Areva MiCOM P441, Technical Manual

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Commissioning P44x/EN CM/E33
MiCOM P441/P442 & P444 Page 45/54
8.3.2 Replacing a PCB
If the relay fails to operate correctly refer to Chapter P44x/EN PR, ‘Problem Analysis’, to help
determine which PCB has become faulty.
To replace any of the relay’s PCBs it is necessary to first remove the front panel.
Before removing the front panel to replace a PCB the auxiliary supply must be
removed. It is also strongly recommended that the voltage and current transformer
connections and trip circuit are isolated.
Open the top and bottom access covers. With size 60TE cases the access covers have two
hinge-assistance T-pieces which clear the front panel moulding when the access covers are
opened by more than 90
°
, thus allowing their removal.
If fitted, remove the transparent secondary front cover. A description of how to do this is
given in Chapter P44x/EN IT, ‘Introduction’.
By slightly bending the access covers at one end, the end pivot can be removed from its
socket and the access cover removed to give access to the screws that fasten the front
panel to the case.
The size 40TE case has four crosshead screws fastening the front panel to the case, one in
each corner, in recessed holes. The size 60TE case has an additional two screws, one
midway along each of the top and bottom edges of the front plate. Undo and remove the
screws.
DO NOT REMOVE THE SCREWS WITH THE LARGER DIAMETER HEADS WHICH ARE
ACCESSIBLE WHEN THE ACCESS COVERS ARE FITTED AND OPEN. THESE
SCREWS HOLD THE RELAY IN ITS MOUNTING (PANEL OR CUBICLE).
When the screws have been removed, the complete front panel can be pulled forward and
separated from the metal case. Caution should be observed at this stage because the front
panel is connected to the rest of the relay circuitry by a 64-way ribbon cable.
The ribbon cable is fastened to the front panel using an IDC connector; a socket on the cable
itself and a plug with locking latches on the front panel. Gently push the two locking latches
outwards which will eject the connector socket slightly. Remove the socket from the plug to
disconnect the front panel.
F E D C B A
Power supply
board
Power supply module Input module
Relay board Not used IRIG-B board Input board Transformer board
P0150ENa
FIGURE 22 - P441 PCB/MODULE LOCATIONS (VIEWED FROM FRONT)