Method Of Repair; Replacing The Complete Relay; Location Of Securing Screws For Terminal Block - GE MiCOM P40 Agile Technical Manual

P44x/EN MT/Hb6
(MT) 10-6
1.3

Method of Repair

If the relay should develop a fault while in service, depending on the nature of the fault, the
watchdog contacts will change state and an alarm condition will be flagged. Due to the
extensive use of surface-mount components faulty PCBs must be replaced as it is not
possible to perform repairs on damaged circuits. Therefore either the complete relay or just
the faulty PCB, identified by the in-built diagnostic software, can be replaced. Advice about
identifying the faulty PCB can be found in the Troubleshooting chapter.
The preferred method is to replace the complete relay as it ensures that the internal circuitry
is protected against electrostatic discharge and physical damage at all times and overcomes
the possibility of incompatibility between replacement PCBs. However, it may be difficult to
remove an installed relay due to limited access in the back of the cubicle and scheme wiring
rigidity.
Replacing PCBs can reduce transport costs but requires clean, dry conditions on site and
higher skills from the person performing the repair. However, if the repair is not performed
by an approved service centre, the warranty will be invalidated.
Before carrying out any work on the equipment, the user should be familiar with the
Safety and Installation chapters of this manual. This should ensure that no damage is
caused by incorrect handling of the electronic components.
1.3.1

Replacing the Complete Relay

The case and rear terminal blocks have been designed to facilitate removal of the complete
relay should replacement or repair become necessary without having to disconnect the
scheme wiring.
Before working at the rear of the relay, isolate all voltage and current supplies to the relay.
Note:
Disconnect the relay earth, IRIG-B (Central unit only) and fibre optic connections, as
appropriate, from the rear of the relay.
Two types of terminal block used on the relay, medium and heavy duty. They are fastened to
the rear panel using crosshead screws.
Figure 1: Location of securing screws for terminal block
Note:
The MiCOM range of relays have integral current transformer shorting switches that
will close when the heavy duty terminal block is removed.
The use of a magnetic-bladed screwdriver is recommended to minimise the risk of the
screws being left in the terminal block or lost.
Maintenance
MiCOM P40 Agile P442, P444