Sub-station Capacity Problems - Power Quality Effects to Customers?

[kingtech]

Hello,

I am working with a customer on evaluation of a power regulation device on their facility. I am a thrid party that has been hired to assess feasibility. This is device is being marketed for power regulation. I am trying to assess the possibility that the voltage in the customer area is being supplied on the high side of allowable limits. The customer's substation is within a large, modern city. In this particular area, the sub-station is definitely at capacity limits according to the network operator.

What would be the possible affect on supply voltage? Would it be higher than normal during peak times? I appreciate that my question may be obtuse, but I am just trying to assess the possibility that there are power quality issues at the facility. I am not an electrical power engineer, so please forgive me if this seems like a silly question.

Any response will be much appreciated!

Thanks

 

[jghrist]

I would expect that operating the substation at its capacity limit would more likely result in low voltage that in high voltage. If the substation, or the feeder that customer is on is regulated, there may not be any effect on the voltage. If you want to assess the possibility that the supply voltage is high, the best way would be to measure it over a period of time.

 

[Marmite]

Most if not all Network Operators have statutory limits that they have to maintain for their customers with regards to voltage and power quality. The first thing you have to do is establish whether the customer has a problem by taking on site measurements, otherwise there is a risk of purchasing a solution for which there is no known problem.
Regards
Marmite

 

[crshears]

LPS for you, Marmite; a shady outfit may try to fabricate a problem just to make a sale, not caring about the wreckage they leave in their wake because there'll be another sucker along in a minute.

Speaking to jghrist's comment: topology can have profound effects on how voltage regulates at any given customer's connection point...

By way of example, a transformer station that supplies only relatively short, densely loaded urban feeders need not bother with implementing load drop compensation at the TS since the relatively small voltage drop along the feeder even at heavy loads does not cause off-spec voltage problems for any of the customers.

If on the other hand s station on the edge of a metrobolitain centre supplies both load within the city and rural feeders extending for some distance from the TS, the voltage profile can become problematic.

Also, depending on how litigious the customers that a utility supplies are, the utility may be understandably quite reticent/reluctant when it comes to sharing voltage profile information about any given location...

It would be very much to your benefit to arrange for the longer-term collection of voltage profile data for your customer's site; but be sure to insist on using a meter or recording device that will capture short-duration steep-front spikes and/or dips, and not just average voltage values.

Anecdote:

I haven't had to be directly involved in this aspect of PQ for some time, but I do recall once being in a friend's basement rec room and hearing this weird repetitive ticking sound coming from somewhere. When I asked what that noise was, I was shown the "meter" the utility had connected to the residence's incoming feed: it was what we at that time called a "woodpecker" that snapped an incoming voltage trace onto no-carbon required trace paper every ten seconds or so. The utility had connected this device in response to voltage complaints my friend had made.

Out of curiosity I asked what sorts of problems had been observed in the house, and was told about drop-out 'blinks' and quick flashes of the lights, like lightning superimposed on an otherwise smooth voltage level. I advised my friend that the woodpecker would only record the average voltage, and was very unlikey to capture either of the problems he described unless the snap of the recorder occurred at the very instant of the spike or dip, and that he should insist the utility place a continuous-trace fast-acting ink-trace recorder instead. If he didn't, the utlity would use the existing trace as "evidence" there wasn't a problem at all and refuse to address the issue.

End of story; hope this helps.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[111R]

If by "at capacity limits", they mean that the distribution feeder circuits are undersized for the current load, they may be bumping up the regulators or LTC to prevent low voltage near the end of the line and it's causing excessively high voltage near the feeder exit.

Without more information on this regulation device, it's hard to guess.

 

[ScottyUK]

Hey Marmite,

I read your last line as "... a risk of purchasing a problem for which there is no known solution. " We bought one last year.