High voltage meters

[JohnW2]

he poiint to look at with the HV taarrif is that most are not just about units used!

I'm sure that's all true and that 'the bill' is probably based on a lot more than just 'units used' - but the OP was reporting something like a 40:1 disparity between HV and LV meter readings of units used, which is obviously not affected by tariff.

Kind Regards, John

 

[westie101]

I'm sure that the OP, at the bottom of it all is worried about the threat of disconnection and the cost of reconnection,. As well as explaining the costs of electricity at what is a closed down site

Whilst a discussion about the whys and wherefores of the discrepancy between the HV and LV is of great interest (Fixed and load losses on the TX & metering VT) I'm sure the cost is of great importance.

In a lot of cases liike this it is often found that itt is down to the metering issues.

We do not know what is being compared, is the OP just reading units used as the source of the HV cost? If so there will be a huge descrepency as unit costs usually only form a part of HV metering charges

 

[JohnW2]

I'm sure that the OP, at the bottom of it all is worried about the threat of disconnection and the cost of reconnection,. As well as explaining the costs of electricity at what is a closed down site ... I'm sure the cost is of great importance. ... We do not know what is being compared, is the OP just reading units used as the source of the HV cost? If so ....

Whilst I'm sure that the money is of great importance, as far as the electrical issue is concerned, we can really forget everything we've been told about costs. The electrical issue described in the OP is that LV metering is showing an average usage of 12 kWh/day and the HV metering is showing 500 kWh/day - and that relies on no assumptions about how those figures translate into costs. Even if the 'empty'' building is using only a small fraction of the available supply, that degree of disparity is surely (electrically) ridiculous, isn't it (again, regardless of how all that translates into cost, which is a contractual, not electrical, issue)?

Kind Regards, John

 

[westie101]

Yep!

At the end of the day the HV meters will be measuring the No load losses of the transformer
The LV meters will NOT be measuring his value!

The owner needs to find out based on the spec of the transformer he owns what the expected losses will be.
He then needs to take account of that inn his calculations

 

[JohnW2]

Yep!

I'm not sure what that is a response to - are you agreeing that the degree of disparity is 'ridiculous'? The respective HV and LV meter readings are an electrical issue, and will in no way be affected by tariff/contracts.

At the end of the day the HV meters will be measuring the No load losses of the transformer ... The LV meters will NOT be measuring his value!

Yes, I realise that. Maybe I'm naive (it's certainly not a world I know anything about) but I had rather assumed that, unless we were talking about the supply to the Boeing factory, those transformer losses would not be expected to be anywhere near 500 kWh/day. Am I wrong?

As others have said, I think we would be able to put all this into much better perspective if we knew the size of the supply (or previous, 'when working' load).

Kind Regards, John

 

[Lectrician]

HV is usually far cheaper per unit, but as with any HV or LV "large" supply, there will be an availability charge based on the agreed capacity and other fees payable, but the OP is talking purely about units consumed.

The transformers are not usually not too inefficient these days, but do still consume units - I would hope not 500kwh/day unless there is something wrong with the TX or supply cables.

HV metering is pretty crap at low loads though, it is more accurate close to the agreed capacity of the supply.

 

[westie101]

A little bit of a dig finds that the no load "iron" loss for a 1000kVA transformer is between 1100W and 1700W

OOK there is still sme way to go, but this is a start

 

[JohnW2]

HV is usually far cheaper per unit, but as with any HV or LV "large" supply, there will be an availability charge based on the agreed capacity and other fees payable, but the OP is talking purely about units consumed.

Exactly, in relation to the apparent underlying (electrical/metering) issue that the OP asked about (and gave us figures for) the mechanics (and level) of the charging are irrelevant.

The transformers are not usually not too inefficient these days, but do still consume units - I would hope not 500kwh/day unless there is something wrong with the TX or supply cables.

As I said, although it's a field I know virtually nothing about, that would be my expectation.

Kind Regards, John

 

[JohnW2]

A little bit of a dig finds that the no load "iron" loss for a 1000kVA transformer is between 1100W and 1700W ... OOK there is still sme way to go, but this is a start

I would say a very small start If my sums are right, I think we're 'looking for' something like 21,000W. Of course, we still don't know what size this tranny is.

Kind Regards, John

 

[ericmark]

All I can say is when working on the Falklands we had three 250 kVA LV generators in a shed which supplied the workshops and office complex.

At the time when most the office complex was gone and the workshop was only doing a fraction of the work it had done the electrical engineer called me to try and explain the amount of power used.

Armed only with a two way radio and two clamp on meters we tested each supply and found one had a greater output to input to the board it supplied.

My thought was early in the contract we had run out of cable jointing kits and we had been forced to use denso tape make careful notes of where used and when the boat with cable jointing kits arrived dig them back up and do it properly. But this was some three years earlier.

We were looking at around 10 kVA or more so the electrical engineer felt it was unlikely this could be the cause. However that night it snowed and there was a large area where the snow had melted.

So we got a digger and looked for the cable. And yes it was an old denso tapped joint where who ever had done it failed to record the repair so it had never been re-done with a proper cable jointing kit.

Now I seem to remember years ago being shown where with the older meters taking power from line to earth rather than line to neutral did not register as much power on the meter. This was some 30 years ago so I suspect that no longer works but from the sound of it the premises are rather old so may be the power is going to earth with a faulty cable.

This would also explain the variable results.

Please do say what you find it will be interesting.

 

[JohnW2]

At the end of the day the HV meters will be measuring the No load losses of the transformer ... The LV meters will NOT be measuring his value!

It has just occurred to me that the OP has told us that when all LV loads are removed, the HV metering (as well as LV metering) shows zero energy usage. That surely indicates that the "no load losses of the transformer" must be less than the minimum that the HV metering can detect/display ('10 units' has been suggested), doesn't it?

Kind Regards, John

 

[JohnW2]

... We were looking at around 10 kVA or more so the electrical engineer felt it was unlikely this could be the cause. However that night it snowed and there was a large area where the snow had melted. ... So we got a digger and looked for the cable. And yes it was an old denso tapped joint where who ever had done it failed to record the repair so it had never been re-done with a proper cable jointing kit.

In the OP's case, the HV metering shows zero usage when all LV loads are disconnected, so I don't think that the discrepancy between HV and LV meter readings (when there are small LV loads) could be explained by loss of energy into a cable fault, could it?

Kind Regards, John