Phase Current Inputs (Io_A Module) - GE Multilin MM300 Quick Start Manual

ELECTRICAL INSTALLATION
CAUTION:

Phase current inputs (IO_A module)

Power flow
D2
D1 D3 D4
CT1 CT2
Phase current inputs
Residual Ground Connection
10
To ensure that all devices in a daisy-chain are at the same potential, it is imperative
that the common terminals of each RS485 port are tied together and grounded only
once, at the master or at the MM300. Failure to do so may result in intermittent or
failed communications.
The source computer/PLC/SCADA system should have similar transient protection devices
installed, either internally or externally. Ground the shield at one point only, as shown in
the figure above, to avoid ground loops.
Correct polarity is also essential. The MM300 IEDs must be wired with all the positive (+)
terminals connected together and all the negative (–) terminals connected together. Each
relay must be daisy-chained to the next one. Avoid star or stub connected configurations.
The last device at each end of the daisy-chain should be terminated with a 120 ohm ¼
watt resistor in series with a 1 nF capacitor across the positive and negative terminals.
Observing these guidelines will ensure a reliable communication system immune to
system transients.
Figure 2-13: Typical phase current input connections
D1
D5 D6 D7 D8
CT3 G/F
Power flow Power flow
D2
D3 D4 D5 D6 D7 D8
CT1 CT2 CT3 G/F
Phase current inputs
Direct Connection
MM300 MOTOR MANAGEMENT SYSTEM – QUICKSTART GUIDE
CHAPTER 2: INSTALLATION
Power flow Power flow
D1 D2 D3 D4 D5 D6 D7 D8
CT1 CT2 CT3 G/F
Phase current inputs
Two CT Connection
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