200 volts DC leccy in the Meadows.


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AC doesn't always throw you off either, as a young electrical apprentice I was feeding a bare wire to behind a live leg of a 440 volt 3 phase board, it caught a phase and I was unable to let go...It was only my weight as I was passing out that freed me..

I've had DC too on a contactor circuit when I was doing something illegal, fault finding underground, that was about 250 volts and very painful..Gggh!

Oooh!

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Phew what........i should cocoa..............

Hi mick2me I'll get my dad to reply to that one he should be getting up around now I think they are about 8 hrs behind us in Vancouver

Ah yes Miss Slack, she taught me to read in one year, I couldn't read up till then because of my disrupted schooling with all the moving around I did. I got a prize for progress at the end of the year

Slight digression. Tuning the klystron in a Vulcan doppler radar we had a special long (12in) copper bladed screwdriver. The copper being non-ferous was not attracted to the magnetron. If we inadvertently used a normal screwdriver, then as one gingerly probed down into the guts of the radar, it would suddenly shoot sideways on to the 8KV magnetron power supply, and the person would find themselves on the other side of the room. Still have a scar on my right arm to show that I once used the wrong screwdriver. Getting at least one EHT zap was almost a rite of passage to becoming an RAF trained avionics engineer in the early sixties.

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Even these days, electronics engineers, RF that is, still handle high voltages Alison, lots of TV and Radio stations have vacuum tube RF amplifiers with 4000 volt upwards plate voltages!

They have to have interlocks on the cabinet doors to them, but those big HV Capacitors still hold a charge that can cause problems.

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Had many small shocks in my time but only one bad one that I remember.

We were fitting central heating along Melbourne Road back in the mid 70s. I had disconnected the immersion heater and was removing the copper hot water cylinder when my arm caught the immersion switch whilst the bare end was touching the cylinder. I ended up the other side of the bedroom and had white blisters up my arms to show what a prat I had been.

Eventually picked myself up and went downstairs to remove the fuse, that's when I found it had been made good with a 1 1/2" brad.

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  • 1 year later...

Been discussing DC mains on a vintage TV/radio forum. Turns out London had both AC & DC mains at voltages of from 100 to 250 volts, also some AC supplies were at different frequencies, 25 hertz seemed to be quite common. Must have been a nightmare buying electrical stuff back then.... Also some areas of USA & Canada was on 25 hertz & some of California was on 50 hertz, that must have caused a few problems as well..

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Everything is standardized in the states now Steve, household supplies are 120-0-120, there is a 220v 3 phase system for small workshops etc, but 415 3 phase is standard, all at 60hz.

We get our supply at 7400volts single phase to the pole transformer, as it's rural and some of the runs are long, it's common to see an auto transformer to maintain the voltage plus or minus 10%. Downside to those is the current is reduced too, you can't have something for nothing.

Highest voltage circuits I was authorised to work on was 11Kv, I was authorised to enter the main switch room on the surface and could enter the 66Kv switchyard, I was issued the keys to both, but warned to stay on the marked path in the yard and NEVER stray from it unless the supply had been isolated.

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Wonder where the converter station was for the 200 V DC supply in the medders?

Near the cremourn pub?

This could answer a question which Smiffy49 was asking. Starting at post #42 here http://nottstalgia.com/forums/index.php?showtopic=12896&hl=toll&page=3

We never decided what the building was, but here's another photo of it.

power_1.jpg

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Early 60s there was still some DC on Derby road. The RC Cathedral had a big organ motor that was DC powered. The city wanted to do away with the DC for that purpose and if I remember rightly there was a bit of a dispute between the RC authorities and the city over who would have to pay for the new AC motor which would be required. Not sure how it came out. I was only an apprentice tea masher at the time.

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AFAIK the UK has the highest mains voltage at 240 volts in the world, although it's now listed at 230 volts with -6%/+10% tolerance so we can carry on on 240 volts. Wonder how many Americans plug their gubbins in over here & blow it up not knowing the voltage is twice as much?

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Different plug configuration Steve, we have 240 volts here, our own service is 120-0-120, I still have a few 240 volt power tools that I brought from Australia with me. My big 5HP compressor, bought in Sacramento, is 240 volts.

When I was a humble NCB apprentice, all portable power tools had to be 110 max voltage to comply with the M&Q Act.

My generator that runs on the tractors PTO shaft has 120-0-120 output, with one 50 amp 240 volt outlet, and several 120 volt outlets.

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When I went to America I bought some adapter plugs for the dual voltage kettle & hairdryer, the radio I took was battery so no probs there. Noticed the cooker in our apartment was 240 volts, the sockets were all 120 volts. The TV, toaster & my adapters didn't have an earth pin on them, plus there was a socket near the bath which I was surprised at. I understand the 240 volts in USA is 120 volts to earth with a centre tapped neutral supply transformer' very clever me thinks..

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Clothes driers and stoves have a very large 240 volt outlet Steve, all other outlets in houses are 120 volt, any outlet within 8 feet of a water tap, shower or bath has to be a GFI type, (Ground Fault Interrupt). I fitted a 240v 30amp 15 amp outlet in the office for a HF amplifier for my ham gear. I'll also be fitting several 15 and 30 amp 240v outlets in the workshop.

My service is 120-0-120v 200amps.

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I guess the North American system is really just a throwback to the old Edison three wire system.

I still prefer the British two wire system myself. You know where you are with it. If the neutral goes AWOL on the three wire system all kinds of funny and potentially dangerous effects take place.

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The Australian system is similar to the UK's, different plug style though, there's are rated 10 amps.

I dislike the quick connect in wiring outlets here in the states, I'd bet my boots that many fires have been caused by that stupid connector when the spring starts to get weak due to heat from overloads. I always use the screw connections.

I've seen outlets burned up and it's obvious it was caused by the use of the quick connect.

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If the neutral went awol on a 120-0-120V system then the gubbins connected to the two legs would be in series, OK if both legs were drawing the same power but not very likely. Is there a safety device to cut the juice if this happens?

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Depends where you lost the neutral, if the utility lost the neutral, the transformer would be open circuit on the HV side, no way I could lose a neutral on the sec side of the transformer, unless the transformer had a fault.

I have three heavy gauge cables I installed between the service breaker and my breaker box, it's grounded at each end too, lightning protection.

The utility provides me with a transformer mounted at the top of a power pole, it's fed by 7400 volts and transforms down to 120-0-120, the neutral is grounded together with the utilities neutral, which is also grounded at every pole to provide a low impedance to ground in the event of a fault or lightning strike.

But saying that, if my neutral for some odd reason went open circuit, no 120 outlet would work, only the live side would be just that live and no appliance would work.

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I actually got called to a house where the neutral was open back in my contracting days. The owner was complaining that some lights got brighter etc. when he plugged in a kettle. I don't remember all the details now it was some 30 odd years ago. The neutral had corroded away and burnt off in the meter socket. Maybe they'd had a lightning strike at some time, I don't know, but every outlet connects back to the neutral bar so essentially everything becomes in series with everything else. As the neutral only carries the difference High current low resistance items in series with things like a lamp would allow a higher voltage at the outlet feeding the lamp. Really bright lights!!!

If I remember rightly some clot had taken the ground clamp off the water pipe too so no route to ground. Install new meter socket and re-do the ground and all was o-k again.

I'm with you on those quick connects, John. They have been responsible for fires in outlets even when nothing was connected, especially if next to bedding or drapes. I suppose they were supposed to speed things up. More money in the pockets of contractors, but not worth it if the house burns down. Some idiots were even using them with aluminum wire, an absolute no-no. Aluminum wire presented a whole bunch of problems too in the small sizes. In the bigger sizes we used a sort of grease called Noalox to prevent the oxidization that was causing issues.

Edited to add: With respect, John. I think if the neutral is missing at the neutral bar in the panel Every circuit in the house is effectively in series with other circuits with a total of 240 volts across the two hot lines. If you have a good ground things might not be too noticeable, but with a none existent ground as I experienced voltage could be all over the map depending on the varying resistance of items plugged in.

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