Hi flint !!!

sorry for the delayed reply.Well bck 2 topic,
Yes, U r partially right. DB main breaker is 10kA rating and its branches will be 6kA. Where SDP with MCCB, 36kA rating and MDB ll have MCCB or ACB , 50kA rating. Upto this u r rite.

consider the fact, all the loads wont be connected. pls remember concept of Demand factor. According NEC tables D.F value for SDP (10 DB`s Connected) ll be 0.4 to 0.5. hence the incoming breaker for SDP = 100A(wont be 100A at all, lets consider for the calculation) x 10( no. of DB`s) x 0.4 = 400A.

For MDB level, Demand factor ll be reduced to 0.3 to 04, rating ll be

10(No. of. SDP`s) x 10(No. of. DB`s) x 100A x 0.3 = 3000A. from this we can easily size the transformer or Generator.

Hope u can under stand this calculation.

Dear Flint, i m just looking for some proper calculation for this kA ratings. if any like that, please share with me.

ThX n Advance,


if something wrong pls correct me..