Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics inclu...Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics including discharge inception voltage, phase distribution and statistical characteristics on polyimide (PI) surface under different impulse waveforms and the insulation life of PI films are studied in this paper. We carry out experiments based on PD and insulation lifetime test systems, using five different types of repetitive impulses, including three bipolar waves and two unipolar waves. The experimental results show that there is little variation in discharge inception voltage under different waveforms, but great variation in phase distribution and statistical characteristics of PD. In addition, insulation life is approximately the same under different waveforms with the same polarity, and the aging rate under bipolar waveforms is larger than that under unipolar waveforms. We explain the differences between the bipolar and unipolar waveforms on insulation life, which can be concluded that the surface charge under unipolar waveform accumulates more significnatly compared with bipolar waveform and decreases the electric filed strength in discharging the air gap and inhibits surface discharge from occurring.展开更多
A surface discharge non-equilibrium plasma model of air–polyimide under pulsed electrical stress is established, byconsidering the reaction of charged particles on the dielectric surface and the secondary electron em...A surface discharge non-equilibrium plasma model of air–polyimide under pulsed electrical stress is established, byconsidering the reaction of charged particles on the dielectric surface and the secondary electron emission caused by thecondition that high-energy particles bombard the material surface. The model defines the chemical reaction of air discharge byusing simplified set of reactions, which greatly reduces the complexity of the model. To avoid the negative value of particledensity in the process of solution, the logarithmic finite-element method is used to solve the model established, so as toimplement the dynamic simulation of the surface discharge process. Also, the temporal and spatial evolution of themicroparameters such as charge and electric field distribution during discharge are obtained, and the reliability of the model isverified by experiments in terms of discharge development pattern and surface charge accumulation. By comparing thedevelopment process of surface discharge under single pulse and repetitive pulses, it can be seen that surface dischargedevelops from needle electrode to ground electrode under both repetitive pulses and single pulse stress, but the relationshipbetween the discharge propagation time under repetitive pulses and pulse repetition rate is a ‘u’ curve, and the inflection pointmoves to higher repetition rate region with the increase of voltage.展开更多
基金supported by the National Natural Science Foundation of China(51929701,52207153)Fundamental Research Funds for the Central Universities(2023JC005).
文摘Accelerated insulation aging problems under high frequency repetitive impulses in power electronic transformers are drawing more and more attention in modern power systems. Partial discharge (PD) characteristics including discharge inception voltage, phase distribution and statistical characteristics on polyimide (PI) surface under different impulse waveforms and the insulation life of PI films are studied in this paper. We carry out experiments based on PD and insulation lifetime test systems, using five different types of repetitive impulses, including three bipolar waves and two unipolar waves. The experimental results show that there is little variation in discharge inception voltage under different waveforms, but great variation in phase distribution and statistical characteristics of PD. In addition, insulation life is approximately the same under different waveforms with the same polarity, and the aging rate under bipolar waveforms is larger than that under unipolar waveforms. We explain the differences between the bipolar and unipolar waveforms on insulation life, which can be concluded that the surface charge under unipolar waveform accumulates more significnatly compared with bipolar waveform and decreases the electric filed strength in discharging the air gap and inhibits surface discharge from occurring.
基金National Natural Science Foundation of China(grant no.51929701).
文摘A surface discharge non-equilibrium plasma model of air–polyimide under pulsed electrical stress is established, byconsidering the reaction of charged particles on the dielectric surface and the secondary electron emission caused by thecondition that high-energy particles bombard the material surface. The model defines the chemical reaction of air discharge byusing simplified set of reactions, which greatly reduces the complexity of the model. To avoid the negative value of particledensity in the process of solution, the logarithmic finite-element method is used to solve the model established, so as toimplement the dynamic simulation of the surface discharge process. Also, the temporal and spatial evolution of themicroparameters such as charge and electric field distribution during discharge are obtained, and the reliability of the model isverified by experiments in terms of discharge development pattern and surface charge accumulation. By comparing thedevelopment process of surface discharge under single pulse and repetitive pulses, it can be seen that surface dischargedevelops from needle electrode to ground electrode under both repetitive pulses and single pulse stress, but the relationshipbetween the discharge propagation time under repetitive pulses and pulse repetition rate is a ‘u’ curve, and the inflection pointmoves to higher repetition rate region with the increase of voltage.
