Backfeeding

[Alwayslearningelec]

Can someone explain this with some examples...:-?

Thanks

 

[readydave8]

backfeeding is current traveling in an unexpected direction or from an unexpected source:

feeding a circuit breaker from the load side so that when it is on the busbar is hot. if its fed from a portable generator during a power outage its not good for the lineman, and they have been killed this way.

 

[augie47]

One use of the term applies to "feeding" a circuit breaker on the terminals we normally consider to be "load" terminals. For example, taking a Main Lug Panel, installing a 100 amp "branch" breaker and suppling the panel by connecting incoming power to that breaker.

Incidentally 408.36(B) prescribes steps to be taken when doing this.

 

[kingpb]

Can someone explain this with some examples...:-?

Thanks

This is very common, and normal in the power industry whereby you utilize the HV substation or switch-yard for power needed to start the auxiliary power system loads, in order to start the generating unit; done when the generator is connected to the system through a generator breaker and there is not a separate station service transformer.

It is accomplished by keeping the generator breaker closed, and feeding power to the auxiliary power system through the step-up transformer, (in this case step down) and then through the auxiliary power transformers to the loads. When the unit is up and running at synchronous speed, you can close the generator breaker upon synchronization with the system, thereby the generator now provides power simultaneously to the loads, and the excess to the system.