Areva MiCOM P341, Руководство по эксплуатации

Страница: 78 / 282

P341/EN O/B11 Operation Guide
CHAPTER 3 Commissioning and
Page 24/80 Maintenance
MiCOM P341
8.2.4 Measurement accuracy
If the power system is energised, the values measured by the relay can be compared
with known system values to check that they are in the approximate range that is
expected. If they are then the analogue/digital conversion and calculations are being
performed correctly by the relay. Suitable test methods can be found in Sections 6.1
and 6.2 of this chapter.
Alternatively, the values measured by the relay can be checked against known values
injected into the relay via the test block, if fitted, or injected directly into the relay
terminals. Suitable test methods can be found in Sections 4.2.9 and 4.2.10 of this
chapter. These tests will prove the calibration accuracy is being maintained.
8.3 Method of repair
If the relay should develop a fault whilst 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 should be
replaced as it is not possible to perform repairs on damaged circuits. Thus 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 Chapter 4,
‘Problem Analysis’.
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 rigidity of the scheme wiring.
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 CONTENTS OF THE SAFETY AND
TECHNICAL DATA SECTIONS AND THE RATINGS ON THE EQUIPMENT’S
RATING LABEL. THIS SHOULD ENSURE THAT NO DAMAGE IS CAUSED BY
INCORRECT HANDLING OF THE ELECTRONIC COMPONENTS.
8.3.1 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: The MiCOM range of relays have integral current transformer shorting
switches which will close when the heavy duty terminal block is removed.
Disconnect the relay earth connection from the rear of the relay.