PURPOSE: To promote operational reliability by providing a solenoid valve, providing a timer to measure an operating time of a circuit to operate the solenoid valve and a switch, and performing arithmetic of the timer's information and pressure information of a gas insulation apparatus by an arithmetic device.

CONSTITUTION: When a solenoid valve 18 is opened, a pressure difference occurs between a pressure chamber 16 and a switch chamber 17 in a case 11 of an impulse pressure relay 2, a diaphragm 12 is displaced, and a switch 13 is operated. When the solenoid valve 18 is closed by interlocking with an operation of the switch 13, the pressure balances again, and the diaphragm 12 returns to an original state to reset the switch 13. Time to be required from operation to reset of the switch 13 is recorded by a timer 6 and is sent to an arithmetic device 7. While, a temperature of a charged gas 4 is sent to the arithmetic device 7 by a temperature sensor 5 provided to a gas insulation apparatus 1. The temperature of the charged gas 4, the time to be recorded by the timer 6 and an operating characteristic range in a normal state memorized in a memory 8 in advance are operated by the arithmetic device 7, and the operating characteristic is automatically determined.