The Simulation Research On 10kV Potential Transformer Fuse Breaking And Inhibition Measures

In the neutral ungrounded distribution network, electromagnetic voltage transformer is usually mounted on the generator or substation bus to monitor ground voltage, in order to use the instrument measure ground voltage directly. Voltage transformer usually uses Yo/Yo/A connection and the primary winding neutral grounding.After the occurrence of certain operating, fuse breaking problem occurs frequently because of the interaction of the nonlinear excitation winding and system ground capacitance, causing electromagnetic voltage transformer burned, power outages, seriously affecting the safe operation of the system.The main researches aiming at fuse breaking problem are as follows:Firstly, the research status at home and abroad of the pressure dependent fuse is reviewed. Then the fundamental of ferroresonance and low frequency oscillation caused by PT saturation are introduced. Lastly combined with simplified circuit schematic, the ferroresonance, including type, excitation conditions and the regional scope of the various types of resonance is analysed. Besides, a mathematical analysis of low-frequency oscillations and the low-frequency saturation current is made by using virtual compensation variable method.Electromagnetic voltage transformer model and lOkV neutral ungrounded system mathematical model are established based on ATP-EMTP simulation platform and main electrical wiring diagram and parameters of lOkV distribution network for a substation. After the disappearance of single-phase ground fault, ferroresonance is simulated and analyzed, studying the impact of the ground disappearing moment. Then low frequency oscillation is simulated and analyzed, studying the impact of ground capacitance size and single phase ground disappearing moment.Simulate and discuss the inhibitory effect of several common elimination measures to transformer fuse blown, summarizing the advantages and disadvantages of each method. Then combined with lOkV distribution network of a substation, the problems after connecting a nonlinear resistance eliminator between the neutral point and high voltage side of PT and ground are analyzed, and a new improvement is proposed based on these questions.