Based on its characters and principles of transduction

fiber Bragg grating（FBG） is used in insulative fault detecting of electrical devices.Heat always transfers before insulative fault arises in electrical devices;FBG is very sensible to temperature;it is used by monitoring the temperature to monitor whether insulative fault occurs in electrical devices.The test result shows that it has high anti-jamming ability

and it can work under complicated environment.It may work better than traditional sensors when the resolution of temperature is（0.1 ℃）.A method of inspecting faults in high-voltage devices by monitoring the temperature is introduced

and functions and applications for on-line watching systems of high-voltage equipments’ faults are expatiated.