GE P743 User Manual

P74x/EN OP/
Na7
Operation
(OP) 5
-
38
MiCOM P741, P742
, P743
OP
3. ISOLATOR AND CIRCUIT BREAKER FUNCTION
3.1 Isolator State Monitoring Features
MiCOM relays can be set to monitor normally open (89A) and normally closed (89B) auxiliary
contacts of the isolators. Under healthy conditions, these contacts will be in opposite states.
Should both sets of contacts be open, this would indicate one of the following conditions:
• Auxiliary contacts / wiring defective
• Isolator is defective
• Isolator is in isolated position
Should both sets of contacts be closed, only one of the following two conditions would apply:
• Auxiliary contacts / wiring defective
• Isolator is defective
A normally open / normally closed output contact has to be assigned to this function via the
programmable scheme logic (PSL). The time delay is set to avoid unwanted operation during
normal switching duties. If any of the above conditions exist, an alarm will be issued after the
time delay set in the PSL.
In the PSL Qx must be used following the two options:
• 89A or 89B
• Both 89A and 89B
If both 89A and 89B are used then status information will be available and in addition a
discrepancy alarm will be possible. 89A and 89B inputs are assigned to relay opto-isolated
inputs via the PSL.
When only one status information can be wired to a Peripheral Unit, it is recommended to
use the 89B (open) and link it inversed through a NAND gate or an NOR gate to the Isolator
closed position in the PSL.
3.2 Circuit Breaker State Monitoring Features
MiCOM relays can be set to monitor normally open (52A) and normally closed (52B) auxiliary
contacts of the circuit breaker. Under healthy conditions, these contacts will be in opposite
states. Should both sets of contacts be open, this would indicate one of the following
conditions:
• Auxiliary contacts / wiring defective
• Circuit Breaker (CB) is defective
• CB is in isolated position
Should both sets of contacts be closed, only one of the following two conditions would apply:
• Auxiliary contacts / wiring defective
• Circuit Breaker (CB) is defective
If any of the above conditions exist, an alarm will be issued after a 200ms time delay. A
normally open / normally closed output contact can be assigned to this function via the
programmable scheme logic (PSL). The time delay is set to avoid unwanted operation during
normal switching duties.
In the PSL CB AUX could be used or not, following these options:
• None
• Both 52A and 52B (triphase - 2 optos)
• Both 52A and 52B (per phase - 6 optos)

GE P743 Specifications

General

Brand	GE
Model	P743
Category	Relays
Language	English