ECN Forum Forums General Topics of the Trade General Discussion Area metering (net) and load shedding application

Yes, yes it does.

What exact make and model inverter is installed? Does it have or can you add a real time KVA output monitor.

Basic work around would be adding a current monitoring relay to one leg of the inverter output and have it trip when the current exceeds 12.5 A(3 KW) and opens up when the current reaches some lower limit you decide.

These relays are often used on belt driven fans to determine remotely if the fan has a mechanical failure or the belt broke.

This setup will allow the load to only operate when the inverter is putting out current.

Would it make sense to approach the power company and have them change it to a true net metering setup? No more complicated billing methods and make it simpler for everyone?

They are two 5kw Aurora inverters. You can plug in a laptop and/or get monitoring for them, but expensive.

The problem with that or a current relay (and main issue here) is that only goes by the generation. It does not factor the consumption. The inverter could be putting out 3kw, but they could already be consuming 4kw and thus not want to run the extra load.



NO actually. The usual method is now parallel. That means that they buy 100% of the power they consume at normal rates (20cents in the example), no 6cent power if they use it direct.
Net metering is even worse. That means no 60cents for the generation. It would just replace 20cent power.

Thanks for your thinking...eventually something might materialize

I was thinking about it, almost would be tempting to re-route the solar/generation wiring through the load/consumption splitter, so the solar and load wires could be together and put a large CT over them all...Then the CT or current relay would measure the "net" current...

Except that would be a lot of work and they wouldn't like that....

But thinking that, would it be feasible to put individual CTs over each wire (one on each phase of the generation and the consumption) and run the CT secondaries through something like a current relay, to measure the "net" of the CT secondaries??

That doesn't give watts, but might be a compromise.

I think that would work.

1) Wire the same ratio CTs from the same phase in opposing series so that the output equals Generation minus Consumption.
2) Swap the polarity of the Red leg from the Black leg so that the outputs from each leg are now in phase with each other.
3) Run a single wire from each of the leg CT secondaries thru the Current monitoring relay. That is a total of two wires thru the current monitoring relay sensor coil.
4) Summation of (Generation - Load)red phase + (Generation - Load)black phase. When the result is greater than zero, then the property is producing a net excess of current.

ASSUMPTIONS

1) You don't need to know actual KW values. You just want to know when the property is exporting excess energy.

2) The current monitoring relay IS polarity sensitive AND it can tolerate prolonged "reverse" currents.

3) Reverse current is defined as the current it will see when consumption is greater than generation.

My point was simply that if the system with the control configuration setup that you are looking for existed, you wouldn’t need to be trying to make it work the way you want yourself. Don't give up on it though.