Development Of Array Photoelectric Detector For Space Electric Field Measurement In Transformer Oil

HVDC(High Voltage Direct Current)transmission system has been developed rapidly for the advantages of long-distance and high-capacity transmission.Converter transformer,which is one of the important equipment in HVDC transmission system,its reliability directly determines the safety and stability of the HVDC transmission system.Converter transformer is different from ordinary AC transformer due to its special working condition that Converter transformer not only withstand the role of AC voltage,but also withstand the role of DC voltage and polarity reversal voltage.Therefore,the insulation design of converter transformer is significantly crucial.Currently,the insulation design of the converter transformer mostly uses the electric field simulation calculation method,a few researchers measure the electric field in the oil-paper insulation composite structure by a single point photodetector based on the Kerr effect method.However,there are still some problems that it cannot be measured simultaneously in multiple regions.In order to study the dynamic process and distribution rule of the space field of the oil-paper insulation under DC voltage more accurately,it is urgent to carry out the research of the array photoelectric detection device,so as to achieve the rule of electric field changing with time in area at the same time under continuous pressure.In this thesis,the array photodetector used to measure the electric field in oil based on the principle of Kerr effect measurement has been developed,it has designed the amplifier circuit and analyzed the noise source of the amplifier and reduced the noise gain significantly by using feedback capacitors measurement.And the circuit is tested for consistency,crosstalk and sensitivity.The results of the conformance test show that the photoelectric coefficients of the eight photodetectors were 0.183 A/W,the average variance was 2.4E-06,and the linearity was 0.9999,which verified that the eight photodetectors were highly consistent.Crosstalk test results show that whether one photodetector is illuminated by a single point,or at the same time,two or four photodetectors are irradiated simultaneously,the output voltage of other photodetectors not exposed to light are about 8mV background noise of photodetector.The minimum measurable AC electric field strength is 0.987kV/mm and the DC electric field strength is 0.477kV/mm.The area electric field measurement platform based on Kerr effect method was established by using the array photoelectric detector,A preliminary measurement experiment of the electric field in oil was carried out under the single oil gap and oil-paper composite insulation structure by using the built measuring platform.