Surge arrester may protect the distribution system against excessive overvoltage imposed in the system that could damage the electrical apparatus connected to the line and avoid blackouts and replacement of the affected components such as distribution transformer, line insulation, and others.
Does the 2400V delta system include any Earthing transformer?
If not, an unearthed system poses challenge in identifying / isolating the faulty feeder in case of SLG fault (Single Line to Ground fault).
Uncleared SLG fault means higher voltage to ground on the two healthy phases (L-G voltage equal to L-L voltage).
If the higher voltage is allowed to remain for extended periods, it could harm the system.
This is where the Surge Arresters play a role in a Delta distribution system.
Surge arresters are not designed to limit power system voltages. Arresters on a delta system have to have MCOV ratings above the Ø-Ø voltage. If not, they could be destroyed by the overvoltage during an uncleared SLG fault.
I suppose the Surge arresters can protect the system against arcing grounds associated with ungrounded systems. Arcing grounds can cause healthy phase voltage to rise 4-5 times the rated.
The conventional phase-to-ground connections of three surge arresters may not provide the optimal surge protection. For those cases, surge arrester protection between phases is recommended particularly for transformer windings in delta-connection. For details see the sketches below.
