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Post by colly0410 on Mar 10, 2013 16:38:28 GMT -5
I've been reading about SWER (single wire earth return) HV distribution systems. What effects (if any) would a SWER line have on electrics, communications equipment, corrosion of roof supports, safety ect if it was to pass over underground mine workings?
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Post by Wheldale on Mar 10, 2013 17:01:34 GMT -5
I might have totally mis-understood this post but I remember when studying engineering at Selby College, we had a lecturer called Pat Wilson I think his name was. He used to be an colliery electrical engineer. He was teaching us about toroidal transformers and then told us about a Yorkshire colliery he worked at were the workings were about 200 meters deep. A development heading was being driven underneath and in the same direction of a line of overhead HV cabels. He told us that the transformers were tripping out due to earth leakage. He said the rings in the heading were acting like a toroidal transformer thus creating earth leakage tripping out the switch gear.
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Post by John on Mar 11, 2013 8:52:16 GMT -5
I've been reading about SWER (single wire earth return) HV distribution systems. What effects (if any) would a SWER line have on electrics, communications equipment, corrosion of roof supports, safety ect if it was to pass over underground mine workings? |
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Post by John on Mar 11, 2013 8:54:17 GMT -5
I might have totally mis-understood this post but I remember when studying engineering at Selby College, we had a lecturer called Pat Wilson I think his name was. He used to be an colliery electrical engineer. He was teaching us about toroidal transformers and then told us about a Yorkshire colliery he worked at were the workings were about 200 meters deep. A development heading was being driven underneath and in the same direction of a line of overhead HV cabels. He told us that the transformers were tripping out due to earth leakage. He said the rings in the heading were acting like a toroidal transformer thus creating earth leakage tripping out the switch gear. |
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Post by Wheldale on Mar 11, 2013 10:08:33 GMT -5
It was 20 years ago nearly but he did like his stories! But I do remember him telling us this story and a few others! Not being an electrician I don't know if its true or not!
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Post by John on Mar 11, 2013 11:01:47 GMT -5
It was 20 years ago nearly but he did like his stories! But I do remember him telling us this story and a few others! Not being an electrician I don't know if its true or not!
Torroid's make the most efficient transformers for certain applications. Wecol made use of a toroid transformer in their E/L module used in the sensitive E/L GEB's, like the A67, A69 and P70 range.
It was always on afternoons this happened, never could grasp what was causing the problem, but was covering the mine for breakdown maintenance only prior to going to full production at Boulby Mine. There were four shift electricians including myself on this temporary arrangement.
About an hour into the shift I was getting E/L trips in all districts, no sooner had I cleared one, than another call to another trip...Oddly this never happened with the Brush transformers supplying 1100 volts to the banks of GEB's or belts, only to the Wecol GEB's in the districts.
About a week after this had started, one of the other electricians asked me if I'd been getting the same problems, seems he had cracked the root cause of all these trips.
The No1 winding engine was going through commissioning tests and it was during regenerative braking tests the problems arose, causing "spikes" on the line, that the E/L modules were interpreting as an earth fault.
On bringing this up with our Engineer, he told us he was aware of the problem and there was a static compensator being installed to "tune" out this anomaly, which should be up and working by the time full production was under way.
After about a week the problem was resolved and we soon forgot about it.
Some weeks later, control room called to notify me of a couple of E/L faults in two of the districts, then another, until I was running around resetting them..
Then a "bell" rang in my head... I called the control room, and asked them to call the process plant electricians and ask them to check whether the static compensator was in line. Turned out it had tripped out..No further problems after that. |
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Post by John on Mar 11, 2013 13:50:25 GMT -5
I've been reading about SWER (single wire earth return) HV distribution systems. What effects (if any) would a SWER line have on electrics, communications equipment, corrosion of roof supports, safety ect if it was to pass over underground mine workings?
My cousins place is fed via a high voltage line with one side of the transformer primary earthed.
I've not seen it used here in the states though, not to say it's not used.
I don't think they have too many problems other than the obvious heavy return ohmic losses against a low loss dual line return.
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Post by colly0410 on Mar 11, 2013 15:04:35 GMT -5
Never heard of SWER till I asked googe why "London underground used four rails?" It explained how using earthed running rails for return currents in urban areas caused stray ground currents in gas & water pipes & gas/water board got upset. It explained how they used a fourth (center) rail for return current to negate this & somehow it linked through to SWER. That got me thinking "if stray ground currents bugger up gas & water pipes, what effect would it have on mine workings?"
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Post by John on Mar 11, 2013 16:08:48 GMT -5
Although I doubt any, as most mines are pretty deep, but at least one ignition of gas has been attributed to lightning traveling from a ground strike and being directed through a roof bolt...
That has raised a lot of questions regarding safety underground during a lightning storm. That explosion was in the states and in a pretty deep coal mine.
It's not unknown for drift conveyors to take a direct strike, hence regulations in most countries requiring drift conveyor structures to be bonded throughout their length, and earthed to the mines earthing system at various points along the conveyors length.
Remember though, all our regulations came through accidents, some totally unseen, like the ignition caused by aluminium striking a rusty rail..
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Post by John on Mar 11, 2013 16:16:26 GMT -5
Just had a thought on the question, slightly different situation, but many years back I worked for Beeston Boiler Company as one of their nightshift maintenance electricians on the BMD automatic foundry plant.
A lot of welding took place at night when the plant was shut down.
The plant had state of the art electronic control with electronic sensors mounted all over the place, and small conveyor motors driving bogeys from the various sections.
There was a lot of problems on start up pre dayshift tests, we found cables burnt out, modules smoked and motor windings fried... Had us beat for a while until we realized the welding took place with only the electrode cable from a remote welding transformer in one of the other shops.
All grounds for welding was through all the plants steelwork..
Multiple earth returns was taking place through flexible cables, motors and control cables.
After that, the orders were ANYONE carrying out welding, must take take the earth return electrode and clamp it to the piece of work being welded..
Problem solved.
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Post by dazbt on Mar 11, 2013 16:49:14 GMT -5
I had a battery powered wireless doorbell that was actuated every time the fluorescent light in my adjacent garage was switched on.   |
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Post by colly0410 on Mar 11, 2013 17:11:44 GMT -5
I had a battery powered wireless doorbell that was actuated every time the fluorescent light in my adjacent garage was switched on. I rented a flat in Chapel-st-Leonards a few years ago & every time there was a flash of lightning it ding-donged, it drove me mad when we had night time thunderstorms.  |
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Post by colly0410 on Mar 11, 2013 17:16:24 GMT -5
I had a battery powered wireless doorbell that was actuated every time the fluorescent light in my adjacent garage was switched on. I rented a flat in Chapel-st-Leonards a few years ago & every time there was a flash of lightning it ding-donged, it drove me mad when we had night time thunderstorms. The doorbell ding-donged, not the flat. I need a new brain. |
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