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Author Topic: Large 3 phase CT meter. Is it right?  (Read 4655 times)
guydewdney
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« on: June 09, 2018, 08:38:14 PM »

We have a large property with 3 phase. It is so big that the meter isn't direct, it uses CT clamps like the OWL meters etc.

When I had one of those type wireless energy monitors, it used to read all sorts of twaddle with low energy stuff.

So.... Is my meter reading massively high for the same reason? My last bill was 4500 quid a quarter.......... The electric company asked me how big my pool facepalm was....


« Last Edit: June 10, 2018, 08:52:26 PM by guydewdney » Logged

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rogeriko
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« Reply #1 on: June 09, 2018, 10:21:57 PM »

Just buy another 3 phase meter with 3 current transformers and connect it yourself and see if the readings are the same over a one month period.. Shouldnt cost more than 200 pounds all in. Maybe half that if you search around.

Example

https://www.decmetrics.co.uk/product/elster-a1140-three-phase-meter-current-transformer-version/
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knighty
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« Reply #2 on: June 09, 2018, 11:40:28 PM »

how big are your main fuses?

at work I'm on 100amps/phase

but it's a normal old fashioned meter with feed in and out of it and spinning disks

bill averages £2000/month  (mostly big freezers)
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guydewdney
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« Reply #3 on: June 10, 2018, 08:58:49 AM »



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guydewdney
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« Reply #4 on: June 10, 2018, 09:01:12 AM »

I canít see the fuse rating. Thereís two standard 16mm type cables per phase coming out of the incomer if that gives some indication.

How would a second meter help? The issue might be that CTs assume voltage and power factor is about 1, whereas with a lot of led lighting (about 300 bulbs, 3 to 5w each) the pf is not 1.
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Iain
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« Reply #5 on: June 10, 2018, 09:06:37 AM »

Hi
I would imagine they are monitoring the voltage at each phase as well so it should have the correct power factor by comparing the phase angle.
I think a second meter was suggested just to check if both read the same.
Could a CT be the wrong way around? Not sure how you can check and even if it would make a difference. It would  alter the Power factor reading I think.
Iain

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A.L.
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« Reply #6 on: June 10, 2018, 09:44:16 AM »

hello,

The issue might be that CTs assume voltage and power factor is about 1, whereas with a lot of led lighting (about 300 bulbs, 3 to 5w each) the pf is not 1.

- CTs can measure power factor if correctly constructed, not saying yours is though.................

https://www.navitron.org.uk/forum/index.php/topic,12168.msg133671.html#msg133671
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azps
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« Reply #7 on: June 10, 2018, 10:49:37 AM »

So.... Is my meter reading massively high for the same reason? My last bill was 4500 quid a quarter.......... The electric cc implant asked me how big my poo facepalm l was ....

Yeah, them saniflo's really can burn power, eh?
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rogeriko
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« Reply #8 on: June 10, 2018, 10:53:45 AM »

The meter is a relatively new digital type but the CT's look about 40 years old. I wonder when they changed the meter did they check the CT's were the right type?


Modern CT



* SR400.jpg (53.75 KB, 500x500 - viewed 226 times.)
« Last Edit: June 10, 2018, 10:59:27 AM by rogeriko » Logged

guydewdney
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« Reply #9 on: June 11, 2018, 02:50:40 PM »

CTS are 200/5 and meter is set to 200

PF is 0.78  Shocked leading
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Scruff
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« Reply #10 on: June 11, 2018, 02:58:31 PM »

I've seen pf of 0.4 on LEDs through a load compensating charger.
I heart DC.  lovefirefox

0.8 is normal for uncorrected installations.
« Last Edit: June 11, 2018, 03:00:32 PM by Scruff » Logged
jonesy
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« Reply #11 on: June 11, 2018, 11:05:17 PM »

If you are a business, they may well be billing you in VA, so a poor pf will cost you more, vs domestic. I think a pf of 0.5 will cost you double a domestic client. What is a normal size bill?
Led lamps can have a pf of 1, but most are worse. I've a bunch of freebies with a pf of 0.5, given to me by the power companies, so they then have to manage the VAr on the network which I understand is tricky.
Turning on a large immersion should move the pf towards 1, so that will give a crude idea things are installed the right way. Commercial meters will read just fine with all sorts of crappy waveforms.
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roys
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« Reply #12 on: June 12, 2018, 08:10:28 AM »

How come your PF is leading, are you running large runs of fluorescent lighting?
Most installs tend to run with a lag PF.
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Iain
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« Reply #13 on: June 12, 2018, 08:40:15 AM »

How come your PF is leading, are you running large runs of fluorescent lighting?
Most installs tend to run with a lag PF.


Unless the CT's are or a CT is connected the wrong way around?

Iain
« Last Edit: June 12, 2018, 09:13:50 AM by Iain » Logged

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Westie
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« Reply #14 on: June 12, 2018, 08:45:23 AM »

How come your PF is leading, are you running large runs of fluorescent lighting?
Most installs tend to run with a lag PF.


Unless the CT's are  or a CT is connected the wrong way around?

Iain

I agree, definitely something wrong, it's virtually impossible to get a leading Pf of that magnitude, check you CT polarities.
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