The 11kv ring is rarely closed but run with a deliberate open circuit to li mit fault levels.thus points are fed from one end or the other. If a sectio n suffers damage or requires operational intervention it can be switched ou t and the remainder of the system can continue to operate by selective swit ching.
when I worked for SESEB in the early 1960s, 11kV was a real ring
11KV here is a real ring
Not here. The distribution looks like a collection of rings but strategically placed air switches that would create actual rings, if closed, are left open. When there is a fault these (NO or NC) switches can be opened/closed to isolate the fault and get customers on unaffected sections of line back on supply quickly. Once the fault has been cleared and the affected line re-energised there might be a short period of time when true rings exist but only until the NO switches are opened.
There are also implications with rings and auto-reclosers. If one auto-recloser trips, it's "dead" side will still be live via the auto-recloser feeding the other end of the ring. Which knocks onto to loading, with one auto-recloser tripped all the load on the (ex) ring is fed via that single line, re-closer and overload protection.
Current in pylons, hopefully none. In the cables between them, I've watched an ammeter monitoring one of the 125 kV lines feeding Cardiff. The needle was gently waving by about 10 A centred on 100 A ish. That's only 12.5 MW. I think the 500 kV lines can carry a GW or more, thats 2000 A +.
Or its struck by lightning as I had the misfortune to be standing near one when it was. It was bleedin loud. No damage done though. I think this is one reason they have that extra cable across the top. However I think this post must have been from a bot. Brian
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