Schneider NSX micrologic trip units

Geez:

Had a callout to a block of flats last night where one of these devices (250A) had tripped. Cause seems to be a fault on a lift, as its own 100A downstream device also tripped, so obviously not set correctly for discrimination. Problem is that after restoring the 250A device it now trips on a very small load, literally a couple of amps per phase. Wondered if anyone has seen this before? has the trip unit been destroyed by the fault or has its electronics got into a pickle?


As it was night time there was not enough load to even light the micrologic display. As a temp clear I managed to move the circuit onto an unused 100A device in the panel but for 13 flats and the communals dont know how long ill get away with that.


PS can the trip units be replaced safely on these units without isolating the upstream device, this would be a 1600A ACB feeding a very large development.


Thanks in advance


Tom

Does page 13 help at all?

Compact NSX Micrologic 5/6/7 - Electronic Trip Units - User Guide - 01/2020 (schneider-electric.com)


P.S. Internal Power Supply for Micrologic 5 and 6 Trip Units The protection functions and the test functions of Micrologic 5 and 6 trip units operate with the current through the internal current transformers (CT). When the load current is higher than 20% of the rated current In, the internal current supply provides the power supply for the full functioning of the Micrologic trip unit. This includes:  The Micrologic display screen and LEDs  The maintenance and diagnostic functions To provide a power supply to the Micrologic 5 or 6 trip unit when the load is below 20% of the rated current In, and maintain the full functioning of the Micrologic trip unit, one of the following optional power supplies can be used:  An external 24 Vdc power supply connected permanently to the Micrologic trip unit  A power supply connected temporarily to the test port on the Micrologic trip unit:  Pocket battery  PC through USB maintenance interface Each optional Micrologic power supply is described further.


P.P.S.

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH  If the trip unit displays a St0p screen, replace the Micrologic trip unit immediately.  If trip unit displays a fault screen, do not close the circuit breaker again without first inspecting and, if necessary, repairing the downstream electrical equipment.  Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E or CSA Z462 or local equivalent.  This equipment must only be installed and serviced by qualified electrical personnel.  Turn off all power supplying this equipment before working on or inside equipment.  Always use a properly rated voltage sensing device to confirm that power is off.  Replace all devices, doors, and covers before turning on power to this equipment. Failure to follow these instructions will result in death or serious injury

Z.

Geez:

Had a callout to a block of flats last night where one of these devices (250A) had tripped. Cause seems to be a fault on a lift, as its own 100A downstream device also tripped, so obviously not set correctly for discrimination. Problem is that after restoring the 250A device it now trips on a very small load, literally a couple of amps per phase. Wondered if anyone has seen this before? has the trip unit been destroyed by the fault or has its electronics got into a pickle?


As it was night time there was not enough load to even light the micrologic display. As a temp clear I managed to move the circuit onto an unused 100A device in the panel but for 13 flats and the communals dont know how long ill get away with that.


PS can the trip units be replaced safely on these units without isolating the upstream device, this would be a 1600A ACB feeding a very large development.


Thanks in advance


Tom

Does page 13 help at all?

Compact NSX Micrologic 5/6/7 - Electronic Trip Units - User Guide - 01/2020 (schneider-electric.com)


P.S. Internal Power Supply for Micrologic 5 and 6 Trip Units The protection functions and the test functions of Micrologic 5 and 6 trip units operate with the current through the internal current transformers (CT). When the load current is higher than 20% of the rated current In, the internal current supply provides the power supply for the full functioning of the Micrologic trip unit. This includes:  The Micrologic display screen and LEDs  The maintenance and diagnostic functions To provide a power supply to the Micrologic 5 or 6 trip unit when the load is below 20% of the rated current In, and maintain the full functioning of the Micrologic trip unit, one of the following optional power supplies can be used:  An external 24 Vdc power supply connected permanently to the Micrologic trip unit  A power supply connected temporarily to the test port on the Micrologic trip unit:  Pocket battery  PC through USB maintenance interface Each optional Micrologic power supply is described further.


P.P.S.

HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH  If the trip unit displays a St0p screen, replace the Micrologic trip unit immediately.  If trip unit displays a fault screen, do not close the circuit breaker again without first inspecting and, if necessary, repairing the downstream electrical equipment.  Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E or CSA Z462 or local equivalent.  This equipment must only be installed and serviced by qualified electrical personnel.  Turn off all power supplying this equipment before working on or inside equipment.  Always use a properly rated voltage sensing device to confirm that power is off.  Replace all devices, doors, and covers before turning on power to this equipment. Failure to follow these instructions will result in death or serious injury

Z.