We had a number of stations that were at 500KV. The devices in the second photo look like capacitive coupling potential devices CCPD. They are used to give a highly reduced sample of the power line potential that could be safely used in the substation for metering and fault detection. The meters on a 500KV line would read on the 0 to 5 volt scale. This voltage along with a current sample from current transformers which are coils around the bushings like donuts. You measure the potential, current, and the phase angle between them to give the reading on the line. We had relays that were set to trip when the current got too high at a test voltage. We used the old I lag E vector analysis. The last I saw of this work was in 1993, and we calculated with a simple scientific calculator. They probably have computer programs the engineers run on laptops to test everything now.
More information than you wanted to read, and less interesting than Lee's story, but it paid the bills. 
