GE Multilin 345, Instruction Manual

Page: 47 / 254

CHAPTER 2: INSTALLATION ELECTRICAL INSTALLATION
345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 2–19
Figure 2-23: RMIO wiring diagram
N OTE
NOTE:
F5, F7, and F8 refer to terminals shown on the above 345 Terminal Identification diagrams.
Phase sequence and transformer polarity
For correct operation of the relay features, the user must follow the instrument
transformer polarities, shown in the Typical Wiring Diagram. Note the solid square
markings shown with all instrument transformer connections. The phase sequence is user
programmable for either ABC or ACB rotation.
Current inputs
The 345 relay has eight (8) channels for AC current inputs, each with an isolating
transformer. There are no internal ground connections on the current inputs. Current
transformers with 1 to 6000 A primaries may be used.
CAUTION:
Verify that the relay’s nominal input current of 1 A or 5 A matches the secondary rating
of the connected CTs. Unmatched CTs may result in equipment damage or inadequate
protection.
CAUTION:
IMPORTANT: The phase and ground current inputs will correctly measure up to 20
times the current input’s nominal rating. Time overcurrent curves become horizontal
lines for currents above the 20 × CT rating. This becomes apparent if the pickup level is
set above the nominal CT rating.
CAUTION:
Before working on CTs, they MUST be short circuited.
SCADA, PLC, OR
PERSONAL COMPUTER
OPTOCOUPLER
DATA
RMIO
SHIELD
896740A1.CDR
(*) TERMINATING IMPEDANCE AT EACH END
(typically 120 ohms and 1 nF)
TWISTED PAIR
RMIO +
RMIO -
COMMON
GROUND THE SHIELD AT THE
SCADA/PLC/COMPUTER ONLY
OR THE MM300 ONLY
DATA
OPTOCOUPLER
B1
B2
B3
Z (*)
T
3 Series IED
F7: RMIO+
F5: COM
F8: RMIO-
– +
To switchgear
ground bus
Control power
L N