Zero Sequence Cbct Installation - GE 339 Instruction Manual

ELECTRICAL INSTALLATION

Zero sequence CBCT installation

SHIELDED TWISTED PAIR
2–14
Figure 17: Residual ground CT connection
A
B
C
1A/5A
The exact placement of a zero sequence CT to properly detect ground fault current is
shown below. If the CT is placed over a shielded cable, capacitive coupling of phase current
into the cable shield during motor starts may be detected as ground current unless the
shield wire is also passed through the CT window. Twisted pair cabling on the zero
sequence CT is recommended
Figure 18: Zero sequence core balance (CT) installation
U SHIELDED CABLE
Source
A B C
LOAD
PHASE A CT
PHASE B CT
PHASE C CT
E5 D5 E6 D6 E7 D7
COM 1A/5A COM 1A/5A COM
PHASE A PHASE B PHASE C
CURRENT INPUTS
Ground connection to neutral
must be on the source side
G
Ground
outside CT
SHIELDED TWISTED PAIR
339 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 2: INSTALLATION
E8 D8
1A/5A COM
GROUND
896827.cdr
SHIELDED CABLE
Source
A B C
LOAD
Stress cone
shields
To ground;
must be on
load side
896791.CDR