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

Close... the actual figures are about:
sell solar power for 60cents kwh
buy grid power for 20cents
buy local power for 6 cents (generation portion of grid power)
And yes don't think too hard, it's a 'game', but hey that's the way it is.

So correct, they want to buy the 6cent power when there is enough available, preferably automatically so they don't have to watch the meter and flip a switch when there is excess...and if something varies (i.e. a cloud goes over the solar or the stove is turned on) they aren't buying the 20cent power for something optional.

So what you need is a directional power sensing device. AKA a Reverse Power Relay which is normally used with paralleled generators setups. It trips when a generator tries to become a motor.

It's relatives that own the setup. Modify? Depends what you mean...maintenance or something like sticking on a meter would be fine. Adding/expanding/changing the solar array would require approval/inspection.

Reverse power relay: Something like what we're after but I think they only monitor one circuit? Here we need to combine two circuits. That seems to be the tricky part - combining/summing them. I can't go on the utility pole where the power lines connect together...else I could just put it there beside the bi-directional meter.

The relays normally come in two formats, from what I can see. Single phase for single phase and balanced three phase applications, and three phase for unbalanced three phase applications.

Apparently you need a CT, a voltage connection, and the actually relay. If your power setup is like a conventional house / small commercial installation, all you would have to do is install a suitable insulated split core CT on a phase conductor at the weatherhead.

OR

Mount the CT on one of the phases immediately before or after the bidirectional meter. How does the Bidirectional meter feed the two disconnects on the shop? Is there a gutter that houses the splices for the two shop mounted disconnects? If there is space, install the CT in the gutter or splice box.

Mount the relay assembly in a suitable enclosure and feed it a circuit from the breaker panel.

Obviously you need the shorting switch for the CT secondary leads and appropriate protection for everything else.

Back to the 'E-Mon' types of meters....
Yes, you can install multiple sets of CTs back to one (1) meter. Research time at the website, or call their customer service engineer guys, they used to be happy to provide any help that I required.

It actually sounds like a great idea, but I don’t think that type of system exists as you described. Probably because it wouldn’t benefit the electric utility companies directly. I’m wondering if you did manage to make your own system like that if the POCO would even let you interconnect it to their grid system without their approval.

If it on the owner's property, would the PoCo even have any say in it? Assuming the owner's electrician does not have to break any PoCo seals to perform the work safely. As it stands right now, the owner can manually turn their optional load on and off manually. All they want to do is automate the process. All they are doing is replicating the PoCo energy meters' information and using it to control loads.

sprdave,

Questions about the physical installation.

1) Where is the bi-directional meter mounted? On the power company owned pole or on the property owner's structure.

2) How and where do the wiring between the two shop drops (solar and PoCo) tie together?

3) Can you get legal physical access to one or both of the phase conductors either before the bi-directional meter or after the bi-meter but before the splice that leads to the two service drops? Not to make any electrical connections, but rather to install split core current transformer(s).

Reasoning:

All the customer really wants to do is automatically turn on a load when he is a net exporter of PV generated power. If the distribution wiring is on the property owner's property, I believe he can do whatever he wants AS LONG AS IT IS ACCEPTABLE to the authorities having jurisdiction. Assuming he is not stealing power, causing actual or potential damage to the utility's equipment, trespassing or any other criminal activity, I do not see an issue.

What he wants to do is duplicate the information that the power company gets in real time. He is not asking for the power company to provide it to him, using their equipment. He is looking to be allowed access to safely install non-intrusive monitoring equipment.

DISCLAIMER

I am not a Canadian resident, lawyer, or even a licensed electrician. My advice is worth exactly what you paid for it, absolutely nothing.

I don't know, I'm not sure how things like that are handled up in Canada. I’m not trying to quash the creative juices, because I really do think it’s good idea, but I am just assuming that unless he can somehow utilize an existing approved net metering setup for this purpose, then he will either have to otherwise be able to interconnect with the utility meter directly or install CT’s ahead of the POCO meter and they do tend to get touchy about things like that, at least around here. If somehow the inspector ends up getting involved, unless the assembly has some sort of NRTL listing, I can see him possibly having issues with it. I don’t think that should stop the OP from trying though.