Troubleshooting: Unexpected Tripping

@writer: (confirmed 12/11/24) topic shared in Masterpact MTZ1 User Guide (DOCA0100), Masterpact MTZ2/3 User Guide (DOCA0101), and in the appendix in Masterpact MTZ End-user and Manufacturer Maintenance Procedures (DOCA0103 and DOCA0104). Any changes made will be made in all these guides.

Definition

Unexpected tripping is tripping that is not caused by a protection function during normal operation or by tests.

Troubleshooting

Problem description	Symptom	Probable causes	Solutions
Device 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 device.	Check the parameters of the device that sent the order.
		Unnecessary opening order from the MX opening voltage release.	Determine the origin of the order and cancel it.
Device trips in a shorter time than expected after attempt to close the device.	The blue fault-trip reset button is popped out and the Ir LED is lit.	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 DOCA0102•• MasterPacT MTZ - MicroLogic X Control Unit - User Guide in Related Documents at the beginning of this guide.
	The blue fault-trip reset button is popped out, the Ir or Isd LED is lit, and the ERMS LED is lit.	ERMS is active so device 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.
	–	The tripping curves (A or B) have been modified, or the control unit is not set to the usual set of tripping curves (A or B).	This might be a change in intended behavior so not a problem. Check the tripping curve definitions are describing the intended behavior. Modify the definitions if necessary.
Immediate tripping after an attempt to close the device.	The blue fault-trip reset button is popped out and the Ir LED is lit.	Transient overcurrent when closing.	Modify the distribution system or the control unit settings. Check the condition of the device before putting it back into service.
Immediate tripping after an attempt to close the device with activation of the blue fault-trip reset button.	–	Closing on a short-circuit.	Refer to MasterPacT MTZ critical cases.
Nuisance tripping of the device 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.