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Neutral conductor tripping test
The long-time delayed short-circuit tripping function for the neutral conductor and the trip unit circuitry for ETU type 776 can be tested using
the test device.The current sensor for the neutral conductor must be attached
(page 9-97) and the "Neutral conductor protection" function
must be switched on (page 9-13).
1 Charge the circuit breaker
2 Close the circuit breaker
3 Press the [N] button
The circuit breaker will trip after the set long-time delay time, plus approx. 2 seconds processing time, has elapsed. If the test device has
completed a test without faults, the "ETU STATUS" LED will light up continuously green. If a fault is detected, the LED will flash. The type of
flashing indicates what type of fault is present (fault codes are listed on page 9-104).
Ground-fault tripping test
The ground-fault tripping function and the trip unit circuitry of ETU types 745-746 with an installed ground-fault protection module (with trip-
ping function WLGFM48 or WLGFM76) can be tested using the test device. The current sensor for the neutral conductor (page 9-97) and/or
the iron-core ground-fault sensor (page 9-44) must be attached.
1 Charge the circuit breaker
2 Close the circuit breaker
3 Press the [G] button
The circuit breaker will trip after the set ground-fault tripping delay time, plus approx. 2 seconds processing time, has elapsed. If the test
device has completed a test without faults, the "ETU STATUS" LED will light up continuously green. If a fault is detected, the LED will flash.
The type of flashing indicates what type of fault is present (fault codes are listed on page 9-104).
Testing the measured value display
This function works by inputting a signal into the trip unit. The signal is displayed as a single-phase current on the trip unit's display, and the
current's measured value is also transmitted via the communication interface to the connected
CublicleBUS modules and the connected
Modbus RTU / PROFIBUS DP networks.
This feature only works with an integrated display (WLETU745 with WLLCD48, WLETU776), and communicates test signals when a
communication interface and/or a CublicleBUS module is installed on the trip unit.This feature does not work when a MeteringPLUS
(WLMETERP) module is installed.
1 Connect 24 V DC to power the trip unit.
2 Press the [I] and [N] buttons simultaneously
A single-phase test signal is fed into the trip unit, which simulates a single-phase load current for the ETU. The local display, the connected
communications and connected
CublicleBUS modules output this current value. The test signal will specify the simulated value to the first
phase for 30 seconds, before changing to the next phase. The cycle runs in the order L1, L2, L3, N, G. The test cycle is completed when all
phases have been tested.
Activation the trip unit
To activate the trip unit, press the "N" and "G" buttons simultaneously.
The trip unit will remain activated until another button on the handheld test device (WLTS) is depressed.
With this function, the "T.U.-Error"-LED can be checked if the status test had finished with the error "Trip unit defective".
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