Just before all the self isolation and not being closer than 6 foot to anyone else I had a chat with a couple of DNO engineers who were doing insulation tests on the HV cables going to/from a sustation at the end of the road the 11Kv cables are tested at 15 Kv to Earth not sure if they used AC or DC. Another thing was the that I never realised just how big the fuse holders for the outgoing LV cables are I asked what size the fuses were and they told me they were 400 amps. I was just being nosey but it's interesting to me to see just where my juice comes from which is a rather scruffy 500 KVA transformer
The cable testing would use DC. AC is not suitable because there is no simple way to tell the difference between most undesirable leakage, and entirely normal capacitive coupling.
Leakage of say 10ma at 11KV is serious as it may indicate imminent breakdown. A capacitive charging current of 10ma or more is normal according to the length of the cable.
Thanks Broadgage and Harry one of the engineers said the leakage was down in the micro amps range which is good I can see that the tiny leakage would be swamped by the capacitive charging current especially on a longer line. Now can I say that I know that at times I seem to be a bit over curiouse about certain things the truth Is i have that sort of personality I didn't want to be this way I just am. I have always struggled in social situations things that other people deal with easily are a real minefeild for me social conventions really are a struggle at times. When I was a teenager I would read lots of books and found I enjoyed learning and that radio and electricity seemed easier to understand I suppose they just came naturally to me. Reading was my escape I was bullied at school and at work which just re enforced my fear of people. Any how I just wanted to say all this hope you guys can understand what I mean thanks for getting this far regards Kelly
The cable testing would use DC. AC is not suitable because there is no simple way to tell the difference between most undesirable leakage, and entirely normal capacitive coupling.
Leakage of say 10ma at 11KV is serious as it may indicate imminent breakdown. A capacitive charging current of 10ma or more is normal according to the length of the cable.
Selecting the DC test voltage is important on XLPE Cables designed to operate on AC.
Typically, you probably don't want to be much above 5kV if you want to avoid irreparable damage within the XLPE - it causes cracks or so called "trees" within the insulation.
If it has to be tested above that 5kV limit level, then better to use very low frequency (VLF) AC testing
" I have always struggled in social situations things that other people deal with easily". Sounds like a touch of Aspergers to me, but don't worry, you would be in good company.
Simon Baron-Cohen, who writes books on these things says he plays a game at Cambridge University, spot the Aspergers, only in the Electrical Engineering Dept, he plays it the other way round, try to spot the ones who aren't Aspi.
I have to admit my girlfriend did suggest I had aspergers or possible a low order of autism I dismissed it out of hand thinking that I needed another label like I need a hole in the head but now I see I probably have got one or the other it's a hard thing to accept but hay ho il get there
I have to admit my girlfriend did suggest I had aspergers or possible a low order of autism I dismissed it out of hand thinking that I needed another label like I need a hole in the head but now I see I probably have got one or the other it's a hard thing to accept but hay ho il get there
