Alstom MiCOM P846, Technical Manual

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Installation P846/EN IN/D
MiCOM P846 (IN) 15-9
IN
6.2 EIA(RS)485 port
Connections to the EIA(RS)485 port are made using ring terminals. It is recommended that
a 2 core screened cable is used with a maximum total length of 1000m or 200nF total cable
capacitance. A typical cable specification would be:
Each core: 16/0.2mm copper conductors
PVC insulated
Nominal conductor area: 0.5mm
2
per core
Screen: Overall braid, PVC sheathed
See SCADA Communications (P846/EN CT) for detailed discussion on setting up an
EIA(RS)485 bus.
6.3 IRIG-B connections (if applicable)
The IRIG-B input and BNC connector have a characteristic impedance of 50
Ω
. It is
recommended that connections between the IRIG-B equipment and the relay are made
using coaxial cable of type RG59LSF with a halogen free, fire retardant sheath.
6.4 EIA(RS)232 front port
Short term connections to the EIA(RS)232 port, located behind the bottom access cover, can
be made using a screened multi-core communication cable up to 15m long, or a total
capacitance of 2500pF. The cable should be terminated at the relay end with a 9-way, metal
shelled, D-type male plug. The pin allocations are detailed in section 1.8 of Getting Started
(P846/EN GS).
6.5 Download/monitor port
Short term connections to the download/monitor port, located behind the bottom access
cover, can be made using a screened 25-core communication cable up to 4m long. The
cable should be terminated at the relay end with a 25-way, metal shelled, D-type male plug
and linked as a parallel data connection.
6.6 Earth connection
Every relay must be connected to the cubicle earth bar using the M4 earth studs in the
bottom left hand corner of the relay case. The minimum recommended wire size is 2.5mm
2
and should have a ring terminal at the relay end.
To prevent any possibility of electrolytic action between brass or copper earth conductors
and the rear of the relay, precautions should be taken. Examples include placing a nickel-
plated washer between the conductor and the relay case, or using tinned ring terminals.
6.7 CT inputs
I
A
, I
B
and I
C
are low level CT with a range of 16 I
N
.
I
N
sensitive is a sensitive CT, with a range of 2 I
N
giving better resolution at the expense of
dynamic range.