GE MOTOR MANAGEMENT RELAY 469, Инструкция по эксплуатации

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GE Power Management 469 Motor Management Relay 2-11
2 INSTALLATION 2.2 ELECTRICAL
2
The 469 measures up to 5 A secondary current if the 1 A / 5 A tap is used. Since the conversion range is rela-
tively small, the 1 A or 5 A option is field programmable. Proper selection of this setpoint ensures proper read-
ing of primary ground current. The 1 A / 5 A ground CT chosen must be capable of driving the 469 ground CT
burden (see Section 1.2: SPECIFICATIONS on page 1–5). The 469 measures up to 25 A of primary ground
current if this tap is used in conjunction with the GE Power Management core balance CT.
The zero-sequence connection is recommended. Unequal saturation of CTs, size and location
of motor, resistance of power system and motor core saturation density, etc., may cause false
readings in the residually connected GF circuit.
Only one ground input should be wired – the other input should be unconnected.
The exact placement of a zero-sequence CT to detect only ground fault current is shown below. If the core bal-
ance CT is placed over 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 2–13: CORE BALANCE GROUND CT INSTALLATION
NOTE
NOTE
SHIELDED CABLE
UNSHIELDED CABLE