Research On Adaptive Reclosing Of UHV Transmission Line Based On Arc Characteristics

Because of its long distance,large capacity,and low loss,UHV transmission lines have become the optimal transmission channel for energy transmission in resource-rich regions.With the proposal of the “five horizontal and five vertical” UHV pattern,more UHV AC/DC transmission lines were used for cross-regional power transmission.However,due to the fact that the faults caused by the circuit being exposed all year round and affected by many uncertain factors cannot be ignored,the adaptive reclosing technology to ensure the reliable rectification and stable operation of the faults has become the research focus.Based on the characteristics of arc at the fault of UHV single-circuit and double-circuit transmission lines,this paper presents a method to determine the type of fault and capture the time of arc extinction.The high-frequency voltage energy for distinguishing the fault type and the local flatness for arc extinguishing determination are extracted by the fault phase voltage spectrum analysis.At the same time,combined with the characteristic harmonic distortion rate and the frequency distribution properties of all types of fault features,an improved decision method is proposed to improve the accuracy of fault identification and arc extinguishing status determination.Firstly,this paper analyzes the common methods of fault determination and arc extinguishing determination for single-circuit and double-circuit lines at the present stage,and determines the method of using fault-phase transient voltage spectrum information based on arc characteristics to determine the fault and extinguish the arc.Based on the theoretical analysis of primary and secondary arcs,the ATP-EMTP electromagnetic transient simulation software is combined with the TACS and MODELS module to complete the arc model for transient and permanent faults,and it is loaded to a single return based on actual UHV.Simulate fault status in a simulation model with two-circuit line parameters.By comparing the instantaneous arc fault and the secondary arc simulation arc resistance dynamic waveform diagram,it shows that the arc simulation model characteristics are consistent with the arc theory characteristics.By comparing the instantaneous and permanent fault phase voltage simulation wave-forms,it is shown that both arcs can simulate the effect of the actual arc on the fault phase voltage.Then,based on the pull transformation of the equivalent model of single-circuit and double-circuit UHV transmission lines,the theoretical analysis shows that the fault-phase coupling voltage in the secondary arc stage is mainly affected by the spectrum characteristics due to the arc characteristics,and the fault phase recovers from the voltage phase.The voltage mainly contains the fundamental frequency and the free component.Based on the above theory,it is proposed to take the secondary arc of the two transmission line transient faults,the recovery voltage phase and the fault phase voltage after the trip of the permanent fault circuit breaker as the research object,through the ap FFT all-phase fast Fourier spectrum analysis.The algorithm studies the frequency distribution and obtains the characteristic frequency bands that can be used to distinguish the fault type and the characteristic harmonic frequencies used to determine the arc state.Secondly,when a single-phase earth fault occurs in the UHV Long South I line and the UHV E Yue I and II line simulation models,high-frequency energy values are obtained by extracting fault identification characteristic frequency band voltages,and a qualitative comparison is made with the determination threshold values.There is an error in the result and the threshold is affected by multiple factors.Furthermore,an improved fault determination method is proposed based on the decision feature consisting of high frequency voltage energy ratio and characteristic harmonic distortion ratio combined with SVM.Judging results show that this method is not affected by the fault location,transition resistance,power supply potential angle,shunt reactor compensation degree,line transposition method,etc.The judgment accuracy is high,and the fault determination of adaptive reclosing can be achieved better.Finally,after the determination of the actual line fault type is completed,according to the local flatness characteristics of the dense spectrum,the frequency local arc flatness value of the transient fault phase voltage characteristics is extracted as the arc extinguishing determination feature quantity.When the characteristic amount is less than the arc extinguishing determination threshold within two consecutive cycles,it is determined that the arc is extinguished.Among them,the arc extinguishing determination threshold is obtained by studying the influence of multiple factors on the characteristic quantity of arc extinguishing determination.In order to solve the problem of determining the frequency of frequency characteristic leakage of the arc extinguishing characteristic of the local flat characteristic,the 8-dimension local flatness vector is extracted by using the frequency distribution characteristic of all types of fault state characteristics as the arc extinguishing determination feature quantity,and an improved arc extinguishing determination scheme is proposed in combination with the SVM.The results show that the arc extinguishing determination method is improved,and the arc extinguishing determination of the adaptive reclosing is well achieved.