Instantaneous Overcurrent Protection - ComPacT NS MicroLogic Trip Unit

Presentation

Instantaneous protection helps to protect equipment against phase-to-phase, phase-to-neutral and phase-to-ground short circuits. The protection operates with a definite time characteristic. It trips without additional time delay as soon as the setting current is exceeded.

Availability

Instantaneous overcurrent protection is available on:

MicroLogic 2.0, 5.0, and 6.0 trip units
3-pole and 4-pole circuit breakers

It is powered by the current flowing through the internal current transformers of the circuit breaker and it does not require an additional external power supply.

Operating Principle

The instantaneous overcurrent protection pickup sets the level of short-circuit current at which the circuit breaker trips with no intentional time delay.

Instantaneous overcurrent protection overrides short-time overcurrent protection when the instantaneous overcurrent pickup is adjusted to the same or a lower setting than the short-time overcurrent pickup.

Setting Instantaneous Protection for MicroLogic 2.0

The instantaneous protection pickup Isd is set by using the Ir and Isd multi-position dials on the front face of the MicroLogic trip unit.

The setting value is expressed in multiples of Ir.

Set the long-time protection first. The setting pickup is Ir.
Turn the Isd multi-position dial to the value required.
Isd = Isd setting x Ir.

The Isd setting values are: 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10.

Accuracy: +/-10 %

NOTE: The tripping time cannot be adjusted. The tripping time characteristics are:

Maximum resettable time: 20 ms
Maximum break time: 80 ms

Setting Instantaneous Protection for MicroLogic 5.0 and 6.0

The instantaneous protection pickup Ii is set by using the Ii multi-position dial on the front face of the MicroLogic trip unit.

The setting value is expressed in multiples of In.

Turn the Ii multi-position dial to the value required.
Ii = Ii setting x In.

The Ii setting values are: 2, 3, 4, 5, 6, 8, 10, 12, 15 and off.

Accuracy: +/-10 %

The off setting disables the instantaneous overcurrent protection.

NOTE: The tripping time cannot be adjusted. The tripping time characteristics are:

Maximum resettable time: 20 ms
Maximum break time: 80 ms