Study On Full Fault Current Compensation And Adaptive Reclosure In Distribution Network

Automatic arc-suppression compensation and fault location,isolation and service restoration (FLISR) are two important aspects of self healing and effective ways to guarantee the power supply reliability in distribution network. Now the arc-suppression compensation technology maily refers to automatic tracking compensation of the arc-suppression coil. It can compensate off the power-frequency component of the single-phase grounding fault current. But distribution power system’s expanding and nonlinear load’s growing make the harmonic and aperiodic components of the single-phase grounding fault current increase, resulting in large residual current after power-frequency compensation. This may lead to the failure of compensating arc suppression, which can cause more serious fault. In power distribution network, FLISR is executed mainly by the Feeder automation (FA) technology which does tentative reclosure regardless of fault nature. When reclose to permanent fault, system will suffer from short circuit current and voltage sag again. Power recovery time will also get prolonged, which is adverse to the power supply reliability of distribution power system. Therefore, research on novel arc suppression compensation method and FA scheme to improve the operation security and the power supply reliability of distribution power system has very important significance.In this paper, on the basis of predecessors’ research work, analyze the short circuit faults of distribution power system and propose a full fault current compensation method and adaptive reclosing schemes. Firstly, based on the fixed-frequency signal injection method, calculate the equivalent grounding capacitance of distribution power system and three signal injecting schemes are designed from practical application, that is inject signal at the secondary side of arc suppression coil (ASC), at secondary winding of bus-bar potential transformer and at the neutral point of shunt capacitor bank. To improve the detection accuracy of injection signal, analog and digital filters are designed. Laboratory simulations and field tests validate the above computing method for equivalent grounding capacitance of distribution power system, which provides basis for precisely calculating the full fault current of single-phase grounding fault.After analyzing and proving that r circuit and Π circuit have equivalent external characteristic under certain frequency band, use double r circuit to model the fault line, forming the zero-mode network of single-phase grounding fault. Then the full fault current is approximately estimated in S domain. Send the calculation result to the SPWM modulation inverting equipment and wideband current used for compensation is generated. And complete the full fault current compensation together with the ASC automatic tracking compensation technology. Simulations verify that the proposed full fault compensation method has better compensation effect than common power-frequency compensation.When phase-to-phase fault occurs, line-head breaker tripping off, a small voltage signal is injected between the fault phases. Then calculate the equivalent input impedance by the distribution characteristic of injection signals between the fault phases. Comparing the calculating results, phase-to-phase fault nature can be identified. According to different calculation form, phasor calculation method and instantaneous sampling value based calculation method are proposed respectively. Adaptive reclosure of distribution power system is done by the fault identification result. Combining with A-V and B type FA systems which are widely used currently, adaptive reclosure schemes with and without communication are proposed and both specific implementation process are analyzed. Simulation cases validate the proposed fault nature identification method.Full fault current compensation method and adaptive reclosure schemes presented in this paper can effectively reduce the single-phase grounding fault residual current after compensation and shorten the power recovery time of phase-to-phase fault, which is of great significance to improving the operation security and the power supply reliability of distribution power system.