Study On The Breakpoint Diagnosis Method Of Grounding Grid Based On Magnetic Source

Grounding grid is an important part of the power system. With the rapid development of society and the transmission and distribution networks being bigger and bigger, power load is also increasing increased. High and Extra High Voltage even Ultra-high Voltage transmission distance is gradually available. When the system is subjected to lightning and shorted to ground, a fault current is also increasingly. At the same time, Potential of grounding conductor also will endanger the stability of the system and personal safety as well as a sharp rise of Short-circuit current. To prevent the occurrence of such a major accident and protect the security and stability of the operation, performance of grounding grid becomes more important. Thus, the technology of detecting that whether there is a breakpoint of ground grid has become the focus of the study.This paper studies the breakpoint diagnosis problem of the partial branch of grounding grid. Through in-depth study of the grounding grid fault diagnosis theory, analysis of the grounding grid breakpoints diagnostic Problems of the electricity network method and electromagnetic fields method, reasonable simplifications and assumptions on the grounding grid, according to Faraday’s law of electromagnetic induction, I proposed the breakpoint diagnosis method of grounding grid based on magnetic source. And software emulation and simulation experiment tested the feasibility of diagnostic method.This paper mainly includes the following several aspects:① A new breakpoint diagnosis method of grounding grid based on magnetic source is presented. A certain frequency sinusoidal voltage is passed into the ungrounded coil circuit (magnetic source transmitting coil), then the coil can stimulate an electromagnetic field (the primary field) to the ground. According to the primary field, grounding grid webs circuit will produce an alternating current by induction, then this current can generate an induction field (secondary field). So I can infer the corresponding grounding grid conductors if there is a breakpoint in accordance with the second field effect on a field situation.② A single-coil model of breakpoint diagnosis method of grounding grid based on magnetic source is presented. The grounding grid is reduced to a squared grid, and single-coil magnetic source emitting coil is instead of a single hit square coil. The transmit coil is moved on the grounding grid, and the location of the breakpoint is inferred according to the current size of the transmit coil above the grounding grid. Self and mutual inductances between the transmit coil and the ground webs are calculated, then I simplified the diagnostic model. Finally, the single-coil magnetic source model is pptimized.③ For the diagnostic sensitivity of single-coil magnetic source model is not high, the cancellation magnetic coil model structure is proposed. In order to improve the diagnostic sensitivity, the location of the breakpoint is inferred by the size of the magnetic field strength of the receiving coil. Then the feasibility of the diagnostic method is verified by simulation and experimental two ways. Last, the cancellation magnetic source model is optimized.④ The comparative analysis of the advantages and disadvantages of single-coil magnetic source and the cancellation magnetic structure is made. By comparison the single-coil magnetic source is simple and relatively easy to design, but the diagnostic sensitivity is not high. The diagnostic sensitivity of the cancellation magnetic source is high, but the structure of this model is complex and difficult to design. In practical applications, the appropriate structure of the magnetic source model is chosen lepending on the specific requirements.