What purpose does the round (third) prong serve on an electrical plug?

Transmission and distribution system grounding will impact power quality. In the absence of low impedance grounds, lighting strikes will cause flashovers and momentary operations on the system. This will decrease both quality and reliability.

There are clamp on ground resistance checking devices that make the inspection of system grounds easier and far less time consuming than in the past.

Transmission grounds should be checked on a regular basis, particularly in areas with high lightning activity. Distribution grounds can be inspected less frequently but should be examined whenever work is being done on conductors, transformers or switchgear near them.