25 – 2
25.1 General Notes
A few facts about WL trip units and breakers will help the tester understand how best to accomplish the required testing quickly and easily.
Air Core Sensor Technology
WL Breakers are equipped with air-core current sensors (Rogowsky coils, also known as linear couplers) and, as such, the ETUs cannot be
tested by conventional secondary injection techniques.
Ground Fault Protection
WL Breaker trip units can be equipped with ground fault protection according to the table below. Ground fault protection cannot be disabled
if it has been installed at the factory. Setting the Ground Fault Mode is either done via switch (see below) or via menu
(page 9-44).
Figure 1
The ground fault pick-up points for the Ground Fault Alarm and Ground Fault Trip settings are independently configurable. The definitions of
the A - E dial settings are described below:
ETU Type Available Ground Fault Modes
ETU 745
Optional: 3 or 4 wire residual, and direct sensing, are both available with additional
ground fault protection module. Mode is set by switch.
ETU 755 / 776
Optional: 3 or 4 wire residual, and direct sensing, are both available with additional
ground fault protection module. Mode is set by soft setting.
Pick-up Setting Frame Size 1 Frame Size 2 Frame Size 3
A 100 A 100 A 400 A
B 300 A 300 A 600 A
C 600 A 600 A 800 A
D 900 A 900 A 1000 A
E 1200 A 1200 A 1200 A
Ground Fault Mode Switch
Ground Fault Trip
Pick-up Adjustment
Ground Fault Alarm
Pick-up Adjustment
Ground Fault Trip
Delay Adjustment
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