Research On Deterioration Performance And Detection Method Of Pressure Sensitive Surge Protector

The pressure-sensitive surge protector is an important over-voltage protection device in the field of power communication,which plays a vital role in the safe and effective operation of system equipment.Long-term work will be affected by external stresses such as lightning pulse and overvoltage,and the core of the ZnO varistor will gradually deteriorate.It is of great significance to study the lightning-induced degradation performance and detection methods of pressure-sensitive surge protectors..The specific research contents are as follows:1)Experimental study on degradation under multi-pulse lightning impulses.Different from the traditional single-pulse impact test,the continuous multi-pulse impact test can more accurately study the parameter variation of the pressure-sensitive surge protector during lightning impulse.The new multi-pulse lightning generator was used to carry out the impact test.The parameters such as the number of pulses,time interval and pulse amplitude were changed to quantitatively study the degradation characteristics of the ZnO varistor from the electrical and thermal properties.The results show that the leakage current of the ZnO varistor will change after multi-pulse shock;the varistor voltage will rise first and then fall,which is different from the downward trend under multiple single-pulse impact;the capacitance value fluctuates within a small range.The undulation is different from the rising phenomenon under multiple single pulse impacts;the surface temperature distribution is not uniform;the length of the pulse interval has little effect on the energy absorption of the sample.The experimental conclusions provide a reference for the development of performance indicators and degradation warning of surge protectors under multi-pulse lightning impulses.2)Prediction model for leakage current and temperature distribution under multi-pulse lightning impulses.Based on the results of multi-pulse simulated lightning impulse experiments,parameter prediction models were established.(a)Based on the irreversibility of leakage current and the adaptability of genetic algorithm and the superiority of solving nonlinear problems,a leakage current fitting model based on genetic algorithm is established.(b)The transient thermal impedance model is introduced to study the net energy absorption of each impact process through the change of heat dissipation.(c)The temperature distributionmodel based on BP neural network is established,and the tripping can be realized by the temperature condition of the surface of the varistor.3)Research on leakage current detection method of pressure sensitive surge protector.According to the current variation characteristics of ZnO varistor under multi-pulse impact,a low-power low-voltage surge protector tester is designed to improve the convenience of detection;Aiming at the problems of traditional capacitive current compensation method under high voltage system,such as harmonic interference of power grid and small application range of phase shift current method,an improved phase shift current algorithm is proposed.The phase relationship is used to solve the capacitive current and extract the resistive component.Through simulation and FFT analysis,the accuracy of online detection is improved.The conclusions of multi-pulse impact test,parameter models and leakage current detection method have laid a theoretical foundation for manufacturers to develop better varistor or develop on-line detection products for surge protectors.