PURPOSE: To utilize power effectively by feeding power from a system power source or a generator to other loads corresponding to the condition of power flow between the system power source and the generator.

CONSTITUTION: A utility power transmission line 1 is connected through a transformer 4 and a link circuit breaker 5 with a link bus 31. Output from a generator 6 is connected through a generator circuit breaker 9 with the link bus 31 connected with a factory feeder line 11. Other loads 19 are connected through a generator output circuit breaker 12 and a utility power circuit breaker 13 with the link bus 31 and a supply current transformer 14 is arranged at the secondary of the utility power circuit breaker 13. A power flow detection current transformer 21 detects the power flow, and power is fed through the generator output circuit breaker 12 when the power flow from the generator to the system exceeds over a predetermined level while through the utility power circuit breaker 13 when the power flow is lower than the predetermined level to other loads 19.