What is the concern about sustained overvoltages?
Sustained abnormal overvoltages of the utility distribution system can exceed the surge protective device’s (SPDs) Maximum Continuous Operating Voltage or MCOV. If this happens, the SPDs non-linear clamping elements will begin to clamp on the crest of the utility voltage (120 times a second on 60Hz systems).
TOP Are underground cables protected from lightning? Underground cables offer greater isolation to the effects of lightning when compared to aerial cables, however they are still subject to induced electromagnetic coupling of energy from nearby ground flashes. As such, surge protection should be installed on facilities supplied by both, overhead and underground, power feeders. TOP Grounding & Surge Protection What is Ground Potential Rise (GPR)? When a large amount of energy is rapidly deposited into the ground by a cloud-to-ground lightning strike or by an electrical fault on a utility power system, the ground potential at this injection point rises to a higher level with respect to the more distant ground. This has the effect of creating a voltage potential gradient in the earth, which can cause dangerous touch and step potentials to personnel exist. By creating an equi-potential ground plane beneath a facility by electrically bonding all separate grounds into a system or by burying
