Phase Sequence And Transformer Polarity; Current Inputs - GE Multilin 345 Instruction Manual

CHAPTER 2: INSTALLATION
3 Series IED
OPTOCOUPLER
DATA
SCADA, PLC, OR
PERSONAL COMPUTER
GROUND THE SHIELD AT THE
SCADA/PLC/COMPUTER ONLY
(*) TERMINATING IMPEDANCE AT EACH END
(typically 120 ohms and 1 nF)
NOTE:
NOTE

Phase sequence and transformer polarity

Current inputs

CAUTION:
CAUTION:
CAUTION:
345 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 2-23: RMIO wiring diagram
Z (*) SHIELD
T
F7: RMIO+
F8: RMIO-
F5: COM
OR THE MM300 ONLY
F5, F7, and F8 refer to terminals shown on the above 345 Terminal Identification diagrams.
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.
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.
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.
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.
Before working on CTs, they MUST be short circuited.
TWISTED PAIR
B1 RMIO +
B2 RMIO -
B3 COMMON
ELECTRICAL INSTALLATION
To switchgear
ground bus
RMIO
Control power
OPTOCOUPLER
DATA
896740A1.CDR
+
–
N L
2–19