Research On Single Phase Adaptive Reclosyre Technology For High Voltage AC Transmission Line

Most of the faults occurring on HVAC transmission lines are transient single-phase grounding faults.In order to ensure the reliability of power supply,auto-reclosure devices are used widely.However,auto-reclosure has certain blindness.In order to achieve reliable non-reclosure of circuit breakers when permanent faults occur and avoid the power system being subjected to short-circuit current impact again,it is particularly important to identify the faults before reclosing.For some transient faults with long arcing time,it is possible for circuit breakers to reclose in the state in which the fault arc has not extinguished,so the determination about the extinguishing time of fault arc is also the key to reclose successfully.In this paper,single-phase adaptive reclosure fault identification and the capture of arc extinguishing time for HVAC transmission lines are studied as follows.Firstly,the characteristics of recovery voltage and fault arc after single-phase grounding fault occurring on HVAC transmission lines are researched.The restraining effect of shunt reactor on secondary arc is analyzed,the lower limit of shunt compensation degree is obtained,and the characteristic of the neutral point small reactance is explained.The transient and permanent fault models of transmission lines are simulated by using ATP simulation software,and the characteristics of electrical quantities such as fault phase voltage are obtained.Secondly,the characteristics of the fault phase voltage are analyzed theoretically when single-phase grounding transient fault and permanent fault occur on transmission lines.By comparing the differences between the two fault states,an optimization strategy for fault identification of single-phase adaptive reclosure is given,which samples the fault phase voltage in the first beat frequency period and the difference between the theoretical value and the measured value of the fault phase voltage is used to be divided by the neutral point small reactance voltage.The fault state are identified by detecting whether the ratio is less than the set threshold.After the restoration of line insulation being detected,the switching operation is carried out after a preset delay.Thirdly,the differences of fault point before and after arc extinguishing completely(secondary arc stage and recovery voltage stage)when single-phase grounding transient fault occurs on HV transmission lines are analyzed,and an algorithm for identifying the arc extinguishing time of single-phase grounding fault is given.The differences of absolute value function integral ratio of fault phase voltage before and after fault arc extinguishing are used as identification criterion,the fault arc extinguishing is determined when theintegral ratio is detected to exceed the set threshold for five times consecutively.Finally,the effectiveness of the two algorithms is verified by the simulation of ATP.The results show that the fault identification algorithm which can identify the fault nature accurately is not affected by fault location and transition resistance,and is easy to implement.The algorithm about the identification of arc extinguishing time can control the detection error to about 10 ms,has high recognition accuracy and reliability,and has strong adaptability as a result of being not affected by the actual arc extinguishing time of the secondary arc.