I have only heard the phrase ?reverse power? used in the context of two or more power sources that are operating in parallel, and that are thereby sharing the load. Once they are connected in parallel, their frequencies and voltages will necessarily be locked into synchronization. If the paralleled sources are generators, then you change the amount of load being carried by any one machine by using the controls that would raise or lower its frequency or its voltage, had it be operating independently. If you lower these controls too much, it can cause power to flow into it from the other machines. That can be harmful. If a generator that is in parallel with others experiences an internal fault, then the others will send vast great deals of energy into the faulted machine. That can be very harmful. The paralleling gear to which the generators are connected, or the generator breaker controls themselves, will have relaying systems designed to trip a generator off line, should it be receiving power from the other parallel sources.
You can also see a reverse power condition when two or more transformers are operating in parallel. You won?t have any frequency or voltage controls for transformers, of course, so the degree to which they share the load will depend mostly on their internal impedance values. Here again, if one transformer experiences an internal fault, then the others that are in parallel with it will feed energy into the fault point. Two or more transformers in parallel would be commonly called a ?transformer network.? The device that is used to protect each transformer against a reverse power condition is called a ?network protector.?
