What is the purpose of a configuration like this?
MannyL
Basically, a crew is working on a portion of the line and they cut in a couple of sets of isolators to establish a clearance point. Between the isolators they ran a temporary ground. The ground is there to trip the breaker if the isolators track over.
Ok it would make sense that they want all the lines to have a common ground for some reason but it’s been like that for a few years.
Well, i didn’t say they were working fast…
In reality, there may be many reasons that this arrangement may be up for years. There may be a road-widening job that has been put on hold which will require relocating a pole. They may not need that section of line anymore but want to maintain their easement. There may be non-utility workers operating cranes, loaders, dump trucks or what-have-you in proximity to the overhead conductors and the utility thought it best to de-energize the line for the duration of such work instead of tying up one of their employees as a spotter.
You could follow the line to see if any of these conditions obtain, should your curiosity get the best of you, i may be entirely off base. Still, as i said, there may be any number of reasons.
The point is not that the lines have a common ground, just that they have a ground (in his case, the phases are tied to the system neutral). My best guess is that they put the grounds between two sets of isolators as an additional level of protection. If the isolators track over, the ground will cause a fault, operating the circuit breaker back at the substation, de-energizing the entire circuit. The second set of isolators will prevent this ‘leakage’ from energizing the non-grounded portion of the line for the brief time it takes the circuit breaker to operate.