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Current Split Factor Sf

Current Split Factor Sf

Current Split Factor Sf

(OP)
I am trying to determine the current split factor Sf using of a  network having an utility of 400MVA, X/R=7 connected to Bus-1 of 69 KV and a transformer T1 of 5MVA with R%=0.38, X%=5.73. Secondary of T-1 is connected to Bus-2 of 13.8KV in which a generator 5MVA with Xd"=0.10 X/R=30 and a transformer T-2 of 1MVA with R%=0.98, X%=5.92 are connected. The secondary T-2 connected to Bus-3 of 480V with an IM of 750hp, Xd"=0.25 X/R=320. After the fault, the direction of fault current is towards the utility from the other Buses.
I am having hard time to use the graph (Annex-C in IEEE std-80 2000) to determine the current Split factor (such as 100% remote, 75% remote & 25% local). Can anyone help me to understand how to determine the current split factor using graph for the network I'm using. Thanks for your help.
 

RE: Current Split Factor Sf

b1kpnt74,

For curiosity,what is the connection of your 5 MVA transformer?I presume that it is YNd1 where 69 kV side is WYE grounded.Also you need to know the grounding methods of 1 MVA transformer and the 5 MVA generator.

1)First you have to do a complete GF calculation mainly at the point of common coupling (PCC) at 69 kV.
2)Calculate how much is the Utility contribution for a GF at PCC.
3)Calculate how much is the percentage current contribution from your local generator for a GF at PCC.
3)Find out how many distribution and transmission lines radiating from your 69 kV PCC.
4)Obtain the grounding impedances of each such line(s).
Now depending on the percentage contributions of local (your gen) and remote (Utility),use the corresponding curve from C17 to C22 and determine the split factor.
 

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