| Mineral insulating oil as the main liquid insulating medium of high voltage electrical equipment has been widely used in power system.With the increasingly stringent requirements for environmental protection and fire protection performance,ester liquid dielectrics have been applied to the insulation of power equipment.At present,ester insulating oil represented by FR3 is regarded as one of the possible substitutes for traditional mineral insulating oil because of its good biodegradability,high ignition point and non-toxicity.The study of the insulation properties of new insulating oils is of great significance for the safe operation of power equipment and power systems.The operating experience of power systems at home and abroad shows that power equipment is subjected to various short-term surge voltages while withstanding long-term operating voltage.Therefore,it is important to understand the insulation performance of insulating liquid under short-time surge voltage.In this paper,the development characteristics of two kinds of insulating oils?mineral insulating oil KI25X and vegetable insulating oil FR3?under the positive standard lightning impulse voltage,the influence characteristics of different flow injection modes and their breakdown characteristics on insulating oil are studied,and the destructive properties will be destructive.The effect model is applied to insulation oil breakdown prediction as an evaluation tool for insulation performance.The main work of this paper is as follows:?1?The impact voltage test platform for the observation of the development speed and breakdown characteristics of the flow in the insulating oil is constructed.Considering the positive lightning impulse voltage,the insulating oil has a lower breakdown voltage and acceleration voltage.The lightning impulse is used as the test voltage waveform.At the same time,this test mainly evaluates the material properties of the insulating oil,so the test electrode is selected by needle-plate electrode.The test platform uses a capacitive voltage divider to record the voltage waveform of the insulating oil gap during the discharge process,and uses the photomultiplier tube?PMT?to record the optical signal flowing during the discharge development process,and uses a high-speed camera to capture the shape during the development of the flow injection.?2?The flow development and breakdown characteristics of the mineral insulating oil KI 25X and the vegetable insulating oil FR3 oil during the gap breakdown process were compared.First,the 10 mm,30 mm,and 48 mm needle plate gap volt-second characteristics of the mineral insulating oil KI 25X and the vegetable insulating oil FR3 were obtained.Then,according to the relationship between the gap distance and the breakdown time,the average development speed of the flow injection during the gap breakdown process is calculated,and the acceleration voltage corresponding to the fast and slow flow development mode under different breakdown voltages is obtained,and the two parameters-Weibull are obtained.The distribution of breakdown probability and 50%breakdown voltage of two insulating oils at different gap distances were obtained.Finally,mineral insulating oil KI 25X and vegetable insulating oil were obtained from 50%impact breakdown voltage and acceleration voltage.Differences in flow development and breakdown characteristics in FR3.?3?Attempts were made to investigate the insulation oil gap breakdown characteristics and discharge delay prediction using the destructive effect model.Through the calculation and calculation of the breakdown test data obtained by the test,the disruptive effect model equation DE???,0,,?of the needle-insulated oil gap under the standard lightning impulse voltage is obtained,and predicted according to the DE model equation.The breakdown time of the needle plate insulating oil gap under the standard lightning impulse voltage is compared with the test data.The main influencing factors of the prediction model are analyzed. |
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