Feeding back into the grid??

[John White]

I read about people having solar systems and have excess energy and feed it back into the grid and even getting a check. I am curious as how they synchronize it with the power co. line?. Wouldn't this be the same as just hooking your generator into the grid. And I know definitely not to do that. Wouldn't it be about the same thing as hooking two 3000w generators and making 7000wt. I have read that there is a way but very complicated and can lead to a disaster.

 

[KTurner]

Grid Tie Inverters are designed to synchronize their output to the grid.

 

[dodge man]

Yeah, I don't think its as complicated as you think. I did some work for someone that had solar that fed into the grid when they were making excess power. I think the power company worked with them and it wasn't that tough.

 

[TnAndy]

The reason you don't connect a generator directly to the line is for that reason.....feeding 120 or 240v back on a line, thru a transformer, will step it up to whatever several thousand volts are on the other side of the transformer.

ALL grid tie inverters have to meet UL Standard 1741.....which means unless they 'sense' grid power is on to back feed TO, they shut down. This prevents back feeds that could harm someone down the line working on it. It also means if you have a pure, grid tie only wind or solar power system, when the grid goes down, you are down as well. But when the grid is up, AND the system is producing power, it flows either to the house first, if needed, or back thru the power company meter, out to the grid. It's quite seamless and easy to set up actually.

There are 'hybrid' inverters with battery backup that disconnect from the grid when grid is down, but have an internal transfer switch to allow the power being produced ( or from batteries ) to flow on to the home/etc. You also need a regular transfer switch in most cases, just like you would with a generator, to take your house circuits off the grid as well. That is the way I set my system up.

 

[John White]

Thanks: I always wondered how they did it. Since we are on the power discussions. Look at all supposedly free power generators (free electricity) on u-tube. How can they say they work? Sometimes I think those ads are like the one they had about 40 years ago on "Canid Camera". This guy drives up to a gas station in a VW and fills his gas tank from a water hose and drives off. Is sort of interesting to watch them show you how you can have free electric though.

 

[JakeBrake]

A few large $$ high dollar $$ stationary generator installations feature closed transition automatic transfer switches.

The ATS monitors the commercial power and at the appointed time will start the generator(s). the ATS synchonizes the generator output to the commercial output and when the two outputs are within 5% will transfer the load from commercial to the generator(s). This is a seamless transition and, usually, the lights will not even flicker.

The process is reversed to restore power to commercial and off the generators(s)

This is very useful for fully load testing the generators and switch gear.

This set up can also be used for load sharing or load shaving between commercial power and generator power.

When commercial power fails or is off for any reason, the closed transition ATS works like an open transition ATS.

 

[TnAndy]

. Since we are on the power discussions. Look at all supposedly free power generators (free electricity) on u-tube. How can they say they work?

They can claim anything......getting something to work is a whole different story. Most of those are simply trying to separate people from their money schemes.

 

[Industrial Toys]

One power generation guy told me they use a thing called a "Freq" to put a power plant on line.

Another friend told me how to sync up generators. Forgot somewhat but basically you have a resistor hooked between them at first and watch the current. When it goes to zero, you make the final total connection. It's not that hard. From then on, they will not go out of sync.

The inverters used for home power generation do all manner of automated processes including and obviously, the syncing up of the wave form before connection. I believe the waveform of any system that is supposed to put power back into the system has to lead the waveform of the utility just slightly and also have more voltage then the utility.