TSD – Short Time Delay Setting

In any MCCB, the short time delay setting is the intentional time delay set so that the MCCB operates only after the set time delay, even if the actual current is more than the set current. The short time delay is set duly considering co-ordination requirements.

But, as MCCBs are generally Utilisation Category 'A' Circuit Breakers, it is not advisable to set a time delay for short circuit. MCCBs do not have a short time withstand current (Icw) rating.

I'll take it a step further. Those settings are for use in coordinated system protection shemes and by virtue of the fact that you had to ask that question, you are inherently unqualified to be doing that function. No offense, I'm just saying that this is not an issue solved by asking a question in a forum, this is something for an experienced Electrical Engineer who is doing a Coordination Plan in conjunction with ALL of your system protection devices.