Need for a Simple AC Current Detector

Sorry, but the concept of a home-brew auto-switching connection to a utility system leaves me cold because it is fraught with danger and potential liability issues. If this is the same thing you posted earlier I'd like to suggest that you purchase a completely integrated module to accomplish your goal, any other way may be dangerous to your system. This site has an interesting array of solar electronics with decent explanations of how they play together.

Thank you for the link. I do not recall having said to use it as auto-switching utility interface. That is not the intention.

Just need a simple alarm to inform the client if his pockets are under stress or not. Most of our clients cannot sit and watch energy monitors. It is the completely (not found) integrated module that I am looking for. But most solar "specialists" just list the classic stuff that you can find everywhere. Most inverters we have here on the rack too.

They sell, just as our company does since 1989 (only installations). Trying to start innovation there, is harsh. Thank you.

The interaction of feeding back to the grid and related safety procedures are taken care of by the inverter, which is UL certificated (to name just one).

Instead of feeding energy back to the grid, for what we are not getting paid for, we want to charge a 338 Volts DC battery bank and use this stored energy e.g at night.

We trick the inverter as we present the battery instead of the panels array when no sun and enough charge available.

This can not serve as a backup for power outage, because the inverter does not produce its own sinus.

This is not done in general. The closest attempt is a system of Outback, but I spare the details. (outback 8048 works on 48 volts)

I know 338 Volts is high. I could lower it to 260 Volts. but then I need MPPT chargers for that voltage, which are not readily available.

The panels are balanced in a way that they cannot over charge the battery. I used deep cycle lead acid, but ordered a Lithium battery setup. The latter saves a lot of space and batteries (3.5 Volts per element)

dvmdsc:

You have to use a current limiting charger along with battery voltage monitoring to stop charging. Simple current sense and trip is not at all a good idea as that may push too high current to battery for a kill. Battery chargers are often properly designed and they also consider input voltage - inrush input current and battery parameters into account. You may end up with explosion in the battery storage room which may be nasty and very dangerous so my clear advise is - not to play with mass charge storage system unless you know everything about it very well.

Thank you for thinking with me. I consider myself recently a member of the "lacking intelligence group" (Lol)

The design takes care of that problem. There is a voltage high and low window protection. The missing link is the current sensing switch. The ones available are for generators and lack sensitivity for our application. How about your travel plans? D

dvmdsc:
The first part is the current limiting design for over current which limits the maximum pulsed or DC current.
The second part is the battery voltage sense circuit which you have.
The third part is the pulsed current / charge injection circuit as DC current is rarely used which may also use current sense circuit to see if current is flowing in the battery and if it is flowing then how much of it is as a function of time. Some time current sense is also used for current limiting the peak current and it need to be of fast response and perhaps to control pulsed MOSFET based charging scheme.

A standard Power Direction Relay is the device you are looking for.

Google can do the rest for you.

Thank you

What you are looking for in most industrialized western cultures needs to be:-

a) licensed by your local electricity supply company

and

b) a unit that has been subjected to many important tests and has been accepted by some country wide authority that checks such units out before letting them on the market for the whole country. The units are seldom cheap!

As far as I am aware,they are all automatic switching, to reduce the possibility of failures induced by incompetent owners....I could be wrong on that score though for your area/county and someone here will know better.

Even certified units and installations still need to be checked by the local supply company (even if of an accepted quality/type from an accepted supplier) so that it is known just how much Solar back feeding is taking place in your area and on a good sunny day, are the supply cables man enough for the job for example?

Some people here have not been allowed to back feed the grid due to old/small supply cables and too much Solar power locally.....boy were they pissed!!!

Also, your electricity meter needs to be of a specific type that counts the amount of energy used/supplied as rarely are you allowed to have the same compensation as you pay per KWH., for example.....

Which often makes payback a 20 year experiment at current compensation rates. The local supply company makes most of the money off the electricity you supply by the way!!!!!! What a surprise!!!! Often 80%......a possible example might be that you pay say $0.25 per power unit, but you only get back $0.05 for those you produce and back feed....

All in all an expensive and frustrating business and if you are small potatoes power wise, probably simply not worth it. You need a few big roofs full of (expensive and still inefficient) Solar cells....plus part of a small but safe room for the control equipment....and of course complete certification (as a word to use!).

Solar cells are constantly being improved and there appears to be some experiments that may make them cheaper and far more efficient in the near future. Whatever type you buy, make sure that they are water cooled (see first link below), as this alone gives you cheap domestic hot water/Heating and it also improves the overall efficiency of the current Solar cells which do not like being too hot!!!! Sadly!!!

Make yourself clever and fully informed and certified (yes that is the right word!) before you spend one red Cent!!!!

Its usually better to just supply your own needs and reduce dramatically your reliance on external power, though using properly certified equipment is still in most countries a must for safety reasons alone....

Please read the following before investing any money just yet, especially the second video in the first link:-

http://www.engineering.com/ElectronicsDesign/ElectronicsDesignArticles/ArticleID/6123/Photovoltaic-Thermal-System-Achieves-86-Efficiency.aspx

http://www.extremetech.com/extreme/168811-new-nano-material-could-boost-solar-panel-efficiency-as-high-as-80

http://www.triplepundit.com/2011/04/4-things-to-consider-before-going-solar-thermal/

Best of luck and let us know what you do, plus a few pictures would be nice.

Just need a detection with switch to know if I am using power from the grid or feeding back to the grid. That can be a non invasive clamp set. And it is of no concern of the power company. I only use it to switch on more load or remove load from the grid.

You could use a small digital power meter, as most can indicate direction of power flow and many come with a configurable output contact.

Is there a reason it has to be a contact? I found a nice single phase power monitor chip from Cirrus Logic that should do the trick nicely. Output E2 will indicate the direction of both the apparent and reactive power flow.

G.A.

I looked into the data sheet and that is a good building stone. However, the idea is to find something ready for use. It will probably come with 2 CT's that fit over the L1 and L2 wires and feeds the "module" with switch.

The contact is the trigger to start charging the batteries, without really disconnecting the inverter from the grid.

Thank you