Research Of Fault Line Selection With Transient Components Based On The Intrinsic Mode Energy

In our country, arc-suppression coil is widely used in neutral point grounding in mediumvoltage distribution network. When the single-phase-to-ground fault has occurred, the faultcurrent is weak because of the compensation effect of arc suppression coil, meanwhile, the arcis unstable and fault conditions is so complicated that the fault line selection hasn’t beensolved well in resonant grounded system. The main problem of using fault steady-statecomponents to fault detection is that the steady-state components are too small to detect.Compared with the fault steady-state components, the fault transient components have someadvantages, such as large amplitude, non-influenced by arc suppression coil and highsensitivity, etc. Therefore, the characteristics of transient process are studied for the sake ofexploring new method of fault line selection.In view of the single-phase-to-ground fault transient process characteristics mechanismin resonant grounded system are unclear, considering the grounding resistance, thecharacteristics of single-phase-to-ground fault are analyzed. The functions between thetransient current and fault time as well as grounding resistance are analyzed according todynamic circuit, so as to reveal the single-phase-to-ground fault transient processcharacteristics mechanism in resonant grounded system fundamentally.On the basis the analysis of the transient characteristics, from the view of energy, theempirical mode decomposition is combined with energy, and the intrinsic mode energy,energy weight coefficients and relative energy factors are defined as fault characteristicparameters, so as to pick fault transient information. The fault line selection method based onintrinsic mode energy is proposed, the intrinsic mode energy of zero sequence transientcurrent of each line are fetched after the fault has occurred, the energy weight coefficients andrelative energy factors of each line are calculated, the relative energy factors of each line arecompared to realize fault line selection. After simulating by changing compensation degree ofarc-suppression coil, mixing the zero-sequence current with noise, injecting harmonics component into system, and changing the line structure, the proposed fault line selectionmethod has been verified reliable for single-phase-to-ground fault in resonant groundingsystem.Three kinds of resonant grounding system model (overhead lines, cable lines, hybridtransmission lines) are established, the new method is analyzed and verified under differentfault conditions. Besides, its performance has been proved according to the recorded datafrom10kV high voltage physical experimental system. The study has shown that the fault lineselection method based on the intrinsic mode energy can achieve fault line selection inresonant grounding system accurately and reliably.