Study On The Online Monitoring Of Contaminational Leakage Current Based On LED Optical Fiber Current Sensor

Preventing the polluted electrical equipment of transformer substations andtransmission lines from flashover has been a key part of the electric power operationwork, in order to prevent pollution flashover happening, the contamination of theelectrical equipment need to be tested, the best way was concentrated on real-timemonitoring of the surface contamination of the insulator, the result can reflect thedynamic situation of the surface contamination of the insulator. Along with the smartpower grids become more and more popular, optical fiber current sensor with itsexcellent electrical properties gradually are applied into power system, which is betterthan electromagnetic sensor, and using optical fiber current sensor(OFS) to testcurrent in the power system has become the most promising and the most activedevelopment direction.Leakage current measurement is an important basis of the work for preventingelectrical equipment from dirt flashing, the fiber optical current sensor were used inon-line monitoring system in electric power system, this made many advantages, suchas, light weight, compact structure, easy multiplexing, high resistance to terribleenvironment, electromagnetic interference and chemical corrosion, no power but longdistance distributed sensing, and low cost mass production. All these advantagesbrought the optical fiber current sensor into electric power system, which has the vreyimportant significance. Therefore, single-track half wave LED optical fiber currentsensor (SH-LED-OFS) based on LED was designed and produced in this paper, whichcould detective the positive and negative half cycle of the leakage current, then someimprovement was did based on it, from analysis of the working principle andoptimization design processing circuit, the two-way whole wave LED optical fibersensor (TW-LED-OFS) was completed, all these were laid a foundation for using ofoptical fiber sensor for current leakage current online monitoring.These sensors took advantage of the luminous characteristics and thecharacteristics of single guide of the light emitting diode (LED), and use an LED asdetection equipment for the leakage current, by designing its circuit reasonable, LEDhere was used to convernt current into light signal, and then the combination circuit ofthe amplifier and slicon detector complete photoelectric conversion, in this way, thesensor has selectively measure leakage current positive and negative polarities current wave. Tests show that, the sensor’s response degree could achieve to40mV/mA,detection band was about1～10kHz;. Along with some optimization, the two-waywhole wave LED optical fiber sensor (TW-LED-OFS) used two LEDs to detect thepositive and negative half cycle of the current, and a differential circuit was used toprocess signal, which could combine the positive wave and negative wave, and thenobtain full waveform of the leakage current. After test and analysis for thecharacteristics of TW-LED-OFS, the results showed that the sensor based on LED canachieve selective measurement for some half cycel or a whole wave signal, the sensorcould collect first-hand material of the contamination conditions, which lays substantialfoundation for the evaluation and forecast for pollution flashover.