The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon ener...The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon energy 〉 5 keV and duration 10-20 ns has been detected. It has been shown that the x-ray pulse is due to the ＂runaway＂ of electrons from the head of an anode-directed streamer. The estimated maximum bremsstrahlung energy is about 5-10 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operates.展开更多
Under the inflammable or explosive environment, the direct measurement methods by opening up the explo- sion-proof shell of electrical installations were not adopted. So, it＇s impossible to have a quantitative analys...Under the inflammable or explosive environment, the direct measurement methods by opening up the explo- sion-proof shell of electrical installations were not adopted. So, it＇s impossible to have a quantitative analysis on the limit of conducted disturbance for electrical fast transient burst （EFT/B） in such dangerous environments. Transient conducted coupling model, which using EFT/B as its excitation source, can be built based on circuit and electromagnetic field theory. Furthermore, numerical analysis was performed. The results indicate that the capacitive coupling voltage is the same polarity as EFT/B, and is the main disturbance form of conducted coupling in mines. The inductive coupling voltage is reversed polarity with the ca- pacitive coupling voltage, and both peaks appear only in the rising time of EFT/B, which increase with the rising of load resistance. Moreover, the cable coupling voltage on the side of disturbance source is higher than the one on the other side in tunnel. To reduce the common resistance can suppress the resistive coupling disturbance.展开更多
Inverter-fed traction motors,which are employed for electric-multiple-units(EMUs),are subjected to Pulse Width Modulated(PWM) impulse voltage.Impulse voltage has fast rise/fall time and high repetition frequency.The f...Inverter-fed traction motors,which are employed for electric-multiple-units(EMUs),are subjected to Pulse Width Modulated(PWM) impulse voltage.Impulse voltage has fast rise/fall time and high repetition frequency.The failure mechanism of insulation under impulses is different from that of standard 50 Hz sinusoidal condition.Partial discharge(PD) characteristics(discharge number,mean discharge quantity and phase resolved partial discharge(PRPD) pattern) with different frequencies and different rise times of impulse voltage were investigated.The results reveal that discharge number and mean discharge quantity increase,while PRPD pattern moves to the zero of impulse voltage with decrease of rise time.Discharge number and PRPD pattern follow that trend with increase of frequency,the value of mean discharge quantity is similar.Memory effect of the deposited space charges on PD was studied.PRPD pattern moves to the zero of bipolar impulse voltage due to the role of space charges,with increase of frequency and decrease of rise time.It is revealed that available discharge time is prolonged and overvoltage across the cavity increases with augment of frequency,which results in discharge number increasing.Under the condition of shortening the rise time,with the same statistical time lag tL,△V would increase if dV/dt is higher,which results in enhancement of discharge quantity.Discharge number increases with reduction of rise time,because the decreased multiple of td is lower than the increased multiple of dV/dt.Study of PD characteristics and role of space charges is helpful to the exploration of the destructive mechanism of insulating materials under bipolar impulse.展开更多
文摘The results of an experiment on discharges in long atmospheric pressure air gaps at a pulsed voltage of amplitude up to 800 kV and risetime 150-200 ns are analyzed. In the experiment, a radiation pulse of photon energy 〉 5 keV and duration 10-20 ns has been detected. It has been shown that the x-ray pulse is due to the ＂runaway＂ of electrons from the head of an anode-directed streamer. The estimated maximum bremsstrahlung energy is about 5-10 keV. The presence of a maximum in the bremsstrahlung spectrum is due to that the photons emitted by electrons are absorbed by atoms of the gas in which the discharge operates.
基金Supported by the National Natural Science Foundation of China （50674093） the Project of Fujian Provincial Education Department （JA11098）
文摘Under the inflammable or explosive environment, the direct measurement methods by opening up the explo- sion-proof shell of electrical installations were not adopted. So, it＇s impossible to have a quantitative analysis on the limit of conducted disturbance for electrical fast transient burst （EFT/B） in such dangerous environments. Transient conducted coupling model, which using EFT/B as its excitation source, can be built based on circuit and electromagnetic field theory. Furthermore, numerical analysis was performed. The results indicate that the capacitive coupling voltage is the same polarity as EFT/B, and is the main disturbance form of conducted coupling in mines. The inductive coupling voltage is reversed polarity with the ca- pacitive coupling voltage, and both peaks appear only in the rising time of EFT/B, which increase with the rising of load resistance. Moreover, the cable coupling voltage on the side of disturbance source is higher than the one on the other side in tunnel. To reduce the common resistance can suppress the resistive coupling disturbance.
基金supported by the National Natural Science Foundation of China (Grant Nos. 51177136, 50377035)Zhuzhou Electric Motor Company of CSR
文摘Inverter-fed traction motors,which are employed for electric-multiple-units(EMUs),are subjected to Pulse Width Modulated(PWM) impulse voltage.Impulse voltage has fast rise/fall time and high repetition frequency.The failure mechanism of insulation under impulses is different from that of standard 50 Hz sinusoidal condition.Partial discharge(PD) characteristics(discharge number,mean discharge quantity and phase resolved partial discharge(PRPD) pattern) with different frequencies and different rise times of impulse voltage were investigated.The results reveal that discharge number and mean discharge quantity increase,while PRPD pattern moves to the zero of impulse voltage with decrease of rise time.Discharge number and PRPD pattern follow that trend with increase of frequency,the value of mean discharge quantity is similar.Memory effect of the deposited space charges on PD was studied.PRPD pattern moves to the zero of bipolar impulse voltage due to the role of space charges,with increase of frequency and decrease of rise time.It is revealed that available discharge time is prolonged and overvoltage across the cavity increases with augment of frequency,which results in discharge number increasing.Under the condition of shortening the rise time,with the same statistical time lag tL,△V would increase if dV/dt is higher,which results in enhancement of discharge quantity.Discharge number increases with reduction of rise time,because the decreased multiple of td is lower than the increased multiple of dV/dt.Study of PD characteristics and role of space charges is helpful to the exploration of the destructive mechanism of insulating materials under bipolar impulse.
