Islanding-operation prevention apparatus, and dispersed power generation apparatus and power generation system using the same

A utility linking system comprising:

• a utility grid;
• and
• a plurality of distribution systems each including:
• a dispersed power supply being connected in parallel to the utility grid,
• a first distribution line for connecting the utility grid to the dispersed power supply,
• detection means, provided on the first distribution line, for detecting a voltage outputted to the first distribution line or an electrical current flowing in the first distribution line,
• breaking means, provided on the first distribution line and situated closer to the dispersed power supply than the detection means, which is capable of setting both a connecting state and a disconnecting state between the utility grid and the dispersed power supply and generally sets the connecting state,
• a second distribution line provided between the dispersed power supply and the breaking means,
• a pulse circuit for emitting a pulse, and
• switching means, connected to the second distribution line, for performing a switching operation in response to the pulse emitted from the pulse circuit,
• wherein said utility linking system further comprises:
• a plurality of control means, each provided to each of the plurality of distribution systems, for comparing each of output values respectively outputted from each of the plurality of detection means with each of output voltage values respectively outputted to each of the plurality of second distribution lines through the intermediary of each of the plurality of switching means, and commutating, in the case where at least one of the comparison results shows a fluctuation which is greater than the predetermined amount, the breaking means provided in the corresponding distribution system from the connecting state to the disconnecting state;
• and
• a plurality of synchronization circuits for setting each number of the pulses respectively emitted from the plurality of pulse circuits each provided in the plurality of distribution systems to a predetermined number.