600 Amp Meter Base

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Dennis Alwon

Dennis Alwon

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This is the first I have seen these. Self contained but $813.20 from the power company. This is single phase and they make them in 3 phase. I like the compact setup. It is the size of a 320 amp meter base but much deeper for the CT's which you can see in the 3rd photo

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I have a technical question. When I was at the power company who sold me this unit, they were not sure what was line and load. They thought that the units were set so they could come in the bottom and load was at the top. They confirmed that- supposedly. My question is how does the CT know what is line and load. If current is going back and forth does it matter which side is line and load. They said it did so I accept that but why????
 
Dennis Alwon said:
When I was at the power company who sold me this unit, they were not sure what was line and load.
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I've tried zooimg in on the picture but can't tell anything. Have you traced the wiring to see what color goes where and where the polarity marks are?
 
I can see there is a white dot (apparently that was the telling sign for the power company) on the bottom side of the ct's and the wiring for the ct's comes off the bottom side
 
POCO's around here have all of their metering specs documented in detail. Both in a spec book and online.

Yours doesn't?
 
cdslotz said:
POCO's around here have all of their metering specs documented in detail. Both in a spec book and online.

Yours doesn't?
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I was at their main office and they couldn't tell me-- I finally got an answer but it will cost them if they are wrong. Apparently they can set the meter to feed either way.
 
Looks like a form 4S to me. Polarity is usually on the source side of the CTs but you have to make sure both primary and secondary are wired that way. The green wire should go to the secondary CT polarity that corresponds to primary source-side polarity. Same for the red on the other CT. The whites go to the secondary CT non-polarity and is common to both CTs and connects to the neutral.

I can't see the voltage wires but they go to the middle meter terminals with the voltages from the same phase as the CT on their respective sides. So the middle terminal on the left should connect to the phase with the CT having the red current wire. The middle terminal on the right should connect to the phase with the CT having the green current wire.

This gets the voltage and current polarities aligned correctly.

This meter form's accuracy depends on the voltages being reasonably balanced as it only uses the line-line voltage (it violates Blondel's Theorem).
 
This system comes prewired from the factory according to the power company's demands. This is single phase so I am not sure what you mean by the middle terminal. My question was more to do with why the line load would make a difference as the bus is a solid buss with a ct in the middle. How does the CT determine which way the current flows if it cycles back and forth?
 
Dennis Alwon said:
This system comes prewired from the factory according to the power company's demands. This is single phase so I am not sure what you mean by the middle terminal.
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The terminals where the meter plugs in: three vertical on the left and three vertical on the right. The tops and bottoms are the currents and the middle two are for the voltage input.

Dennis Alwon said:
My question was more to do with why the line load would make a difference as the bus is a solid buss with a ct in the middle. How does the CT determine which way the current flows if it cycles back and forth?
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The current is measured in real time relative to the voltage. Flux from the current coil works with the flux from the voltage coil to measure the energy.

For a resistive load we want the current wave to reach a positive peak when the voltage wave reaches a positive peak. Reverse either one and the meter still records volts times amps but it thinks it is energy being generated by the customer and delivered to the POCO (or for some meters it records zero if no reverse metering is allowed).
 
Some meters pay no attention to the sign of the VxA components

Some meters pay no attention to the sign of the VxA components

Some meters don't care, I have a group of electronic KWH meters originally Ontario Hydro that run forwards when plugged in right side up, and up side down. My guess is that they read the current and the voltage and multiply them ignoring the sign, using just the magnitude.

I discovered this when I used one as a meter socket shunt (we were temp feeding a building on which we had installed a meter socket) from another load side of a real revenue meter and I stuck it in upside down so no bozo meter reader would actually read it, or if they did would probably raise a stink that it was flipped so I could disabuse them of their assumption.

I'll admit I was not expecting it to run forwards.:?
 
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fmtjfw said:
Some meters don't care, I have a group of electronic KWH meters originally Ontario Hydro that run forwards when plugged in right side up, and up side down. My guess is that they read the current and the voltage and multiply them ignoring the sign, using just the magnitude.

I discovered this when I used one as a meter socket shunt (we were temp feeding a building on which we had installed a meter socket) from another load side of a real revenue meter and I stuck it in upside down so no bozo meter reader would actually read it, or if they did would probably raise a stink that it was flipped so I could disabuse them of their assumption.

I'll admit I was not expecting it to run forwards.:?
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So does this meter also register apparent power on the display instead of just true power?

If so then the people selling the boxes with capacitors would have more validity to their claims if the POCO used such a meter.
 
Dennis Alwon said:
This system comes prewired from the factory according to the power company's demands. This is single phase so I am not sure what you mean by the middle terminal. My question was more to do with why the line load would make a difference as the bus is a solid buss with a ct in the middle. How does the CT determine which way the current flows if it cycles back and forth?
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Smaller self contained meters work in similar fashion, if you plug them in upside down or back feed them the display will count down instead of up.

POCO meter nerds that build their own CT metering have to get the right polarity on the CT's or they will also have descending values in the recording.
 
kwired said:
So does this meter also register apparent power on the display instead of just true power?

If so then the people selling the boxes with capacitors would have more validity to their claims if the POCO used such a meter.
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I suspect the multiplication is of the vectors for voltage and current values. Not counting down when the meter is plugged in backwards might be a feature as far as the power company is concerned.

A simple power theft hack is to flip your mechanical meter for part of the time (when the meter reader is not scheduled) and let it subtract for a while.

Also I don't know that revenue meters in general are required to handle reverse flow in any particular way.

In the era of mechanical meters a ratchet was sometimes used to prevent reverse operation.

Also meters used for telemetry (with a contact closure pulse per disk rotation) would not distinguish rotation direction.
 
fmtjfw said:
I suspect the multiplication is of the vectors for voltage and current values. Not counting down when the meter is plugged in backwards might be a feature as far as the power company is concerned.

A simple power theft hack is to flip your mechanical meter for part of the time (when the meter reader is not scheduled) and let it subtract for a while.

Also I don't know that revenue meters in general are required to handle reverse flow in any particular way.

In the era of mechanical meters a ratchet was sometimes used to prevent reverse operation.

Also meters used for telemetry (with a contact closure pulse per disk rotation) would not distinguish rotation direction.
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They use seals and locks to prevent people from tampering - doesn't mean people still don't find some ways around those obstacles at times though.
 
Dennis Alwon said:
Here are some more pics

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Left Side CT

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Right Side CT

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See how there is leads to each CT? Those are what sends current signal to the meter. There is also a control lead to each bus. These not only provide power to the metering equipment, but are also polarity sensitive to the metering, as they must correspond to the correct CT for proper recording of power. Connect a voltage lead to the wrong place in relation to current leads and you don't get accurate recording. Reverse polarity of individual current leads and you get inaccurate recording. Get the right combination but in reverse, the recording is accurate but is negative instead of positive accumulation on the display.
 
So if I connect to the top and they connect to the bottom then they can just switch leads if it is wired incorrectly? I thought they were saying that the CT's would have to be removed and turned around.
 
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