Research On The Fusing Of Voltage Transformers’ High Voltage Fuse

According to the survey,the problem of high voltage transformer’(PT)high-voltage insurance meltdown is common in China’s medium-voltage distribution network,and it threatens the stability of grid operation and the level of electricity supply and consumption of users,which is a concern for people.A platform in the offshore oilfield power grid frequently has PT high voltage insurance meltdown accidents after single machine operation,so far the cause of the accident has not been identified,seriously threatening the safety and stability of the oilfield power grid and normal production.Therefore,it is of great significance to study the causes and suppression measures of frequent or abnormal PT high-voltage fuses to help solve practical engineering problems and ensure the stable and normal operation of the power grid.First,through extensive literature review,the most common causes of PT high-voltage fuse melting are ferromagnetic resonance,low-frequency nonlinear oscillation and the influence of the fuse’s own fusing characteristics.Then,combined with the nonlinear excitation characteristics of PT,a detailed theoretical analysis of the mechanism and classification of ferromagnetic resonance,the mechanism of low-frequency nonlinear oscillation,and the influencing factors of the fusing characteristics of the fuse was carried out to explore the principle of the PT high-voltage fuse fusing problem.Then,the article launched a simulation study based on electromagnetic simulation software ATP-EMTP.First,the simulation model of 10 k V neutral ungrounded system is built,and the waveform diagrams of high-frequency resonance,fundamental-frequency resonance,split-frequency resonance and low-frequency nonlinear oscillation are obtained by changing the parameters of capacitance to ground,and the waveform characteristics of each resonance are summarized.Because of the widespread use of urban construction and cable lines,the chances of fractional-frequency resonance and low-frequency nonlinear oscillation are the largest in the present distribution network.So the effects of PT excitation characteristics,system zero-sequence damping,single-phase grounding transition resistance and intermittent transient single-phase grounding on both are investigated for these two resonances.Finally,a simulation analysis was conducted for the platform where frequent PT highvoltage fuse meltdowns occurred in the offshore oilfield grid.Then,based on the characteristics of the resonant waveforms analyzed in the previous section,it was determined that the low-frequency nonlinear oscillation was the cause of the PT highvoltage fuse meltdown,and the inrush current amplitude exceeded the fusing current of the fuse itself.At the same time,the original detuning measures of the platform were simulated and proved that they could not reduce the amplitude of the low-frequency inrush current.Finally,combining with the actual situation of the platform power grid,we proposed to replace the high-voltage fuse with higher fusing current or install a harmonic eliminator at the primary neutral point of PT,and proved the feasibility of the scheme through theoretical analysis and simulation.