in 0.03 seconds.

FOR LINE TO LINE FAULT OF 1467 AMPS ON BUSBAR ‘A’:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

511000/1

67A

1000/1

124 BC 124 DE

GTG-701B6.3 KV10000 KVA, 14%

51

GMG-7026.3 KV1900 KVA

152 CD

42-G1B 42-G267B

1000/1

152 C1D1

1000/1

51 500/1

FAULT AT BUSBAR ‘A’

O/C Relay of 42-G1A & 42G1-B will pick up & trip the respective

CB’s in 20 seconds.

Directional O/C Relays on Busbar ‘A ‘ & Busbar ‘B’ will not sense the fault current.

Both Directional O/c Relays ‘67A’ & ‘67B’ in accordance

with their CT polarity are sensing the Fault Current

in the same direction as opposed to the required

scheme of sensing the Fault Current

in opposite directions.

OBSERVATION # 02

FOR LINE TO LINE FAULT OF 1467 AMPS ON BUSBAR ‘B’:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

511000/1

67A

1000/1

124 BC 124 DE

GTG-701B6.3 KV10000 KVA, 14%

51

GMG-7026.3 KV1900 KVA

152 CD

42-G1B 42-G267B

1000/1

152 C1D1

1000/1

51 500/1

FAULT AT BUSBAR ‘B’

Directional O/C Relay on Busbar ‘A’ will pick up & trip 124AC in 8

seconds.

Directional O/C Relay on Busbar ‘B’ will pick up & trip 124BC in 8

seconds.

O/C Relay of 42-G1B will pick up & trip the CB in 20

seconds.

FOR LINE TO LINE FAULT OF 1467 AMPS ON BUSBAR ‘C’:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

511000/1

67A

1000/1

124 BC 124 DE

GTG-701B6.3 KV10000 KVA, 14%

51

GMG-7026.3 KV1900 KVA

152 CD

42-G1B 42-G267B

1000/1

152 C1D1

1000/1

51 500/1

FAULT AT BUSBAR ‘C’


seconds.

Directional O/C Relays on Busbar ‘B’ will not sense the

fault current.


seconds.

FOR LINE TO LINE FAULT OF 1467 AMPS ON CABLE LINK:

G

124 AC

42-G1A

TG-701A6.3 KV10000 KVA, 14%

511000/1

67A

1000/1

124 BC 124 DE

GTG-701B6.3 KV10000 KVA, 14%

51

GMG-7026.3 KV1900 KVA

152 CD

42-G1B 42-G267B

1000/1

152 C1D1

1000/1

51 500/1

FAULT AT CABLE LINK


seconds.

Directional O/C Relays on Busbar ‘B’ will not sense the

fault current.


seconds.

O/C Relay of 152CD will pick up & trip the CB in 5

seconds.`

U/V Relay of 124DE will pick up & open the CB.

RECOMMENDATIONS

An extensive audit is needed to be carried out to check the Dot Notation of Current Transformers.

Secondary Current Injection Test should be planned in order to determine the correct behavior of Directional Relays in case of occurrence of fault on MV Busbars .

QUESTIONS………..?

External Wiring of Phase Fault detection relay CR

Pickup Current for Inst O/C Relay (50) of LV Busbar CB

TR1A-4 Short Circuit Level Current

FFC-MM Plantsite Power System Protection

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