Research On Automatic Tuning Arc Suppression Coil With Variable Tuning Capacitors Based On Signal Injection Method

Neutral grounding mode in power system related to various dimensions, such as power supply reliability, safety of equipment, personal safety. In most of cities in our country, neutral via arc suppression coil grounding is widely adopted in power distribution system, i.e. the resonant grounding mode.The inductance of arc suppression coil setting is an important key to resonant grounding mode. The resonance matching degree between the inductance of arc suppression coil and lineto-ground capacitance, will affect a series of process, such as compensation effect and arc extinguishing when grounding fault occurring, and initial velocity of voltage recovery after the fault removed. For the issues related to neutral grounding, there are special grounding technology design rules. At present, automatic tracking compensation technique is widely used in arc suppression coil, adjust inductance automatically by measuring line-to-ground capacitance, to meet the requirements(generally in the state of over compensation turning-off degree no more than 10%). The automatic tracking compensation device makes the response of the arc suppression coil more fast and accurate, and the key point is the measurement of lineto-ground capacitance. There are a variety of methods to measurement of line-to-ground capacitance at present, the method of measurement of line-to-ground capacitance manufacturers used may be different, but in general, most of that is by changing inductance value of the arc suppression coil to solve the line-to-ground capacitance.In this paper, aimed at a problem that zero sequence voltage fluctuation in a substation while arc suppression coil tuning, analyze and point out that the reason is to guarantee of measurement accuracy of line-to-ground capacitance by arc suppression coil when it changing its inductance too widely. In order to solve this problem, the injection signal method is proposed to replace the original two points method. Inject special frequency signal into neutral point and extract the special frequency voltage and current by FIR flitter, and calculate the line-to-earth capacitance accurately. In this paper, based on the actual parameters of a substation, make a simulation study, design a proper FIR filter, and give the key hardware circuit.