Amtech Showing Error in Selectivity Study: The disconnection time of the Upstream Earth fault Protection is Lower than that For this Circuit. If1 90A and If2 153A. How we can resolve this kind of error in Amtech.

Well first of all, it may be desired behaviour - sometimes you do want this.

A really simple example would be one RCD in the supply to a few MCBs. The MCBs catch overloads and each disconnects one circuit, the RCD catches earth faults and removes power to all of them.

But assuming you have done this by mistake, then you need to place your earth fault detection downstream of your overload protection so an earth fault only disconnects part of the system.

So what is your circuit doing, and what disconnection sequence are you actually hoping for for different fault conditions. (not using Amtech at this point, just a description of the design in words.)

Mike.

Well first of all, it may be desired behaviour - sometimes you do want this.

A really simple example would be one RCD in the supply to a few MCBs. The MCBs catch overloads and each disconnects one circuit, the RCD catches earth faults and removes power to all of them.

But assuming you have done this by mistake, then you need to place your earth fault detection downstream of your overload protection so an earth fault only disconnects part of the system.

So what is your circuit doing, and what disconnection sequence are you actually hoping for for different fault conditions. (not using Amtech at this point, just a description of the design in words.)

Mike.