Because transmission and distribution equipments of the electric power system long-term exposure under natural conditions

insulating surface of the electrical equipment is easily degraded

which may lead to fault of transmission line.A fiber Bragg grating（FBG）temperature sensor protected by insulators is developed to detect the common heating parts of electrical equipment

the outer surface of the fiber is coated with single-or multi-chip insulators of silicon rubber material

and the sensor is processed by RTV silicon rubber material forming one structure.Insulators protecting the fiber

the sensor can achieve the detection of high-voltage electrical equipment.When the sensor detects the temperature of the electrical equipment

the temperature change of the measuring point will cause the reflective wavelength shift of FBG.Performance test on the FBG temperature sensor protected by insulators is done.Thermostatic bath heating and mercury thermometer of national two level precision as measuring standard are 20 times heating experiments on sensor is carried out from 20 to 90 ℃

wavelength is recorded once while temperature is increased by 10 ℃.Experimental results indicates that the temperature sensitivity coefficient of the senor is 10.2 pm/℃

the linearity is 0.70 %FS.