Something forgotten after a long layoff

[Pete999]

An HV question, I use to be an AP (Authorised Person for several HV distributions) but having not touched it for many years, I was just mulling over things last night, and I recall, when phasing out a 11KV ring main, I seem to remember that when doing this, if you phased across 2 cores on different phases you saw 11KV on your phasing kit, yet if you phased between cores on the same phase you didn't get 0V as you would with a LV circuit, you got approximately half of the HV voltage, in the case of 11KV you would get 5.5KV, for the life of me I can't remember why this is, does anyone know the answer? for no other reason than interest.

 

[The Ghost]

Are you talking about the cube root thing? so 11kv on single is because of this i.e. 11kv/1.732 is 6.35 kv from memory, something like that?

 

[Pete999]

Are you talking about the cube root thing? so 11kv on single is because of this i.e. 11kv/1.732 is 6.35 kv from memory, something like that?

You mean square root don't you Vorti, yes it could be that but if you tested L1 to the other cable L2 you would read 11KV whereas if you tested between L1 on both cable ends you read half of 11KV for some reason, as they would both be live in a HV RMU, this wouldn't be the same if you were working with LV L1 to L2 you would get 400V and L1 to L1 would be 0V, Very difficult to explain, I'm afraid sorry I can't explain it better.

 

[Pete999]

Think I may have sussed it, HV is distributed in a Delta configuration