Adaptive Reclosure Of Transmission Line Based On Wavelet Transform And Approximate Entropy Algorithm

In order to ensure the transmission line operate safely and increase the reliability of power supply, the auto-reclosing has been widely used in electric power system.But the power system and equipment will be brought serious impact when the auto-reclosing reclose in the condition of permanent fault.With the method of wavelet transform and approximate entropy,this paper has discussed the identification method of permanent fault and transient fault in power line.To avoid reclosing on permanent fault coincidence and safeguard security and stability of power systems, a new criterion and method of adaptive reclosing is also proposed in the paper.This paper analyzes and summarizes the main types of fault judging of adaptive reclosing,and indicates the scope of application and the existence of defects.The dynamic performance of the first arc and the second arc and the rekindle characteristics of the second arc are discussed.The impact of the nonlinear characteristics of arc to the voltage fault phase is also analized and EMTP/ATP is used on the fault phase voltage of single-phase transmission line for simulating and analyzing.The transmission line with and without shunt reactor fault terminal voltage waveform is drived out in the paper.This paper uses a DB5 to analyze the fault terminal voltage of discrete wavelet and extracts the high frequency transient components of the fault terminal voltage in the selected frequency range,and a group of approximate entropy of the frequency components of the wavelet detail coefficients at a specific time window is calculated in the paper.In the condition of transient fault,the high frequency components in the time window of the approximate entropy value is large and fluctuates in the number of cycles when the circuit breaker breaks off.The approximate entropy value of high-frequency components is less attenuated in the conditon of the permanent failure.The sums of the ratio of approximate entropy in the two kinds of fault conditions within each successive time window are significantly different.According to the characteristics,the paper proposes adaptive reclosing criterion based on attenuation coefficient.The paper has simulated the fault terminal voltage of single-phase ground fault with different transition,different faults properties and different fault location.Simulation results have showed the feasibility of adaptive reclosing criterion and the effectiveness of adaptive reclosing method based on the criterion.