Instantaneous Overcurrent Protection (I or ANSI 50)

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 B, 5.0 B, and 6.0 B 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.