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# energy meter

## energy meter

(OP)
hi every one can u tell me about energy meter that what would happen if we use one phase

### RE: energy meter

No, without any useful info about the meter we really can't.

In theory, it should measure the energy on each phase and then give a sum of the energy used. But I can't say if that will be true in practice without meter details.

### RE: energy meter

Most meters I've destroyed only measure one incoming phase... ripe for energy theft if you know what you're doing.

Dan - Owner
http://www.Hi-TecDesigns.com

### RE: energy meter

It depends!!!

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: energy meter

There are wiring diagrams available from most meter manufacturers web sites that detail how to connect a multi phase meter single phase.

### RE: energy meter

Well given that I have seen single phase meters used in a way that gave inaccurate results, I have to state that without some more information as to what exactly you intend to meter and with what, your question can not be answered as stated.
The basic rule of metering is that you need N-1 elements to meter accurately. N being the number of current carrying conductors.
I have seen this rule violated by persons who were not aware of the rule.
There are accepted three phase schemes which are capable of working with N-2 elements. However these schemes depend on an assumption that the phase voltages and phase angles are equal. I have inherited systems where N-2 metering was used on a system where the voltages and angles were not equal. The result was inaccurate metering. The solution was to replace the meters with meters meeting the N-1 rule.

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: energy meter

So you have a properly wired 3 element meter connected to a 3 phase 4 wire source, and connect a single phase load either phase to phase or phase to neutral; yes it will meter it properly. Or you have a properly wired 2 element meter connected to a 3 phase 3 wire source and connect a single phase load phase to phase; yes it will meter it properly. Is this the question?

### RE: energy meter

#### Quote:

Most meters I've destroyed only measure one incoming phase

If we're talking about utility revenue meters, this is not correct.

### RE: energy meter

Hi,
I think that you are asking 'can a normal 3-phase digital power meter be used for a 1-phase application'.
If that is what you are asking, then the answer is yes.
I did exactly that last year,on a small 75kVA 240/120V 1-phase service, with a PML-7350 meter. I sure that other meters can be configured to work on 1-phase services as well.
Good luck.

### RE: energy meter

I had an application to meter a four wire three phase service with a two element meter.
This connection is included in the Westinghouse "Meter and Instrument Transformer Application Guide".
The connection uses delta connected CTs.
I had not used this connection before and lacked confidence.
Most revenue metering connection errors will result in a fairly large error, 2:1, 1/3, 2/3, 1/1.73, 2/1.73.
The load was mostly three phase motors but included fairly well balanced single phase loads also.
I temporarily installed a single phase meter in an out of the way location.
I checked the meter readings every couple of weeks for a few months. The single phase meter was tracking at 1/3 of the three phase meter within a couple of percent.
This gave me the confidence that I had been lacking.
Footnote;
This connection assumes that the phase voltages and phase angles are equal.
At a later date we lost one phase of our submarine cable to the Island. A replacement single conductor cable was laid parallel and a couple of feet away from the original twisted trefoil cable.
The dissimilar impedances upset our voltage and phase angle balances such that we were no longer able to meter accurately with two element meters. We replaced our two element meters with three element meters and restored metering accuracy.
On the other hand I have seen single phase meters used in an attempt to meter services derived from two phases of a three phase supply.
The meter accurately measures the consumption of any 208 Volt loads but under meters the consumption of 120 volt loads at a factor of 208/2:120 or 0.866

Bill
--------------------
"Why not the best?"
Jimmy Carter

### RE: energy meter

#### Quote (dpc)

If we're talking about utility revenue meters, this is not correct.
Let me rephrase, removing the need for further clarification, smilies, etc.... the current sensor was applied to a single leg of the incoming 240V.

Dan - Owner
http://www.Hi-TecDesigns.com

### RE: energy meter

Two ways to meter 120:240 Volts with a three phase meter.
1> Use two phases of the meter.
2> Use one phase of the meter, one CT and route L1 and L2 through the CT in opposite directions.
Applying the current sensor to one leg of the 240 Volts will not accurately meter 120:240 Volt circuits.

Bill
--------------------
"Why not the best?"
Jimmy Carter

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