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I am wondering how long the customers were without power as it would take some time to replace the burnt out items.

Andy
 
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I am wondering how long the customers were without power as it would take some time to replace the burnt out items.
Indeed - interesting question, particularly given that I imagine that those outgoing cables disappearing into the floor will probably have been damaged ... unless, of course, there were some place further downstream where consumers could have been switched to a different source of supply.

It's a tribute to the systems/infrastructure and the DNO guys that service interruptions are often remarkably short even in the face of what appear to be pretty horrendous equipment failures.

Kind Regards, John
 
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Customers lost supply around 0830 and were back 1230 the same day......the FOUR incoming cables all had backfeeds so they were just "POT-ENDED" outside the substation. ie a LIVE end.

Many hundreds of SP subs are very similar to this one, with open LV distribution boards. There are very little accidents. and as Westie says we have a very strict LIVE WORKING POLICY to follow and adhere too.

The Dials on the left hand side are,were MAX DEMAND INDICATORS, that if indeed a Transformer had been connected to the board they would indicate the current the Transformer was importing into the board and also another needle would indicate the MAX current that had been exported......They usually have a 20 min time lag.

The equipment above the dials is a ACB (Air Circuit Breaker) that, agaon should a transformer be connected the connection between the transformer and the did board can be electrically/manually tripped. Usually fitted to interconnected substations so that an HV fault cannot be back-fed by the LV network.
 
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MDI Max Demand Indicator.....The red needle is the MAX and the black is current loading around 20 mins ago



ACB Air Circuit Breaker .....electrically and manually trippable circuit breaker.....this one has the common "asbestos!!" arc interuptors and is operated by a 30v DC supply via any of several relays....these can be fun when switched OFF , you see the lights DIP nice and low ie. WAY out of supply regs, and then the buggers wont close back up again.....

 
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We used to have a 12 pulse DC motor which was thyristor driven.
The drive was fed with six phases from a phase shift transformer - one set of three output in star, one set output in delta. 30 deg. shift between the two sets of outputs.
This created a smoother 'DC' waveform and less noise on the s.upply
 
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Back in the 1970's I came across a 5 phase supply from a motor generator set. From memory it was 280 volts and 200 (?) Hz. It powered high speed saws in a furniture factory.
 
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... six phases from a phase shift transformer - one set of three output in star, one set output in delta. 30 deg. shift between the two sets of outputs.
I definitely need to think about that - maybe the thinking will become easier after I have opened a bottle :)

Kind Regards, John
 

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