Fault Level for Distribution Board

If the vendor documents are 20kA for 1 sec and the requirements are 10kA for 1 sec, then the board is compliant with the requirements.

Thanks Alot

from the name i understand you are an engineer of six month course. Also understand that naturally you dont know about fault level.

Dear Ahmed

You wrote "For distribution board the REQUIRED fault level 10 kA for 1 sec.".

First - Fault level is NEVER A REQUIREMENT. It comes into picture due to capacity of source, connecting cables etc. Hence all components which see this fault level, have to be designed to withstand the given fault level. Anything higher is always acceptable.

Thanks and regards

Ashok Toshniwal, Bangalore, India.

PS - There are ladies too, on this forum.

Thanks Alot

That is what I need to know

If the upstream substation 66/11 KV has 25KA for 3 second withstand rating at 11 KV side, then is it required the down stream substation 11/.4KV also required 25KA for 3 secods??

Power rating & Percentage impedance of downstream transformer will decide the short circuit current & accordingly downstream short circuit withstanding capacity is decided. For example, if downstream transformer has 4% impedance then secondary short circuit current will be 25 times the name plate current & therefore short circuit withstand capacity should be decided accordingly. This is after neglecting impedance drop in transformer & assuming short circuit takes place directly at transformer terminals, otherwise resistance of connecting cables will add to the transformer impedance & therefore reduce the short circuit current.

Thanks and regards

Ashok Toshniwal, Bangalore, India.

PS - Pls. also introduce yourself.

If the consultant or buyer specifies 10kA for 1sec it becomes the requirement to satify site conditions