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

Repetitive Tripping

Indication	Probable cause	Checks or repairs
SD	Supply voltage to the MX 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 MXshunt trip release applied unintentionally.	Check that the release connection is correct compared to the installation diagram.
SD	Operating temperature too high.	Check the switchboard ventilation and the temperature in the room.
SDV	Inappropriate earth-leakage protection setting.	Check the value of the natural leakage current. Depending on the results: Isolate the equipment which had excessive natural leakage current Or raise the earth-leakage protection setting, observing the safety rules.
SDV	Transient ground fault on the equipment.	Check whether the fault coincides with commissioning an item of equipment. Depending on the results: Repair the equipment causing the fault. Isolate the equipment with excessive natural leakage current. Or raise the earth-leakage protection setting, observing the safety rules.

Circuit Breaker Fails to Close

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.