Feeder Protection / Transformer Backup Protection

Additional Details

JNC 268 N / JNC 268 A / JNC 268 L :

The relay measures the line current from each of the line CTs and if the current exceeds the set threshold, then relay extends a trip signal after an operating time. The relay's “operating time” is determined by selecting “definite time” or one of the six “inverse time” characteristics.

A sensitive earth fault or restricted earth fault (suitable for high impedence REF scheme) is provided in the relay.The input to sensitive earth fault protection can be connected in two ways. First one the residual current derived from three phase current transformers, and second is low output core balance current transformer can be connected. The input to restricted earth fault protection will be derived from neutral CT output with external stabilizing resistor.The relay has facility to monitor circuit breaker operation through 52a or 52b aux contacts of circuit breaker.

4 programmable digital inputs (PDI) and 4 programmable digital outputs are provided and can be used to synthesize logic along with some internal digital inputs i.e.(phase OC pickup, Earth fault pickup, Phase high set trip, Earth fault OC trip, Earth fault high set trip,etc). Together, this feature can be effectively used to reduce the number of aux. tripping relays in a protection scheme. The trip relay (B1-B2) can be operated either when any one / more of the protection scheme provided inside JNC 268 x initiates the relay or any/more of the PDI initiates the same relay.

Each PDO has independent timer. Each PDI has programmable mask facility.The relay in-built breaker trip circuit supervision and dedicated alarm contact to indicate trip circuit failure.

JNC 268 A :

Provides Multi shot auto re-closer facilitates automation of breaker operation. Auto re-closer can be programmed to provide a maximum of five shots. “Dead time” starts when a trip signal is provided due to the occurrence of a fault involving L-L or L-G or L-L-G or L-L-L or L-L-L-G. After an elapse of a time interval equal to “dead time”, closing command will be extended.

The “reclaim time” timer starts at the instant when the “dead time” timer expires. If after extending the “breaker close” signal an over current fault was detected before the “reclaim time” timer reached its terminal count, then the relay understands that the fault in the system is still persisting and the over current relay will issue a trip signal. The relay tries to close the breaker for a maximum of the programmed number of shots before it choses to lockout. The relay can be configured for independent trip sequence as IDMT or Def. time

JNC 268 L :

The relay monitors line current even after the trip condition to ensure breaker operation. Even if small current exist in the line the relay sends trip command to adjacent or backup breaker after definite operating time. The current threshold and definite time required to detect breaker failure are programmable.

Characteristics:

Suitable for 1A / 5A relay rating

Choice of 6 IDMT curve and definite time

History of 6 latest faults along with settings

Self supervision facility

Breaker status monitoring

In-built breaker trip circuit supervision

Disturbance records (DR) in IEEE COMTRADE

format – Optional

Event Records (ER) – Optional

Programmable digital inputs and outputs

MODBUS open protocol over RS – 485 port

MODBUS protocol over RS – 232 port

Draw out facility with inbuilt CT shorting

Application:

The relay provides time graded phase, earth fault (2 stage) protection along with 5 shot auto recloser and SCADA capability.

Settings:

Operating characteristics (Separate for Phase & Earth fault ):

1) 3.0s Normal Inverse

2) 1.3s Normal Inverse

3) 1.5s Very Inverse

4) 0.8s Extremely Inverse

5) 0.6s Extremely Inverse

6) 13.3s Long Inverse

7) Definite Time

Phase OC (IDMT) : 20 to 200% in steps of 5%

Phase OC (Def time) : 20 to 500% in steps of 5%

Earth fault (IDMT) : 5 to 80% in steps of 1%

Earth fault (Def time) : 5 to 100% in steps of 1%

SEF (Def time) : 1 to 16% in steps of 0.5%

REF (Instantaneous) : 2 to 80% in steps of 1%

TMS (Ph & E/F) : 0.02 to 1.0 in steps of 0.01

Definite time (Separate for Ph, E/F & SEF ): Instantaneous to 25.0s in steps of 0.1s

Phase High set : 100 to 3200% in steps of 100%

Earth fault High set : 50 to 1000% in steps of 50%

High set operating time ( Ph & E/F ) : Instantaneous to 500ms in steps of 50ms

Breaker monitoring :  1) 52a monitoring, 2) 52b monitoring, 3) None

RS232 communication : MODBUS Protocol 9-Pin D at front end

RS485 communication : MODBUS Protocol Isolated RS485 at rear end

No. of DR (optional) : Two

Duration of DR  :0.86s (0.46s Pre-fault and 0.4s Post-fault) 

ER (optional) : 120 events

 JNC 268 A SETTINGS

Max. Shots (re-closing) : Maximum of 5

Dead time 1 to 5 : 0.5 to 250s in steps of 0.1s

Reclaim time : 10 to 250s in steps of 1s

Cold load pickup (CLP) : 2 to 16 times the OC (IDMT)

CLP Delay : 0.05s to 1.0s in steps of 0.01s

JNC 268 A SETTINGS : 

Max. Shots (re-closing) : Maximum of 5

Dead time 1 to 5 : 0.5 to 250s in steps of 0.1s

Reclaim time : 10 to 250s in steps of 1s

Cold load pickup (CLP) : 2 to 16 times the OC (IDMT) 

CLP Delay : 0.05s to 1.0s in steps of 0.01s