High Sensitive FBG Sensor for Equivalent Salt Deposit Density Measurement

Abstract

Online monitoring of the contamination condition of power transmission line is important to prevent insulation from flashover. The conventional online monitoring methods are easily disturbed by the strong electromagnetic interference around the high voltage line. In this letter, Bragg wavelength of polyimide coated fiber Bragg grating (FBG) is found to be slightly restrained by the salt deposited on the polyimide surface. Based on the effect, a special designed FBG sensor is proposed for detecting equivalent salt deposit density (ESDD) on insulators of power transmission line. To improve the sensor sensitivity, multiple polyimide layers are coated on the naked FBG, and in the curing process a 0.15-N force is applied on the free end of FBG to form uniform layers. Experiment results show the restrain wavelength varies with the ESDD. The resolution can be improved with multiple polyimide layers.

Fibre Bragg Grating Sensors for Condition Monitoring of High-Voltage Assets: A Review

“…However, in the presence of salt fog, the salt re-absorbs the water from the PI layers, leading to a reduced wavelength shift of the FBG sensor. Lab tests of a FBG sensor mounted on a ceramic disc in a humidity chamber (95% relative humidity) with repeated salt fog sprays show that the Bragg wavelength is affected by the equivalent salt deposit density [153,154]. The effect of salt deposits is not the same at different humidities and more work is required to determine the response of PI-coated FBG sensors in actual environmental conditions.…”

Review on fiber-optic sensing in health monitoring of power grids

“…An FBG sensor for detecting ESDD on insulators of power transmission lines was reported. 178 By additional polyimide layers, FBG is sensitive to humidity and salt. An optical intensity attenuation-based ESDD monitoring system was carried out in real transmission lines.…”

Optical sensing in condition monitoring of gas insulated apparatus: a review

“…where λ B is the centre wavelength of FBG, n eff is the effective refractive index and Λ is the grating period. When the external conditions cause temperature or stress variation of FBG, the effective refractive index and the grating period will be affected by them [21]. Therefore, it is possible to monitor the change of the temperature or strain by recording the change in the Bragg wavelength of the reflected light, according to (4).…”

“…In the FBG sensor design, different sensing objects such as PD, acoustic, gas, force, wind, humidity etc. are converted into the temperature or strain variation with sensing objects [21][22][23][24][25][26][27][28]. Then, the sensing parameters can be calculated based on the measured Bragg wavelength.…”