Here's a question I've had for a long time. I've read of people who generate their own electrical power with various means and sell the excess to the utility company. Somehow they are pumping their excess power into the utility grid. How is this done? How can a small generator pump his electrons "upstream"? Wouldn't this be like trying to add water to the city's resevour by pouring a glass of water into a fire hydrant? The pressure would cause the water to flow the wrong way.
Thanks, Tom
Actually they have backflow preventers in fire hydrants, and all other "city" water supplies for exactly that reason. If the pressure (aka voltage) is higher, the current will flow up stream. Most meters will run backward if this happens but when you do have the proper severse energy system this is done a little more "officially". It requires the correct metering equipment plus the proper charge controller in the alternate energy interface to the service.
Most electric meters will not run backwards any more. They fixed that like
15 years ago when people were turning the meters upside down and letting them run backwards to lower the bill. I am sure there are a few ancient ones out there somewhere but most have been change out years ago.
There's even another twist to this. One form of hybrid meter?induction disk with electronic register?uses photoelectric means to count dark/light markings on the disk. In that case, delivered AND received power both increment the single [delivered-power] register.
?s falke
If you generate a fractionally higher voltage than the supply voltage, you will feed the supply. In the UK, electricity suppliers are required to allow domestic customers to do this and they pay the customer for the energy fed back, as part of a government scheme to encourage alternative energy sources. It requires changing the metering equipment, and in the one example I've seen, the metering was all electronic and includes all sorts of safety features too, such as making sure you don't backfeed if the mains supply has failed, nor connect your installation whilst self-powered to the supply unless the phase is in sync. I suspect deployment is very thin on the ground at the moment. I don't know who is expected to pay for the metering equipment.
I believe that voltage is not a main issue here. If you imagine a electrical motor (of any kind) connected to the grid, and with mechanical power increase its original speed, you will feed the supply in that case. If you invest mechanical power, you will get electrical (very simplified, but the main fact here). Behaviour of the voltages in this case is consequence, not a couse.
___ Broken English is better than a broken leg
Well, you're both right.
If a motor is forced faster than its synchronous speed, power will flow back into the line. But a solid-state inverter, such as those used by home PV setups doesn't have a mechanical input, its all electronic. By sensing the supply frequency and phase, and triggering the electronics correctly, power can be made to flow into the grid. But for that method to work, the inverter must have a voltage higher than the AC sine wave (at least some parts of the cycle).
daestrom
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