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Power frequency

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ssembo

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Hello guys, how can the frequency of a power bus bar on a substation measured? What instrument is used?

Thanks.
 
How much voltage is on the bus bar?
 
If it's a power bus then a simple couple wraps of wire around the bus bar would be used as a current transformer and fed into a measuring circuit, the current going through the bus would determine the number of turns you'd need. It's the exact same method a clamp style amp meter uses, the scales just a bit larger.
 
ssembo yes, you'll be getting a fluctuating current that mirrors the current going through the bus bar exactly, including it's frequency, you simple measure the voltage generated on the sense coil with a frequency meter.
 
About the clamp, i will be getting current...i was wondering what i can use to determine the frequency.
Depends upon the desired resolution and frequency.

A digital oscilloscope will give a good basic measurement.

For best accuracy use an accurate digital frequency counter. You can count over many seconds to improve the resolution. Also measuring the waveform period and calculating the frequency from that can give better resolution for a short measurement period than measuring frequency directly.
 
Hello guys, how can the frequency of a power bus bar on a substation measured? What instrument is used?

Thanks.

33kV busbar.

If you want to measure the line frequency of a 33 KV bus bar in a power sub station all you need to do is find a DMM that measures frequency (Fluke 87 or like) and connect about a 6 inch lead to the input high side and stand anywhere close. Personally I would not stand real close either. :)

Ron
 
Reloadron, if you're monitoring the frequencies of a substation like that, single hertz accuracy is gonna be useless, you'll want two decimal places or better past zero.
 
Reloadron, if you're monitoring the frequencies of a substation like that, single hertz accuracy is gonna be useless, you'll want two decimal places or better past zero.

Maximum Frequency 200 kHz
Accuracy ±(0.005%+1)
Maximum Resolution 0.01 Hz

Fluke 87 which is why I said Fluke 87 or like. I can place a single mini grabber lead in the high side and place it beside an outlet and read line frequency. Simply by proximity.

Running down my street we have 3 phase 13.3 KV and below that 3 phase 7 KV. Despite it being 3 phase I can walk across the street meter reading nothing. Soon as get under the poles I read 60.01 Hz. I guess it is a matter of country and how accurate you want to read the line frequency. The 13.3 KV is about 50 feet above the ground and the 7 KV is about 10" below it. I would imagine if you want better accuracy you could find a small hand held auto ranging frequency counter and improve the accuracy. Long as the counter has good sensitivity. I just don't see any need to attempt to wrap a few turns of wire around a 33 KV bus.

<EDIT>
Additionally for the benefit of ssembo. I have no clue why you would want to sample mains frequency in a sub but then too my knowledge of the Uganda power grid is not that great as in I am clueless. However, even here in the US while mains frequency is pretty accurate it is sampled and charted over long periods of time with corrections being added periodically. For that reason, here in the US (and I believe Europe) a single mains frequency measurement is rather useless, rather constant sampling is in place with scheduled corrections.
</EDIT>

Ron
 
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What's the accuracy value in relation to? Is that .005% plus or minus the first digit? That's damn good, but the OP needs to state is reasons for needing to monitor the frequency and his needs to figure if that's good enough.
 
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Why are you reading all this superfluous stuff into their question?

Might help to re-read it. They asked:

Hello guys, how can the frequency of a power bus bar on a substation measured? What instrument is used?

Nothing about accuracy. Nothing about anything except how and what device. Why not just try to answer that?
 
What's the accuracy value in relation to? Is that .005% plus or minus the first digit? That's damn good, but the OP needs to state is reasons for needing to monitor the frequency and his needs to figure if that's good enough.

I have no clue where the OP is going with all of this? Beats the heck out of me. Again, I also have no clue how well Uganda regulates mains frequency? Another beats the hell out of me. :)

Absolutely nothing derogatory intended towards ssembo but I figure it this way. If someone needs to ask how to measure mains frequency in a 33 KV sub station I just don't think they should be attempting anything in the sub station.

We are currently replacing our small sub in my building (part of a large complex). We currently have a 5 KV sub with two transformers that give me 480 Volts with a max of 3200 Amps (1600 X 2). I hate that room! :) Just for entry you suit up if you will be opening any panel. They are real funny about that stuff.

The concrete pads were poured last week (damn rain) finally for the new outside sub. All the underground ground plane work is done and inspected. We considered both 13.3 and 25 KV and settled on 13.3 KV. Even though the rate is slightly higher for 13.3 the cost of 25 KV switch gears is astonishing. It would take over 25 years to offset the cheaper power.

Back to the little Fluke? That +/- 1 count is the LSD so is it great? Hell no but not bad for something that can be dragged around. The few times I dragged it to work and compared to the time and frequency standards it was dead accurate as far as what it could resolve. We have a few applications where we do care about mHz but not many and for those we use real counters.

Ron
 
Why are you reading all this superfluous stuff into their question?

Might help to re-read it. They asked:



Nothing about accuracy. Nothing about anything except how and what device. Why not just try to answer that?

Uh, because it's a boring Sunday afternoon? :)

Ron
 
carbonzit, there is no question without a specific application and tolerance ranges. There was no question that could be fully answered simply from the original post, or it would have been which is why all the questions occur and discussion commences which allows us to determine the posters needs so that we can properly provide them with an answer.

You can play soccer with a ball, you can play lacrosse, you can play baseball, American football, tennis, golf or any number of other types of games with a simple ball. But the game is defined by the rules and how you use the ball.
 
Thanks for all the infomation. I wanted to monitor the frequency of a busbar and use it to make decissions of when to start and synchronise on generators. Ron, u remember! Was here sometime back and Ron taught me some stuff. I enjoyed.

Atleast am learning something from these discussions.

thanks
 
I wanted to monitor the frequency of a busbar and use it to make decissions of when to start and synchronise on generators.
So, you want to know when to connect an extra generator onto live busbars?
Once the generator frequency is somewhere near, you use a synchroscope (google it) to ensure that the generator and the busbars are in phase in order to decide when to close the circuit breaker.

JimB
 
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