Troubleshooting

Introduction

Troubleshooting operations are described in the following tables, with the checks or repairs to be carried out in relation to the probable causes of the malfunction indicated. They are classified into the following events:

Repetitive tripping
Circuit breaker fails to close (manually operated circuit breaker)
Circuit breaker fails to close (motor-operated circuit breaker)
MicroLogic 5, 6 and 7 fault screens

Repetitive Tripping

Indication	Probable cause	Checks or repairs
SD	Supply voltage to the MN undervoltage trip release is too low or subject to significant variations	Check the power supply for the release (for example, a supply powering motors with high power ratings may be unstable). If so, connect the release to a clean or stable supply.
SD	Supply voltage to an MX shunt trip release applied unintentionally	Check that the release connection is correct compared to the installation diagram.
SD, SDE	Operating temperature too high	Check the switchboard ventilation and the temperature in the room.
SD, SDE, SDV Earth-leakage fault indicator (MicroLogic 4) Information on display screen (MicroLogic 7) Button R on VigiPacT Add-on in the out position (MicroLogic 5 and 6 with VigiPacT Add-on)	Inappropriate earth-leakage protection setting (MicroLogic 4 and 7 or VigiPacT Add-on)	Check the value of the natural leakage current. Depending on the results: Isolate the equipment with excessive natural leakage current Or raise the earth-leakage (VigiPacT Add-on) protection setting, observing the safety rules.
	Transient insulation fault on the equipment	Check whether the fault coincides with commissioning an item of equipment. Depending on the results: Repair the faulty equipment Isolate the equipment with excessive natural leakage current Or raise the earth-leakage (VigiPacT Add-on) protection setting, observing the safety rules.
SD, SDE Screen TriP (available only in MicroLogic 5, 6, and 7) then StoP	Operating temperature too high	Check the switchboard ventilation and the temperature in the room.

Circuit Breaker Fails to Close (Manually Operated Circuit Breaker)

Indication	Probable cause	Checks or repairs
SD	MX shunt trip release energized MN undervoltage trip release not energized	Check that the release connection is correct compared to the installation diagram.
OF	Circuit breaker interlocked	Check the installation and interlock diagram (mechanical or electrical) for both circuit breakers.

Indication

Probable cause

Checks or repairs

MX shunt trip release energized

MN undervoltage trip release not energized

Check that the release connection is correct compared to the installation diagram.

Circuit breaker interlocked

Check the installation and interlock diagram (mechanical or electrical) for both circuit breakers.

Circuit Breaker Fails to Close (Motor-Operated Circuit Breaker)

Indication	Probable cause	Checks or repairs
OF	Close instruction not operational	Check the Auto position of the selector on the front of the circuit breaker. Also check: The power supply to the motor mechanism, the motor voltage The voltage at the motor terminals on the motor mechanism The close command path

Indication

Probable cause

Checks or repairs

Close instruction not operational

Check the Auto position of the selector on the front of the circuit breaker.

Also check:

The power supply to the motor mechanism, the motor voltage
The voltage at the motor terminals on the motor mechanism
The close command path

MicroLogic 5, 6, and 7 Fault Screens

The following table shows the checks or repairs to be carried out according to the MicroLogic 5, 6, and 7 fault screens. For more information, refer to DOCA0141EN, ComPact NSXMicroLogic 5/6/7 Electronic Trip Units - User Guide.

Indication	Probable cause	Checks or repairs
Screen TriP then StoP	Serious fault on the MicroLogic trip unit: the trip unit can no longer provide protection	Change the trip unit urgently. The circuit breaker cannot be reset.
Screen Err	Fault on the MicroLogic trip unit	Change the trip unit on the next maintenance visit. The trip unit can still provide protection.
Screen Out	Acknowledgment of a latching alarm which has not been reset on the SDx module	Check the cause of the alarm and use the OK button to carry out the reset.

Indication

Probable cause

Checks or repairs

Screen TriP then StoP

Serious fault on the MicroLogic trip unit: the trip unit can no longer provide protection

Change the trip unit urgently.

The circuit breaker cannot be reset.

Screen Err