What is Arcing ground?

Answer: Arcing ground is a surge which is produced if the neutral is not connected to the earth. In three phase transmission line each phase has capacitance with respect to the earth. When an earth fault occur on any phasr, a capacitive fault current flow into the earth. Such a current if exceeds 4 – 5 ampere is sufficient to maintain an Arc in the ionized path of the fault even though the medium causing the fault has cleared itself. The presidency of the earth due to the flow of capacitance current gives rise to a condition known as arcing ground in which cyclic charging and discharging of system capacity through the fault results in high frequency oscillations being superimposed on the whole system and a build up of every high voltage can occur.

Arcing Grounds is a phenomenon which is observed in ungrounded three phase systems. In ungrounded three phase systems operating in a healthy balanced conditions, capacitances are formed between the conductors and ground. The voltage across these capacitances is the phase voltage.