Power System Generation, Transmission and Distribution

A: Solid grounding would drive several kA through a stator core fault and turn a minor insulation issue into scrap iron, an ungrounded neutral allows transient overvoltages that age insulation and mask single-line-to-ground faults, a low-resistance reactor is used where high ground fault current is acceptable for protection speed, and high-resistance grounding limits fault current while still allowing sensitive ground fault detection on unit-connected machines.

A: A 0.3 MW loss would correspond to currents under 100 A and contradict the P=√3VI relation, 3 MW drops one phase from the I²R sum, summing I²R for three phases at roughly 800 A each gives on the order of 6 MW per 100 km, and 15 MW assumes either doubled resistance or much lower voltage than stated.

A: CT polarity errors distort measurements without killing reactive injection, harmonic resonance tends to overcurrent healthy phases rather than drive one to zero, an internally fused capacitor can silently isolate a phase and reduce kvar with minimal protection response, and SCADA loss only blinds the operator rather than altering electrical behavior.

A: 3.8 kA ignores the three-phase relationship, 7.6 kA mixes up line and phase quantities, applying I = 250 / (√3 × 11) lands near 13 kA, and 22 kA only makes sense if the assumed fault level were much higher.