What happens to the voltage on a phase conductor and the neutral if a voltage surge is great enough to have a coupling effect between the two?

• A. Voltage on the phase is reduced and voltage on the neutral is increased
• B. Voltage on the phase is increased and voltage on the phase is decreased
• C. Voltage on the phase is increased and voltage on the phase is increased
• D. Voltage on the phase is reduced and voltage on the neutral is decreased

Answer: (A)

When a voltage surge couples between a phase conductor and the neutral, energy is shared between the two paths through their mutual impedance and stray capacitances. The neutral is tied to ground and has a return path that makes it more susceptible to rising in potential during the transient. As the neutral voltage climbs, the reference point for the circuit shifts upward, which reduces the voltage difference between the phase and the neutral. In other words, the phase conductor’s voltage tends to decrease while the neutral’s voltage increases during the surge, before the system returns to normal once the surge subsides.