Research On The Criterion And Device Of Fuzzy Decision-making Fault Line Selection Based On Multi-Source Data Fusion Technology

When the single phase-to-earth fault occurs in the non-effectively grounded system (NUGS), the system can be permitted to operate for a period of time in order to enhance the reliability. However, the over-voltage will accelerate the insulation of equipment to become older, and arose the insulation flashover. Thus, the fault line must be selected and removed quickly and accurately by the fault line selection device. Because of the complexity of NUGS, there are some dead areas for the present fault line selection method, whose adaptability and robust are weak, and the correctness of fault line selection is low. Referring to the characteristics of grounded mode in the NUGS, the criterion of fuzzy decision-making fault line selection is prospered to carry out the fault line selection on the basis of multi-source data fusion, and a fault line selection device is developed and some tests are carried out.Firstly, in this paper the characteristics and application of three kinds of neutral operation mode are summarized. The fault line selection methods and their advantage and disadvantage in the NUGS are detailed. Aiming at the difficult factors of fault line selection, such as the difficult fault modeling, the faint fault signal, the unstable grounding arc and the interfere of arc-suppression or other relay protection, the fault line selection must be carried out by using the multi-source information characters according to the different neutral operation mode.when the single phase-to-earth faults occur, through analyzing the change of phase voltage and fault grounded current, the dividing criterions and characteristics of neutral grounded modes are explained. According to the symmetry weight method, the single phase-to-earth faults of three kinds of grounded modes are analyzed, and the expressions of zero sequence voltage and zero sequence current are detailed, and the distributing laws are indicated under all kinds of grounded modes, consequently, the theory is established for the criterion design of fault line selection in the paper.And then in this paper, the line break of PT'primary winding and the system's phase break and the ferroresonance fault occur in the NUGS, the biggish zero sequence voltage will be exported from the PT's open-delta, whose fault characteristic is similar to the single phase-to-earth fault, which are deeply researched in this paper. At the same time, the criterions of comparing the line voltage to distinguish the line break of PT's primary winding fault and comparing the phase voltage and its change to distinguish the system's phase break are prospered. And the improved interpolate FFT arithmetic and Prony arithmetic are prospered to obtain the harmonic characteristic quickly and accurately when the ferroresonance occurs, and then distinguish the types of harmonic resonance (frequency dividing resonance or higher frequency resonance), so that the ferroresonance eliminator can be effective.Aiming at the low veracity of present fault line selection method, some fault measurement membership functions and some criterion weight coefficient membership functions of fault line selection method are defined inspectively according to the variational law of fault signal character and the intension of fault signal, and the conventional logic judgment is replaced with the fuzzy judgment. Based on the large information fuse technology, the criterion of fuzzy fault line selection for the NUGS is built up under the neutral ungrounded system (NUS) and the neutral resonance system (NES). Especially, some good ways are prospered to enhance the veracity of fault line selection device for the inherent defectiveness of NES, such as increasing the remaining current, cooperating with the arc-suppression coil when carrying out data acquiring and so on. Aiming at many single phase-to-earth fault cases in the NUGS, many simulations are carried out by the EMTP-ATP software, and the fault line selection methods are validated.Finally, according to the criterion of fuzzy decision-making fault line selection built by the theory analysis above, the fault line selection device is developed under the DOS operate system on the basis of the PC104 bus, and some tests are carried out for the fault line selection device. The test results show that the fault line selection device has the high veracity of fault line selection and better application when the single phase-to-earth fault occurs in the NUGS.