Confirm the +/- values

[Knobhead]

Could someone please confirm the +/- values of voltage supply in the UK. (With a reference, now I’m pushing my luck)!

I’ve always worked on –5% to + 7.5%. the first plants I worked on were all supplied at 11400V so all transformers had the taps set at +2.5%.

I have looked and it’s like wading through porridge to get a true definition!

 

[needasparks]

Had a chat with DNO yesterday and they seem to all give different % values +/- for supply voltage.
One said 5%- and 7%+ and another said 216-258v were acceptable.

 

[Richard Burns]

Best I can find is the legislation, -6% and +10% for 230V but I thought they were due to change to +-10%.

Can't find that though.

The electricity supply regulations 1988
State:

30 (2)
For the purposes of this regulation, and unless otherwise agreed by the consumer, the permitted variations are—
(a)a variation not exceeding one per cent above or below the declared frequency; and
(b)a variation not exceeding six per cent above or below the declared voltage at that frequency where that voltage is below 132 kV, and not exceeding 10 per cent above or below the declared voltage where that voltage is 132 kV or above,
or the variation which may have been authorised by the Secretary of State under paragraph (3).

This was amended in 1994 to read:
(2) For the purposes of this regulation, unless otherwise agreed by the consumer, the permitted variations are:
(a)a variation not exceeding one per cent above or below the declared frequency;
(b)in the case of a low voltage supply, a variation not exceeding ten per cent above or six per cent below the declared voltage at the declared frequency;
(c)in the case of a high voltage supply operating at a voltage below 132 kV, a variation not exceeding six per cent above or below the declared voltage at the declared frequency; and
(d)in the case of a high voltage supply operating at a voltage of 132 kV or above, a variation not exceeding ten per cent above or below the declared voltage at the declared frequency.”

 

[telectrix]

as i understand it, it was always +/- 6%, then the +10% was introduced so that we could use 240V and call it 230V

 

[MarkieSparkie]

Best I can find is the legislation, -6% and +10% for 230V but I thought they were due to change to +-10%.

Can't find that though. ...

A second round of harmonisation with a change in the declared nominal supply voltage (Cenelec HD472-S2) of 230V +-10% is pending, it was due on 1/1/2008 but has yet to be implemented in the UK.

 

[Chr!s]

ESQCR, 27



Low voltage + 10% - 6% (Nominal 230V)

High voltage less than 132,000 + - 6%

High voltage Equal> 132,000 + - 10%

 

[UNG]

A second round of harmonisation with a change in the declared nominal supply voltage (Cenelec HD472-S2) of 230V +-10% is pending, it was due on 1/1/2008 but has yet to be implemented in the UK.

Talking to a guy from Scottish Power just before christmas the powers that be are looking resurrect the 230v +/- 10% harmonisation but he had no idea on when it might be implemented

 

[Knobhead]

My reason for asking is due to a phone call from an old colleague. He’s got the back-lash from a fault I had years back and it’s reared it’s head again with the same consequences. VSD’s going up in smoke over a weekend when a plant is shut down. The fault was when I looked at it all that time back was the O/L for the 33/11KV 20MVA transformer On Load Tap Changer motor had tripped. So as the grid supply voltage raised at the weekend the OLTC didn’t compensate. He found the same. The stupid thing is the alarm and protection panels had lights for everything baring O/L trip!

Now there are complaints from outside consumers fed by this private network.

It was a weird set up. The grid fed 132KV to a local sub where it was stepped down to 33KV via two 60MVA transformers. These fed in to the 33KV local grid and our four 20MVA 33/11KV transformers. The voltage regulation is done at the 33/11KV level. So it was possible to have 4 different voltages on the same plant as each OLTC worked independent of each other. Everywhere else I’ve worked the OLTC’s would work in Leader/Follower mode, so if the leader changed the others would follow giving an equal voltage.

Each voltage regulator has these settings
1/ Independent manual
2/ Independent auto
3/ Leader (auto)
4/ Follower

 

[needasparks]

All sounds about right. None of the energy suppliers know then and all say different things.

 

[Bobster]

The site I work in has just had a very similar problem Tony. Re energising from a shut down (no major load yet) a set of oxygen analysers hadn't been isolated correctly there circuitry went up in smoke as 460v to line to line through them. We don't have auto tapping transformers, not a problem when sites up and running, but the 10% of the year its not we have to be specific with what we use and where.