Instantaneous Protection

The instantaneous-protection function protects the distribution system against solid short circuits. Contrary to the short-time protection function, the time delay for instantaneous protection is not adjustable.

The tripping order is sent to the circuit breaker as soon as current exceeds the set value, with a fixed time delay of 20 milliseconds.
This function carries out true rms measurements.
The energy reduction maintenance setting (ERMS) function is added to the instantaneous protection function by addition of an optional IO module to the IMU configured to perform the pre-defined application 3 or the ERMS user-defined application.

For more information, refer to IO Input/Output Interface for LV circuit breaker user guide.
For the factory settings, the setting ranges, increment steps and setting accuracies, refer to Threshold and Time-Delay Settings.

Instantaneous Pick-Up Ii

Pick-up (accuracy ± 10%)

Isd = In x ...

OFF

Circuit breakers have two types of instantaneous protection:

Adjustable instantaneous protection Ii
Self-protection

Depending on the circuit breaker, the OFF position corresponds to the self-protection pickup.

Energy Reduction Maintenance Settings (ERMS) Function

DANGER
HAZARD Of ARC FLASH Do not change the settings of MicroLogic P trip unit while in ERMS mode, Seal the transparent cover of the MicroLogic P trip unit when using the ERMS mode. Failure to follow these instructions will result in death or serious injury.

The energy reduction maintenance setting (ERMS) function is available on circuit breaker fitted with:

A BCM ULP with firmware version 4.1.0 and above.
A MicroLogic P trip unit:
- With firmware version Plogic-2014AN and above.
- With hardware compatible with the ERMS function. Use the customer engineering tool to check the MicroLogic hardware version, or the COM option to check that the hardware version coded in register 8709 is equal to 0x1000.

The ERMS function allows the selection of the MicroLogic trip unit settings: Normal and ERMS mode.

The ERMS function is used to reduce the Ii protection settings in order to trip as fast as possible when a fault occurs. The factory setting for Ii protection in ERMS mode is 2 x In. This protection parameter can be modified using the customer engineering tool.

If any of the basic protection settings using the rotary dial is modified on the MicroLogic trip unit while in ERMS mode, the MicroLogic trip unit switches immediately to the normal mode. The MicroLogic trip unit returns automatically to the ERMS mode after 5 seconds.

The selection of the normal or ERMS mode is made by a selector switch connected to two inputs of the IO module.

When the ERMS mode is engaged, ERMS is shown on the display of the MicroLogic trip unit and a pilot light connected to the output O3 of the IO module will be in ON state.

NOTE: ERMS may be activated after a short delay due to internal controls in the system. Ensure that the Output 3 (O3) of IO module is ON and MicroLogic HMI displays ERMS before operating the equipment.

MicroLogic display with ERMS mode engaged

The locking pad of the communication interface module (IFM or IFE ) must be in UNLOCK position (padlock open) while performing the energy reduction maintenance setting (ERMS).

The parameter Access permit in the COM setup/Remote setting menu on the display of the MicroLogic trip unit must be set to YES for IMU without IFM/IFE.

This is based on the following behavior:

IMU with IFM/IFE
- Setting Access permit parameter: The Access permit parameter can be changed only from IFM/IFE using the LOCK/UNLOCK dial.
- Behavior: ERMS ON and OFF orders are executed even if Access permit parameter is set as NO.
IMU without IFM/IFE
- Setting Access permit parameter: The Access permit parameter can be changed only from the display of the MicroLogic trip unit.
- Behavior: ERMS ON and OFF orders are not executed if Access permit parameter is set as NO.

NOTE: The ERMS ON and OFF orders are executed only when the access parameter is set to YES and the passcode in the MicroLogic trip unit must be set to 0000.

If the ERMS function or COM option is used, it is advisable to connect a second dedicated power supply to the F1-/F2+ terminals to supply the MicroLogic P trip unit.

For more information, refer to Power Supply.