Troubleshooting: Unexpected Tripping

Circuit breaker opened without any over-current electrical fault.

The blue fault-trip reset button is not popped out and no trip cause LED is lit.

Drop in voltage to below the threshold detected by MN undervoltage release.

Check the voltage and the MN supply circuit (V > 0.85 Un).

An order (for example load-shedding) sent to the MX opening voltage release by another circuit breaker.

Check the parameters of the circuit breaker that sent the order.

Unnecessary opening order from the MX opening voltage release.

Determine the origin of the order and cancel it.

Circuit breaker trips in a shorter time than expected after attempt to close the circuit breaker.

The blue fault-trip reset button is popped out and the L trip cause LED is blinking red.

Thermal memory is still active and current on the line is above the Ir threshold.

Check whether there is still an overload on the line. If necessary, make a correction. For details of thermal memory, refer to DOCA0265•• MasterPacT MTZ - MicroLogic Active Control Unit - User Guide in Related Documents at the beginning of this guide.

The blue fault-trip reset button is popped out, the I trip cause LED is lit, and the ERMS LED is lit.

ERMS is active so circuit breaker opens at lower protection settings.

The ERMS function applies reduced protection settings for use during maintenance. Check whether maintenance is in progress. If ERMS is no longer necessary, disengage it to revert to normal protection settings.

Immediate tripping after an attempt to close the circuit breaker.

The blue fault-trip reset button is popped out and the L trip cause LED is blinking red.

Transient overcurrent when closing.

• Modify the distribution system or the control unit settings.

• Check the condition of the circuit breaker before putting it back into service.

Immediate tripping after an attempt to close the circuit breaker with activation of the blue fault-trip reset button.

–

Closing on a short-circuit.

Refer to MasterPacT MTZ critical cases.

Nuisance tripping of the circuit breaker with activation of the blue fault-trip reset button.

–

Blue fault-trip reset button is not pushed-in completely.

Push in the blue fault-trip reset button completely.

–

Transient overcurrent detected on the line and fast instantaneous trip setting is active in EcoStruxure Power Commission software.

Intended behavior. If necessary, adjust the settings in EcoStruxure Power Commission software.