Ground-Fault Protection Modules - Siemens UL 489 Operating Instructions Manual

Replacing Rating Plug
Circuit breaker may trip.
If the trip settings are changed while the breaker is closed (and under load) the breaker may trip.
Adjust parameters only when the circuit breaker is in the open position.
9.1.8

Ground-fault protection modules

WL trip units can be optionally equipped with modules that add ground fault protection. The modules provide either an alarm-only function
or alarm-and-trip functionality.
The modules can be added or removed as necessary in the field.
 (page 9-12)
Settings are found on
The following combinations are possible:
Trip unit
ETU745
ETU776
The following options exist for ground-fault detection:
- Vector sum of the three phase currents plus neutral, if a neutral sensor is connected (residual sensing).
- Direct measurement of the ground-fault current using a separate 1200 A : 1 A iron-core ground fault sensor.
The direct-sense input to the trip unit has the following current-carrying capability:
- max. 1 A continuous
- max. 5 A for 0.5 sec.
Note
If the circuit breaker is applied in a 4-wire system, and residual ground
fault protection is desired, it is strongly recommended that a WL neutral
sensor (WLNCT2, WLNCT3) be used on the neutral to facilitate the 
correct vector-summation of the phase currents with the neutral. Failure
to apply a neutral sensor may result in erroneous GF alarm and trips.
Note
Output of alarms and messages is possible via COM and c
modules.
9 – 44
1
OPEN
Ground-fault protection module
GFM A 745 (alarm only)
GFM AT 745 (alarm and trip)
GFM A 776 (alarm only)
GFM AT 776 (alarm and trip)
NOTICE
3
2