Research Of Auto-turning Arc Suppression Coil By Switching Parallel Capacitor And Non-solidly Earthed Line Selection Based On The DSP2812

Single-phase to earth fault is the most frequently happened fault form in power system.The probability is up to 70 percents in all forms of faults。The fault current is small and the three phase line to fine voltages are still symmetric while single-phase to earth fault occurs in a non-solidly earthed network, the load can be in normal process for a period of time.But after the fault,the no—faulted phase voltage would increase and intermittent arc grounding would lead arc over voltage,so the insulation would be damaged in long time running leading more serious phase-to-phase voltage fault.So single-phase to earth fault should be removed as soon as possible and the fault line should be found immediately.For the distributed capacitance of the network is the main cause of the fault current,it can be compensated and reduced by installing arc suppression coil(ASC).Especially to the ASC is auto-tuning,the capacitive current of the power system can be totally compensated by automatically regulating ASC's inductive current . Using the function of tracking compensation, the fault current could be reduced to a small active current and the arc can't maintain and will go out soon.Tracking compensation, which could remove the transient grounding fault automatically and greatly reduce the damage of the permanent grounding fault, is a kind of chief technical measures to reduce the loss caused by ground fault.The automatic fault line selection of single-phase to earth fault which could find the fault line quickly could be good for the reduction of the running time of system with fault and also be an critical technical measure of reduction of the grounding damage.Under this circumstance the auto-turning ASC equipment is expected to be installed in the distributions network which can automatically take variation value in zero sequence capacitance in the wake of network changes of topology to compensate fault current when single phase to ground fault occurs.Out of all auto-turning ASC equipment concepts,the method of arc suppression coil that inductance value is changed by switching corporated connected capacitors distinguishes itself as a very attractive option with grounding capacitive current compensating demand.The fundamental effect of novel ASC is no noise,fast, flexible and no rash.In this paper the working principles of the auto-turning novel ASC as well as implementation of the prototype are described.Fistly,the principles of ASC that inductance changes by switching parallel connected capacitors and its compensating characteristic are specified.It is sharply different for switching frequency of each of capacitors of ASC that inductance changes by switching parallel connected capacitors when each capacity is arranged in the past binary manlier.To solve this problem,a new manner is proposed that each parallel capacitor of ASC is arranged in nearly equal capacity.Secondly to ensure ASC automatically to follow the earth capacitive current,there are two key problems which is automatically measurement of capacitive current flowing to ground and identifying occurrence of single phase to ground fault in network.According to two problems,the new method identifying single phase to ground fault is proposed that the equipment monitors zero sequence current directions of very load line in the single source supply distributions under the maximum and minimum rum of arc suppression coil by automatically switching parallel connected capacitors.Following this theory, the novel controller based on DSP2812 is designed to fulfill the job of compensation control.At last, the system module is established and proved according to the practice case of 2kv,2.2kVar and 2kVar capacitors auto—turning ASC that inductance is changed by switching parallel connected capacitors in the lab, And also the sample equipment of the 2kVar capacitors is designed and implemented,as well as its each circuit Triode AC Switch is tested in the lab.According to the results,the system can automatically turning arc suppression coil which is used to generate the switching pulses for thyristors to regulate the inductive current of ASC by switching parallel connected capacitors following the value of automatically measurement , as well as real-time interactive interface parameters based on LCD240*128. The test result has been proved that design of Auto-turning Arc Suppression Coil by Switching Parallel Capacitor and Non-solidly Earthed Line Selection Based on the DSP2812 is reasonable and the process of switching capacitors is rapid and surgeless。...