Electric Metre Multiplyer

Forums › Home Workshop DIY › Electric Metre Multiplyer

1 | 2

gzt

18710 posts

Uber Geek
+1 received by user: 7838

Lifetime subscriber

#733604 17-Dec-2012 14:14

Hilfarion: However, the power bills we've been getting a insanely high, and the multiplyer is the only factory that could be wrong - for example, the metre says we've used 45 units over the weekend (when the building was closed)...

That meter is so old there is no information on the web about it.

How long has your power company been applying this multiplier? Surely you would have noticed before now if your bills were far higher than what you had been expecting due to the multiplier?

If you have a load which you roughly know the wattage of - turn everything else off - then turn on that load for exactly an hour and see what the difference in the meter is. It should be fairly easy to get a good idea of multiplier (or not) from there if the load is constant. A lighting load might be the best for that. Take before and after photos and paste them up here.

There are a few EE people posting on this forum but it may take a day or so before they log in and see this topic. It may pay to hang fire in case they have something to add.

gzt

18710 posts

Uber Geek
+1 received by user: 7838

Lifetime subscriber

#733612 17-Dec-2012 14:24

To state the obvious here regarding the weekend use - if you have a situation where the meter is going higher when nothing or nearly nothing is being used then you have either a serious wiring or installation fault or a meter gone faulty or faulty equipment. For any of that you need a sparky to sort it out.

gregmcc

2173 posts

Uber Geek
+1 received by user: 836

ID Verified

Trusted

Lifetime subscriber

#733613 17-Dec-2012 14:26

Hifarion: This is a shot of the metre, I've tried to work out how they got a mulitplyer of 60x.....

Sorry for the poor quality, it was dark in the metre room...

the x60 is the CT ratio as for every 60KWH going in to the building the meter is reading 1KWH.

cyril7

9075 posts

Uber Geek
+1 received by user: 2499

ID Verified

Trusted

Subscriber

#733626 17-Dec-2012 14:41

Just to clarify, the meter you have is infact a CT meter, note the 1-5A marking on the right this indicates it has a maximum current of 5A, therefore requires a CT to work, its also a 3phase meter note the marking on the left.

Therefore you need to find the CT and see what current ratio is is to confirm if its 60x or not.

Cyril

gregmcc

2173 posts

Uber Geek
+1 received by user: 836

ID Verified

Trusted

Lifetime subscriber

#733632 17-Dec-2012 14:54

cyril7: Just to clarify, the meter you have is infact a CT meter, note the 1-5A marking on the right this indicates it has a maximum current of 5A, therefore requires a CT to work, its also a 3phase meter note the marking on the left.

Therefore you need to find the CT and see what current ratio is is to confirm if its 60x or not.

Cyril

And the only way to find that out for sure is by dissassembling the panel that the CT's are in, something which you WILL NOT be able to do as they are behind a panel that has metering company seals on it.

The CT ratio is a ratio the primary amps to the secondary amps.

300:5 = 60:1
600:5 = 120:1
1200:5 = 240:1
2000:5 = 400:1

It looks like you have a 300A supply, as the most direct metering can do it 100A this is why CT metering is used.

cyril7

9075 posts

Uber Geek
+1 received by user: 2499

ID Verified

Trusted

Subscriber

#733634 17-Dec-2012 14:57

Hi, absolutely, I should have been more clear about how you need to check it, call your retailer and ask them to send an inspector to identify the multiplier. That said, often in larger switchboards the multipliers are behind clear perspex tamper protected covers, so can be seen but not touched or tampered.

Cyril

Apple TV

Stream your favourite shows now on Apple TV (affiliate link).

Bung

6734 posts

Uber Geek
+1 received by user: 2928

Subscriber

#733662 17-Dec-2012 15:27

If 60:1 is the lowest multiplier does this mean that unless there is a fault that the larger Auckland factory is under reading if their bills are lower? Worst case if you have the same supplier is you get stuck with your bill and Auckland gets investigated to see why they are low.

MikeSkyrme

272 posts

Ultimate Geek
+1 received by user: 37

Trusted

#733690 17-Dec-2012 16:12

gregmcc:
cyril7: Just to clarify, the meter you have is infact a CT meter, note the 1-5A marking on the right this indicates it has a maximum current of 5A, therefore requires a CT to work, its also a 3phase meter note the marking on the left.

Therefore you need to find the CT and see what current ratio is is to confirm if its 60x or not.

Cyril

And the only way to find that out for sure is by dissassembling the panel that the CT's are in, something which you WILL NOT be able to do as they are behind a panel that has metering company seals on it.

The CT ratio is a ratio the primary amps to the secondary amps.

300:5 = 60:1
600:5 = 120:1
1200:5 = 240:1
2000:5 = 400:1

It looks like you have a 300A supply, as the most direct metering can do it 100A this is why CT metering is used.

Ok, it is a Monday morning where I am, after a particularly rowdy weekend, but, this does not explain the x60 multiplier. If a 1A secondary was installed where a 5A secondary is required, this is not a factor of 60.
To get 1kWh displayed on the meter, for every real 60kWh consumed, there must be something else in the circuit. Hopefully the OP can post a photo of the complete installation.

Michael Skyrme - Instrumentation & Controls

gregmcc

2173 posts

Uber Geek
+1 received by user: 836

ID Verified

Trusted

Lifetime subscriber

#733763 17-Dec-2012 17:46

ok, here goes the basic explaniation

lets say for arguments sake your place is using 300A, using the 60:1 metering CT's there would be 5 Amps flowing through your meter (the meters maximum capacity), the meter would be recording at fully capacity but only reading 1/60th of the actual power you are using, that's why there is a x 60 mutplier applied.

Can't say i've heard of KWh meters not reading incorrectly, but I'm guessing that the power companies wouldn't want to make it a big deal that they have problems with the metering.

Most likely failure point is the meter it'self, unlikely the CT's have failed,, but that's not to say they havent.

You have 2 choices, ring the power company and ask for a re-certification of your metering, they will most likely ask for you to pay up front, but if it's found to be in accurate then they should credit you this cost. 2nd choice, as I said earlier, rent a power meter and compare the readings from it with what the power companies meter says.

MikeSkyrme

272 posts

Ultimate Geek
+1 received by user: 37

Trusted

#733942 17-Dec-2012 21:42

gregmcc: ok, here goes the basic explaniation

lets say for arguments sake your place is using 300A, using the 60:1 metering CT's there would be 5 Amps flowing through your meter (the meters maximum capacity), the meter would be recording at fully capacity but only reading 1/60th of the actual power you are using, that's why there is a x 60 mutplier applied.

Can't say i've heard of KWh meters not reading incorrectly, but I'm guessing that the power companies wouldn't want to make it a big deal that they have problems with the metering.

Most likely failure point is the meter it'self, unlikely the CT's have failed,, but that's not to say they havent.

You have 2 choices, ring the power company and ask for a re-certification of your metering, they will most likely ask for you to pay up front, but if it's found to be in accurate then they should credit you this cost. 2nd choice, as I said earlier, rent a power meter and compare the readings from it with what the power companies meter says.

60:1 is not the ratio as such. It is the primary rating and the secondary rating. Although the 'ratio' is 60:1, these are the maximum values (in A) that you would see.
If you were to use 300A on a 60:1 CT, it would not work for very long before insulation broke down and the Tx failed. You would also not get 5A out of the secondary windings, as saturation of the CT would have already occured, rendering a non linear output likely.
As the OP says that there is a 'pen' mark (x60) on the meter, I would think it safer to assume that someone (the installer?) has done something else to the circuitry.
I am curious to see what is found, this sort of 'factoring' on a tariff metering circuit does not seem normal..

Michael Skyrme - Instrumentation & Controls

gregmcc

2173 posts

Uber Geek
+1 received by user: 836

ID Verified

Trusted

Lifetime subscriber

#733952 17-Dec-2012 22:00

MikeSkyrme:

60:1 is not the ratio as such. It is the primary rating and the secondary rating. Although the 'ratio' is 60:1, these are the maximum values (in A) that you would see.
If you were to use 300A on a 60:1 CT, it would not work for very long before insulation broke down and the Tx failed. You would also not get 5A out of the secondary windings, as saturation of the CT would have already occured, rendering a non linear output likely.
As the OP says that there is a 'pen' mark (x60) on the meter, I would think it safer to assume that someone (the installer?) has done something else to the circuitry.
I am curious to see what is found, this sort of 'factoring' on a tariff metering circuit does not seem normal..

Um.. what you are saying is not right, I've personally connected up many CT's for CT metering, CT's are a single winding, the secondary winding, the primary is a busbar that passes through the enter of the CT, it's not a 'Voltage transformer' or Tx and they are desgined for voltage conversion. At CT is desgined for current conversion.

If you leave the secondary side of a CT open circuit it will suffer saturation and the voltage rise will cause insulation failure and it will burn out, thats why they are connected to a suitiable KWh or Amp meter to provide load to stop this from happening.

It is impraticle for direct metering for loads above 100A that's why CT metering is used

current transformer

Quic Broadband

Move to New Zealand's best fibre broadband service (affiliate link). Free setup code: R587125ERQ6VE. Note that to use Quic Broadband you must be comfortable with configuring your own router.

richms

29109 posts

Uber Geek
+1 received by user: 10225

Trusted

Lifetime subscriber

#735144 19-Dec-2012 20:11

Any progress on this? I would have thought with a $600 weekend powerbill that it would have motivated some action on it quickly.

Richard rich.ms

1 | 2