LV over volts amd realistic upper voltage limit from the DNO?

[UKMeterman]

Hi,
I have just moved into a house where the voltage measured on my Megger PDA1 and a RMS volt meter is often 255V or more and has sometimes reached 261 overnight. The PDA1 had also reported a large number of HF noise events of about 2volts for several mins at a time. There have been a couple of surges up to 260V. Supply is TT I am next to the HV transformer and there is a very long LV main fed from this transformer. How should I approach this with the DNO, and what would be a sensiable upper limit, I do know the letter of the law is 253 volts.

Thanks

 

[IQ Electrical]

You need to show that the tolerances and time intervals in BS 50160 are being broken and to this effect, you'll probably need a power quality report set against the paramaters of BS 50160.

About 65% of our power quality reports show a good deal of overvoltage and it's very difficult to get the DNO to take action.

Here are the parameters:

 

[UKMeterman]

Hi,
Thanks for the link, I couldn't open it but I also found the same information here, Looks like I need to get a few days reports from the PDA1 and see what period it is at 254V. I may also give the DNO a call, they recently replaced the LV transformer they may have put me on the wrong tap.

 

[IQ Electrical]

Hi,
Thanks for the link, I couldn't open it but I also found the same information here, Looks like I need to get a few days reports from the PDA1 and see what period it is at 254V. I may also give the DNO a call, they recently replaced the LV transformer they may have put me on the wrong tap.

It's possible that you're on the wrong tap but for the DNO, it's a tough balancing act to meet tolerances along the distribution circuit, that's often why they are so reluctant to drop the tap.

 

[UKMeterman]

Well,
I called the DNO at 18:30, first fitter came out at 19:30 found the volts was 256, measured voltage localy and was found to be high, decided to LV backfeed supply and disconnect local transformer, all done by 22:00. They are going to test the local transformer and probably drop the local tap 12%. If they can see a real problem they can act!

 

[IQ Electrical]

Well,
I called the DNO at 18:30, first fitter came out at 19:30 found the volts was 256, measured voltage localy and was found to be high, decided to LV backfeed supply and disconnect local transformer, all done by 22:00. They are going to test the local transformer and probably drop the local tap 12%. If they can see a real problem they can act!

Nice one, good result!

 

[Knobhead]

What’s your next trick, the parting of the waters?

Miracles can be achieved, action out of a DNO!

 

[SW1970]

Good fact sheet IQ. What kit do you use for supply performance monitoring? Cheers SW

 

[UKMeterman]

I suspect the 4 staff liked the 2hr overtime call out...

As for monitoring kit I use a PDA1, I have in the past also used a NEMO 96 energy meter. For most uses I would suggest the Fluke 43 B or similar.

 

[IQ Electrical]

Good fact sheet IQ. What kit do you use for supply performance monitoring? Cheers SW

We use a Chauvin Arnoux 8335, brilliant bit of kit.