A strange current problem 2

[hhhansen]

Hi there
I am experiencing a quite strange problem which I am no yet able to explain. A single phase power line, 132 kV (solidly grounded) is feeding electrical trains rated 25 kV through a transformer 132/27,5 kV. The connection at 132 kV is between phase R and T. Current on T is measured from a 300/5 core class 0, 2 S. Current on phase R is measured with a seperate identical core. Voltage is messured by a capacitive voltage devider 132 kV/110V. Each secondary current is fed to a billing meter (main and control meter class 0,2). The line voltage is common for each meter.
When measuring the yearly energy consumption we can notice a deviation around 2-3% corresponding to 500.000 kWh/year. This difference we can not explain by the overall measurement error in the system.
But what might be the problem?
I have thought about capacitive leakage current and current harmonics.

Best regards
Hans-Henrik

 

[Skogsgurra]

Most modern trains have some sort of variable frequency drive these days. And they do distort catenaria current.

A few years ago, I helped a utility company with energy meters that did show a lot more than they were expected to show. The brand is rather common - there were 285 000 of them in Sweden at the time - and they mostly behaved well. But certain waveforms made them register a lot more energy than is actually consumed. Especially waveforms that are produced by dimmers and other thyristor controllers. The "de-identified" report is available here:

http://www.gke.org/arcus/files/Electricity meter report March 2010 1.pdf

The utility has changed meters where customers have complained and everything seems to be OK now. The cutomer's energy consumptions are back to normal and there seems to have been some silent agreement, including compensation. The report has been sent to the manufacturer and also to the authorities. Total silence from their part, so far.



Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

You did some impressive work on that earlier problem Gunnar. I as and am impressed.

Bill
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"Why not the best?"
Jimmy Carter

 

[hhhansen]

Hi Skogsgurra
Thank you very much for the report. I would like to ask if the report touches the problems with different values of registered currents in a main and control meters. We did actally change both meters to another brand (they are now Schlumberger SL7000 billing meters) and that has not solved the problem.

 

[Skogsgurra]

No, it does not discuss the registered values or import and export registers. We measured the blinks on the front panel, the hardware output was coded and could not be used easily. The blinks were the only "information source" that was equally reliable between the different meter brands.

And I can say that the meters that caused problems were not Schlumberger. But, with todays branding and labelling, who knows who does what?


Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.