Fault Loop Impedance Calculation ✰

However, the single-phase earth fault loop impedance ($Z_s$) remains the most critical for shock protection.

Earth fault loop impedance is the total resistance encountered by a fault current flowing from a point of failure back to the transformer. fault loop impedance calculation

Resistance increases with heat. Cables under load get hot. When calculating for fault conditions, we must correct the resistance to the operating temperature (e.g., $70^\circ C$ for thermoplastic cable). However, the single-phase earth fault loop impedance ($Z_s$)

(R1+R2)=(Table Value×Length×Ambient Temp Correction Factor)1000open paren cap R sub 1 plus cap R sub 2 close paren equals the fraction with numerator open paren Table Value cross Length cross Ambient Temp Correction Factor close paren and denominator 1000 end-fraction Step 3: Account for Temperature ( Ctrcap C sub t r end-sub fault loop impedance calculation