SYSTEM INTERCONNECTION POWER UNIT

PROBLEM TO BE SOLVED: To prevent a short circuit current from flowing in an electric power system from a system interconnection power unit when short circuit is generated in the system. SOLUTION: A DC power source 2, an electric converter 3 converting DC power from the DC power source 2 to AC power, and a system interconnection protective device 4 which detects abnormality of an electric power system 6 connected with the electric converter and generates a signal for cutting off the output of the converter, are installed. The protective device 4 consists of a system abnormality detecting relay 4a which has a previously set specific operation time limit and operates, and a high speed short circuit detecting relay 4b which detects at a high speed a short circuit accident of the connected electric power system and operates. A high speed cutting off means is installed which breaks the output of the converter 3 at a high speed when the relay 4b operates.