Open Wye Primary / Open Delta Seconday Banking Connection

[Raffy2019]

Hi everyone!

I would like to seek for your comments if the banking connection in my subject would be the reason why the electric bill of my client increased after I had completely installed solar in their system consisting 1- 2.5kVA and 1-5.0kVA inverters. the increase was observed 1 month after the meter was reconfigured for net metering.

 

[waross]

It sounds as if the meter is still in the default configuration. This is not the first time a consumer has been billed for power returned to the grid.

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

 

[jghrist]

I don't see why the transformer connection would affect the billing. Was it changed at the same time that the inverters were installed? Do the inverters serve the 3Ø load?

 

[waross]

I had an issue one time with a change in transformers.
The new connection resulted in the metering multiplier being halved and the original multiplier continued to be applied.
No-one realized at the time. After complaining bitterly for about a year, I was called and got a plane ticket to Central America to sort things out.
The double billing by that time was close to $100,000
Based on my report to the board of directors, the utility made a full adjustment and gave full credit to the customer.
Moral: It may be a multiplier issue.

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

 

[Raffy2019]

Hi waross,

I mean maybe the voltage and current phase angle displacement would affect the reactive power calculation of the meter the way it was configured for net metering. I guess the open wye / open delta have different phase angle displacement of current and voltage since it only utilizes two phases of MV lines. Moreover, I only have two inverters which means I only supplementing power for two phases of the system. Do you think this causes the high billing?

 

[waross]

The default setting of many electronic HWHr meters is to sum the forward power with the reverse power.
If the only change was that the inverters were connected and the bill went up, the meter is probably on the default configuration.
or,
The load increased at about the time that the inverters were connected.
or
The metering connections were changed.
or
The multiplier has been changed.
It may have been wrong and been corrected.
The metering connections were changed and the multiplier should have been changed but wasn't.

I guess the open wye / open delta have different phase angle displacement of current and voltage since it only utilizes two phases of MV lines. Moreover, I only have two inverters which means I only supplementing power for two phases of the system. Do you think this causes the high billing?

No. It doesn't matter. With proper metering you pay for the net power that you use.

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

 

[jghrist]

I mean maybe the voltage and current phase angle displacement would affect the reactive power calculation of the meter the way it was configured for net metering. I guess the open wye / open delta have different phase angle displacement of current and voltage since it only utilizes two phases of MV lines. Moreover, I only have two inverters which means I only supplementing power for two phases of the system. Do you think this causes the high billing?

The current/voltage phase angle displacement is determined by the load power factor, not the transformer connection.

 

[waross]

Has there been any additional load added at about the same time that the inverters went into operation?

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

 

[ElectricRob]

If the meter was replaced, and the old meter was electromechanical, it's possible that the old meter was registering slow and the new meter is just correct. I'd be interested in the knowing their typical consumption before and after the installation. Before my utility switched to solid state meters, every electromechanical meter we brought in for testing registered slow. Most were 1-2% slow, but we occasionally found them registering 50% or so.

Most open-wye, open-delta services that I've done have one transformer center tapped to provide 120/240 volt single phase and 240 volt three-phase (one of the legs is 208V to ground and doesn't connect to anything except three phase loads). Typically, we've done that for someone who's primary load is a residence, but they want three-phase service to run a compressor or a few machines in a shop out back. I've never done this with services larger than 200 amps, so such an arrangement would be unlikely to have a meter multiplier of anything other than 1.

 

[waross]

It was at one time used for residential services to power large three phase air conditioners.
I have run into a number of old residential services that are now 120:240 Volt single phase but it is obvious that at one time in the past it was a three phase 120:240 Volt delta service.

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