Hi PISCEAN 2010

can you explain in detail your SLD till the Machine end.

your SLD should contain all the ratings whatever you have.

Dear PISCEAN

Do you know the fault level at Transformer end

For example, if you are having a fault level of 50 kA means,

try to select the ABB (just in output side of transformer) also 50 kA

try to select the ABB (800 A at OLD shop) also 50 kA

try to select the ABB (800 A at OLD shop @ Power House) as 35 kA

try to select the 630A MCCB as 35 kA

Further downstreams are 20 kA, 10 kA and 6 kA so on.

it is clarified your doubt or kindly revert me.

Hello PISCEAN

pl refer my example with respect your SLD layout in PDF format.

i guided you to select according to the short circuit level co-ordination only.

normally transformer end (source end) should have higher short circuit level - since, it is driving more connected load.

individual connected load (which are there in the down stream) should have the lower short circuit protection.

For example,

      Source (50 kA)

              !

              !

  Connected load - 1 (35 kA)

              !

              !

  Connected load - 2 (20 kA)

              !

              !

  Connected load - 3 (10 kA) etc.