What is the meaning of I2t ON (Max resettable time) and I2t OFF (Max break time) of Shot-time protection of Micrologic 2.0A/E, 5.0A/E, 6.0A/E and 7.0A

Short-time protection

-  The short-time protection function protects the distribution system against impedant short-circuits.
-  The short-time tripping delay can be used to ensure discrimination with a downstream circuit breaker.
-  This function carries out true rms measurements.
-  The I2t ON and I2t OFF options enhance discrimination with downstream protection devices.
-  Use of I2t curves with short-time protection:
-  I2t OFF selected: the protection function implements a constant time curve;
-  I2t ON selected: the protection function implements an I2t inverse-time curve up to 10 Ir. Above 10 Ir, the time curve is constant.
-  Zone selective interlocking (ZSI).

The short-time and ground-fault protection functions enable time discrimination
by delaying the upstream devices to provide the downstream devices the time required to clear the fault. Zone selective interlocking can be used to obtain total discrimination between circuit breakers using external wiring.


Max resettable and max break times are the times linked to instantaneous protection.

> Max resettable time is the time the breaker could withstand a fault before giving a tripping order.
It means Max resettable time is the time during which a FAULT can appear, before the trip of the Circuit Breaker.

> Max break time is the maximum time for the Circuit breaker and the Micrologic to eliminate the fault.
It means Max break time it is the tripping time max including the global tripping chain of the circuit breaker.

Released for:Schneider Electric Thailand