@vinothkumar asaithambi said:

Hi Guys! i have the basic knowledge about LT Switch Boards & Control Panels. But i want to know about KA rating in selecting the Breakers & Panel Sizing, Can you provide me a piece of idea on this???

Hey bro,

So here is the deal, Breaking capacity is totally decided by the type of usage/type of industry . Suppose u came up wid load list….may be , lets say 800 Amps for all the feeders for an industry… u select an ACB of 1000 A or may be 1250 A , for safety purpose. Done…… now where does “Breaking capacity” come from?? From here ….
1. Humidity
2. Fault tolerance parameter
3 load impedance
4 load voltage.

so from some ground rules we compile them all and find out the breaking capacity.

It’s is denoted by kA….so when the fault occurs the amperage of a system can go up to 100 kA=100,000 A , this is huge trust me !!….sometimes 250,000.

so as to safeguard your motors ( from smallest 0.37kW to 150 kW bigger…or may be biggest) this 100kA has to be stopped from killing the motors……..we have to kill this huge current. We do it this way, selection of ACB/MCCB accordingly and also…. we gotta select the time for which the system shall cud quench fault

Generally its 50kA or 65 kA

Lot more to tell….keep askin