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SLG Current Calculations


When PTW calculates the SLG current in bus SWBD, the following equations are used for these 2 cases:

Case1 (utility is in transformer primary side)
Isc1 = V0/(Z1+Z2+Z0)
Z1 = Zcable1 + Ztranformer1 + Zutility1
Z2 = Zcable2 + Ztranformer2 + Zutility2
Z0 = Zcable0 + Ztranformer0

Case2 (utility is in transformer secondary side)
Isc2 = V0/(Z1+Z2+Z0)
Z1 = Zcable1 + Zutility1
Z2 = Zcable2 + Zutility2
Z0 = Zcable0 + (Zutility0 || Ztranformer0)
Isc1 and Isc2 are totally different.