Medium to high voltage measurements

[Gauss2k]

We would like to take measurements on a 25kV transmission line (voltage and current). Other than installing permanent current and voltage transformers, is there something else we can use to record those values over a short period of time?

A few months ago, I remember receiving a publicity from The electricity forum about a current probe that can be clamped on a power cable. It records the current over a period of time and the datas can later be downloaded to a PC. The problem is I can't find what was the name of that product...

Anything else that could be suggested to make such measurements on 25kV or higher? Something using fiber-optics, radio transmission, memory recording, or anything else?

 

[apowerengr]

Hastings makes their Max-I-meters for drag-hand amps. Metrosonics makes (or at least used to make)the PF-1 and PF-1R recorders which measure and record amps (PF-1) and amps/displacement power factor (PF-1R); with their software you can input an assumed voltage and it will calculate kW, kVA, kVAr, etc.
Does your voltage vary so much that you need actual potential measurements? Rochester Instruments (RIS) used to make their Loadlogger which recorded amps only, not displacement power factor.

 

[ScottyUK]

It seems slightly surprising that there are no permanent CTs and at least one VT anywhere on the line - is there no possibility of tapping in to these? If you use a split-core hall effect sensor you can effectively tap in to a CT secondary without breaking the circuit e.g. if that CT already serves a protection relay and you do not want to compromise the integrity of the scheme this would be a good solution.



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Sometimes I only open my mouth to swap feet...

 

[raadhatab]

I agree with scottyUK, however there must be C.Ts& V.Ts installed in the step up and step down switch yard (if AIS), otherwise how were these substation commissioned energized, further information's will be very useful

 

[Gauss2k]

Of course, we use the cts and vts when available, which is most of the time. I must say I don't really enjoy the idea of taking measurements on live medium voltage cables. Even if every and all precautions are taken, there is still a higher risk than working on cts and vts.

But we have received a few requests for such measurements on medium voltage networks. One of them is from a client that that is receiving his power from the utility to his main transformers and then feeds other buildings through his private medium voltage network. Several of those transmission line have no measurement installed and they would like to monitor some of them.

Another only has metering on the low voltage side of his main transformer, but he would like to monitor the medium voltage side for power quality issues (voltage variations, imbalance).

Thanks for the references. Hastings does have a few HV products, but the best I've seen so far seems to be

http://www.hdelectriccompany.com

They make HV ammeters, voltmeters, recorders, etc. I'll take a look at their technical documents

 

[jghrist]

You are probably thinking of the power donut. See

http://www.usi-power.com/Products & Services/Donut/PowerDonut2 Cell.pdf.

"The Power Donut2 is completely self contained: it is self powered, it measures current, voltage, MW, MVars, MWh, conductor temperatures, stores data on board, and it transmits data on demand using GSM wireless cell phone technology."