The chaotic characteristics of time series of five partial discharge （PD） patterns in oil-paper insulation are studied. The results verify obvious chaotic characteristic of the time series of discharge signals and t...The chaotic characteristics of time series of five partial discharge （PD） patterns in oil-paper insulation are studied. The results verify obvious chaotic characteristic of the time series of discharge signals and the fact that PD is a chaotic process. These time series have distinctive features, and the chaotic attractors obtained from time series differed greatly from each other by shapes in the phase space, so they could be used to qualitatively identify the PD patterns. The phase space parameters are selected, then the chaotic characteristic quantities can be extracted. These quantities could quantificationally characterize the PD patterns. The effects on pattern recognition of PRPD and CAPD are compared by using the neural network of radial basis function. The results show that both of the two recognition methods work well and have their respective advantages. Then, both the statistical operators under PRPD mode and the chaotic characteristic quantities under CAPD mode are selected comprehensively as the input vectors of neural network, and the PD pattern recognition accuracy is thereby greatly improved.展开更多
The valve side windings of converter transformers bear AC, DC, impulse, and reversal-polarity voltages during operation, which could result in serious insulation problems of the equipment. By performing experiments wi...The valve side windings of converter transformers bear AC, DC, impulse, and reversal-polarity voltages during operation, which could result in serious insulation problems of the equipment. By performing experiments with surface discharge model of oil-paper insula- tion at 80 ℃ under combined AC-DC voltage for 200 h, we studied the spectrums and statistical parameters of partial discharges at different discharge stages. Furthermore, some fingerprint parameters were calculated in order to estimate the development situation of par- tial discharge, while the characteristic gases dissolved in the transformer oil were measured by gas chromatography. The surface discharges in the experiments were observed using a high speed camera, and a full discharge process could be marked off into four stages as follows. ①The elementary stage. When a partial discharge occurs near electrodes, electrical charges are injected into the region near electrodes and causing bubble generation. ②Due to their high resistivity and low dielectric constant, the bubbles would bare the major part of the voltage applied to samples. Therefore, discharge happens inside the small bubbles, and it emits a lot of light. ③Micromolecules of gas are produced in discharge, and further ionization in the transformer oil takes place simultaneously when high-energy electrons collide with oil molecules. ④The carrier charge moves forward to electrodes driven by the applied electric field, till they neutralize with the charge from electrodes, and hence discharge channels are formed subsequently.展开更多
This paper studies on the Partial Discharge (PD) Locating System based on a mobile array of ultra-high frequency (UHF) antennas and a vehicle-mounted PD locating system is established. The system consists of omni-dire...This paper studies on the Partial Discharge (PD) Locating System based on a mobile array of ultra-high frequency (UHF) antennas and a vehicle-mounted PD locating system is established. The system consists of omni-directional antenna array for receiving UHF PD signals, a pre-processing circuit for signal amplification and filtering and the high- speed acquisition and control unit of PD pulse signals. The developed locating system is able to simultaneously record the PD pulse signals received by the antenna array. By assessing the time difference of arrival (TDOA), the two-dimensional hyperbolic locating model quickly locates the PD source. Based on the software developed by LabVIEW, it is also possible to display, store and further analyze the acquired signals. Through the simulation of PD signals and the locating experiments with the system, it is proved that the PD locating system possesses the features of rapidity and precision in determining the bearing of PD source.展开更多
Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, ...Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, such as repetition rate, magnitude and phase of discharges, which makes them not suitable for intensive studies of discharge process. Therefore, using Simulink code, we theoretically ana- lyzed and studied the classical equivalent circuits of cavity discharges, as well as the influence of circuit components on simulation results, and then proposed a novel equivalent circuit, the key parameters of which were determined according to the physical behavior of cavity discharges. In the novel equivalent circuit, the repetition rate can be changed by discharge resistance, inception and residual voltages; meanwhile the phase of discharge can be controlled by adjusting the parameters of shunt resistance. Furthermore, a controlled current source as a function of space charge is introduced in the equivalent circuit. Compared with the former ones, the simulated signals obtained by this novel model are better approximation of real signals. This work could be referred by latter studies of the characteristics and the me- chanisms of cavity discharge in oil-paper insulation.展开更多
Direct current (DC) partial discharge (PD) test has drawn extensive attention from world-wide electric power research institutes in recent years. However, presently, no DC PD detection device on the market has the sta...Direct current (DC) partial discharge (PD) test has drawn extensive attention from world-wide electric power research institutes in recent years. However, presently, no DC PD detection device on the market has the statistical function. Thus, we developed a test system for PD detection under DC voltage, which is characterized by strong anti-jamming capability, continuous high-speed real-time data acquisi- tion and effective, complete detection of DC PD signals. The DC PD mechanism, as well as the measuring principles, software system, and hardware design of the test equipment were introduced. Adopting typical electrode pairs, we tested the statistical spectrum of PD under DC voltage. The main difference in statistical spectrums between parallel plate electrodes and needle-plate electrodes was that the time interval between two consecutive discharges for needle-plate electrodes has obviously larger variation range than that for parallel plate electrodes, which could be the convincing proof for distinguishing the type of electrodes under DC PD. Practical results indicate that the proposed sys- tem can measure time domain signals of DC PD of oil-paper insulation effectively and promptly, and it can be used to determine and detect defects in DC power transmission equipment.展开更多
A defect of chromatogram in a 35kV oil-immersed three-phase one-piece electric reactor in a 500kV substation。The initial analysis suggests that the defect is caused by the loose connection of the iron core magnet shi...A defect of chromatogram in a 35kV oil-immersed three-phase one-piece electric reactor in a 500kV substation。The initial analysis suggests that the defect is caused by the loose connection of the iron core magnet shield (magnet shield layer of iron core or earthling top). Examination of winding DC resistance, DGA and other relevant examinations were carried out to investigate the defect reasons., which is demonstrated by the dismantlement. In-depth study is taken and corresponding prevention measures are put forward in the paper.展开更多
基金supported by National Natural Science Foundation of China(No.50877064)
文摘The chaotic characteristics of time series of five partial discharge （PD） patterns in oil-paper insulation are studied. The results verify obvious chaotic characteristic of the time series of discharge signals and the fact that PD is a chaotic process. These time series have distinctive features, and the chaotic attractors obtained from time series differed greatly from each other by shapes in the phase space, so they could be used to qualitatively identify the PD patterns. The phase space parameters are selected, then the chaotic characteristic quantities can be extracted. These quantities could quantificationally characterize the PD patterns. The effects on pattern recognition of PRPD and CAPD are compared by using the neural network of radial basis function. The results show that both of the two recognition methods work well and have their respective advantages. Then, both the statistical operators under PRPD mode and the chaotic characteristic quantities under CAPD mode are selected comprehensively as the input vectors of neural network, and the PD pattern recognition accuracy is thereby greatly improved.
基金Project supported by National Basic Research Program of China(973 Program) (2011CB 209400)Program of State Key Laboratory of Power Systems for ±1 100 kV UHVDC Technology(SKLD10M09)
文摘The valve side windings of converter transformers bear AC, DC, impulse, and reversal-polarity voltages during operation, which could result in serious insulation problems of the equipment. By performing experiments with surface discharge model of oil-paper insula- tion at 80 ℃ under combined AC-DC voltage for 200 h, we studied the spectrums and statistical parameters of partial discharges at different discharge stages. Furthermore, some fingerprint parameters were calculated in order to estimate the development situation of par- tial discharge, while the characteristic gases dissolved in the transformer oil were measured by gas chromatography. The surface discharges in the experiments were observed using a high speed camera, and a full discharge process could be marked off into four stages as follows. ①The elementary stage. When a partial discharge occurs near electrodes, electrical charges are injected into the region near electrodes and causing bubble generation. ②Due to their high resistivity and low dielectric constant, the bubbles would bare the major part of the voltage applied to samples. Therefore, discharge happens inside the small bubbles, and it emits a lot of light. ③Micromolecules of gas are produced in discharge, and further ionization in the transformer oil takes place simultaneously when high-energy electrons collide with oil molecules. ④The carrier charge moves forward to electrodes driven by the applied electric field, till they neutralize with the charge from electrodes, and hence discharge channels are formed subsequently.
基金supported by National High-tech Research and Development Program of China（863 Program）（2009AA04Z416） National Science Foundation of China（51021005） Scientific Innovation of Colleges and Universities（Project v-200704）
基金supported by National High-tech Research and Development Program of China（863 Program）（2009AA04Z416） National Science Foundation of China（51021005） Scientific Innovation of Colleges and Universities（200704）
文摘This paper studies on the Partial Discharge (PD) Locating System based on a mobile array of ultra-high frequency (UHF) antennas and a vehicle-mounted PD locating system is established. The system consists of omni-directional antenna array for receiving UHF PD signals, a pre-processing circuit for signal amplification and filtering and the high- speed acquisition and control unit of PD pulse signals. The developed locating system is able to simultaneously record the PD pulse signals received by the antenna array. By assessing the time difference of arrival (TDOA), the two-dimensional hyperbolic locating model quickly locates the PD source. Based on the software developed by LabVIEW, it is also possible to display, store and further analyze the acquired signals. Through the simulation of PD signals and the locating experiments with the system, it is proved that the PD locating system possesses the features of rapidity and precision in determining the bearing of PD source.
基金Project supported by National Basic Research Program of China(973 Program) (2012CB215205)Fund for Innovative Research Groups of China (51021005)
文摘Numerous equivalent circuits for cavity discharges have been developed, yet most of these models cannot provide simulated sig- nals that precisely reveal the variability of the discharge’s characteristic parameters, such as repetition rate, magnitude and phase of discharges, which makes them not suitable for intensive studies of discharge process. Therefore, using Simulink code, we theoretically ana- lyzed and studied the classical equivalent circuits of cavity discharges, as well as the influence of circuit components on simulation results, and then proposed a novel equivalent circuit, the key parameters of which were determined according to the physical behavior of cavity discharges. In the novel equivalent circuit, the repetition rate can be changed by discharge resistance, inception and residual voltages; meanwhile the phase of discharge can be controlled by adjusting the parameters of shunt resistance. Furthermore, a controlled current source as a function of space charge is introduced in the equivalent circuit. Compared with the former ones, the simulated signals obtained by this novel model are better approximation of real signals. This work could be referred by latter studies of the characteristics and the me- chanisms of cavity discharge in oil-paper insulation.
基金Project supported by National Basic Research Program of China (973 Program) (2011CB 209400)State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments (SKLD10M09)Program for ±1 100 kV UHVDC Technology
文摘Direct current (DC) partial discharge (PD) test has drawn extensive attention from world-wide electric power research institutes in recent years. However, presently, no DC PD detection device on the market has the statistical function. Thus, we developed a test system for PD detection under DC voltage, which is characterized by strong anti-jamming capability, continuous high-speed real-time data acquisi- tion and effective, complete detection of DC PD signals. The DC PD mechanism, as well as the measuring principles, software system, and hardware design of the test equipment were introduced. Adopting typical electrode pairs, we tested the statistical spectrum of PD under DC voltage. The main difference in statistical spectrums between parallel plate electrodes and needle-plate electrodes was that the time interval between two consecutive discharges for needle-plate electrodes has obviously larger variation range than that for parallel plate electrodes, which could be the convincing proof for distinguishing the type of electrodes under DC PD. Practical results indicate that the proposed sys- tem can measure time domain signals of DC PD of oil-paper insulation effectively and promptly, and it can be used to determine and detect defects in DC power transmission equipment.
文摘A defect of chromatogram in a 35kV oil-immersed three-phase one-piece electric reactor in a 500kV substation。The initial analysis suggests that the defect is caused by the loose connection of the iron core magnet shield (magnet shield layer of iron core or earthling top). Examination of winding DC resistance, DGA and other relevant examinations were carried out to investigate the defect reasons., which is demonstrated by the dismantlement. In-depth study is taken and corresponding prevention measures are put forward in the paper.
