Neutral Point Ungrounded System Research Articles

Analysis of A Few Continuous Ferromagnetic Resonance PT Faults in Power Plants and Improvement Measures of Harmonic-free Suppression Technology

Many vicious faults of burning PT and high-voltage fuse caused by ferroresonance occurred in power plants. Microcomputer harmonic elimination device and silicon carbide harmonic elimination device did not work; particularly silicon carbide harmonic elimination devices burnt together with PT. This paper, enumerating the excitation conditions of PT ferromagnetic resonance, analyzes the circuit characteristics of PT circuit ferromagnetic resonance in the power plant and the power frequency voltage characteristics of the sound phase when the single-phase grounding fault occurs in the neutral point ungrounded system. The defects of the existing harmonic elimination device are summarized, and the technical improvement measures are proposed to add the current-sensitive intelligent harmonic elimination device. Practice shows that this kind of harmonic elimination device can effectively avoid PT bursts and fuse-fusing faults caused by the resonance of the intermittent grounding of the system.

Application of 66kV Active Intervention Grounding Arc Suppression Device

The energy supply is mainly based on electric energy at present, and power supply reliability is an important indicator for evaluating power supply services. In view of the 66kV transmission voltage level unique to Northeast my country, the neutral point of the transmission system directly affects the stable operation of the power system. First, the composition of the substation in the system and the working principle of the arc suppression device are analyzed. Secondly, when a single-phase grounding fault occurs in a 66kV neutral point ungrounded system, an active intervention grounding arc suppression device is designed. Finally, the operating characteristics of the designed grounding arc suppression device are demonstrated based on the simulation results.

Single-Phase-to-Ground Fault Location Method Based on SOGI

Most fault location methods depend on the exact extraction of fault transient feature. However, due to the weak grounding current, arc grounding and intermittent problems, it is difficult to extract the fault transient feature. Based on second-order generalized integrator (SOGI), a single-phase-to-ground fault section location method for neutral point ungrounded system is proposed to address this problem in this paper, which avoids the extraction of fault transient feature. Firstly, the fundamental wave phases of zero sequence voltage and zero sequence current are extracted by second-order generalized integrator. Then, the fault position is located based on their phase difference. Finally, the proposed strategy is tested by the simulation data and the field data. The test results show that the method proposed in this paper can accurately locate fault position. Moreover, the phase extraction method based on SOGI is more accurate than traditional Euler method.

Fault Location of Single-Phase-to-Ground in Neutral Point Ungrounded System

Fault Location of Single-Phase-to-Ground in Neutral Point Ungrounded System

A Novel Fault Section Location Method Based on Energy Spectrum Entropy of EMD and Fuzzy C-Means Algorithm for Small Current to Ground System

A fault location method of small current to ground system is proposed in this essay. First, the IMF component is obtained through the EMD of the transient zero-mode current at each detection device or FTU when fault occurs. Second, the definition of EMD energy spectrum entropy is put forward to measure the distribution of signal energy in the scale domain, based on which the energy spectrum entropy factor value reflecting the highest frequency IMF component is obtained. Third, FCM algorithm is adopted to cluster analyze the first IMF component spectrum entropy factor from the two feature matrixes of local and global variables. Finally, the fault section is accurately judged through the evaluation of the fuzzy membership degree matrix. In addition, the analysis of global variable clustering center matrix can show the slight differences between the IMF1 power spectrum entropy factor value of health section and that of fault section. A good many simulation calculations show that, this method can accurately and reliably judge fault sections at any time under any grounding resistance value whether it is in the neutral point ungrounded system or arc suppression coil grounded system.

Research on Capacitance Current Treatment Methods in Mine High-Voltage Power Grid

In view of the coal mine neutral point ungrounded system when single-phase ground fault occurs, the grounding capacitance current is too big affect the security of coal mine powe supply.The paper analyzed testing data of capacitance current of coal mine network, established a treating scheme of capacitance current according to evaluating results, namely automatic tracking compensation arc suppression coil devices. The running results show that the scheme limits the size of the ground current and decreases rate of accidents of arc grounding over-voltage, which is good for improving the power supply safety.