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shorty

Hello everyone :)

I've been a memeber for a while now but rarely post but today I was asked a question I couldn't answer so I thought I'd post it here.

Which test certificate should be issued for new (single or three phase) sub electricity meters?

The meters are purely for energy monitoring and don't need to comply with MID as there are no bills being issued.
All meters are CT driven with a common voltage refference (Voltage drop across distribution panel negligable)
None of the existing distribution circuits have been altered, changed or modified.

The discussion is between Minor Works or Electrical Installation testing and certification.

Any further questions just ask but I'd be very interested in peoples experiences/opinions.
 
Hello everyone :)

I've been a memeber for a while now but rarely post but today I was asked a question I couldn't answer so I thought I'd post it here.

Which test certificate should be issued for new (single or three phase) sub electricity meters?

The meters are purely for energy monitoring and don't need to comply with MID as there are no bills being issued.
All meters are CT driven with a common voltage refference (Voltage drop across distribution panel negligable)
None of the existing distribution circuits have been altered, changed or modified.

The discussion is between Minor Works or Electrical Installation testing and certification.

Any further questions just ask but I'd be very interested in peoples experiences/opinions.

Well if you haven't altered any of the characteristics of the installation, a Minor Electrical Installation Works Certificate would be the way to go, if only to document your limited involvment.
 
As above, I assume there is not an actual supply taken to these meters, ie a 230 supply to drive anything or to record anything?

If then as IQ said a MEIWC, though to be honest you could get away with no certification what so ever.
 
As above, I assume there is not an actual supply taken to these meters, ie a 230 supply to drive anything or to record anything?

If then as IQ said a MEIWC, though to be honest you could get away with no certification what so ever.

Agree, ....What's a CT or two amongst friends?? lol!!
 
Thanks for your replies so far.

There would be a TP&N supply taken from a suitable location to provide the voltage reference for the meters to do their power calculations. Sometimes these are new installation, sometimes taken off an existing meters voltage reference.

All electricity meters require voltage and current measurements to perform true power calculations.
 
i could chat about metering all day long but was wondering if anyone had any opinions on the testing of them?

Thanks

P.S. Traditional CTs (Current Transformers) have a 5Amp secondary but there are maybe a dozen different variations.
 
There you are engineer,thats something new you've learned today,so dont bash it
Inspecting & Testing electricity meters {filename} | ElectriciansForums.net
 
Very easily tested shorty, with a secondary injection test kit. Just very expensive to purchase this test kit and also a bit pricey to hire too...
 
Thanks Engineer54 I'm aware of that method for testing the readings/accuracy of the electricity meter and have a suitable alternative.

What is was really getting at was if, according to the regs, the reference voltage would need to be tested with either a Minor Works cert or a new Installation cert. Depending on your interpretation of the regs would depend on if you treat the voltage ref as a circuit or not.
 
To be totally honest shorty, the Regs don't really cover testing of permanent metering and measurement devices. As IQ and Malcolm originally commented, you'd be filling forms in, basically for the sake of recording an activity rather than conforming to any stipulations...

So what alternative method do you use, to accurately test metering CT's ??
 
To be totally honest shorty, the Regs don't really cover testing of permanent metering and measurement devices. As IQ and Malcolm originally commented, you'd be filling forms in, basically for the sake of recording an activity rather than conforming to any stipulations...

So what alternative method do you use, to accurately test metering CT's ??

Firstly you need to define "accuratley" Engineer54. I use two basic methods and if either of them show problems then I'd look at swapping out hardware.

Method 1: Clamp meter used around the same tails/cables/bars as the measurement CT. This provides a good comparison of current measurements.

Method 2: Voltage and current logger connected to the same tails/cables/bars as the measurement CTs. This provides a good comparison of power measurements.

You have to keep in mind that all we're looking for here is the energy consumption from the sub meters. The sub meters (as a system) would be selected to acheive an error percentage of no more than 1% at full scale. We aren't testing the electricity meters themselves, that's what the manufacturers are there for :p
 

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