Areva MiCOM P441, Technical Manual

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P44x/EN HW/E33 Relay Description
Page 12/44 MiCOM P441/P442 & P444
SK4 : The InterMiCOM board (available with next version C1.0) is used to connect to an
EIA(RS)232 link, allowing up to eight programmable signalling bits to be transferred from/to
the remote line end relay. A suitable EIA(RS)232 link must exist between the two line ends,
for example a MODEM, or via a compatible multiplexer (check compatibility before ordering
the relay).
The second rear comms/InterMiCOM board, and IRIG-B board are mutually exclusive since
they use the same hardware slot. For this reason two versions of second rear comms board
are available ; one with an IRIG-B input and one without. (See also the Cortec code in
P44x/EN BR).
2.8 Mechanical layout
The case materials of the relay are constructed from pre-finished steel which has a
conductive covering of aluminium and zinc. This provides good earthing at all joints giving a
low impedance path to earth which is essential for performance in the presence of external
noise. The boards and modules use a multi-point earthing strategy to improve the immunity
to external noise and minimise the effect of circuit noise. Ground planes are used on boards
to reduce impedance paths and spring clips are used to ground the module metalwork.
Heavy duty terminal blocks are used at the rear of the relay for the current and voltage signal
connections. Medium duty terminal blocks are used for the digital logic input signals, the
output relay contacts, the power supply and the rear communication port. A BNC connector
is used for the optional IRIG-B signal. 9-pin and 25-pin female D-connectors are used at the
front of the relay for data communication.
Inside the relay the PCBs plug into the connector blocks at the rear, and can be removed
from the front of the relay only. The connector blocks to the relay’s CT inputs are provided
with internal shorting links inside the relay which will automatically short the current
transformer circuits before they are broken when the board is removed.
The front panel consists of a membrane keypad with tactile dome keys, an LCD and 12
LEDs mounted on an aluminium backing plate.