Research On Electromagnetic TV Ferroresonance In 66kV GIS System

Recently,there happened several 66 kV GIS ferromagnetic resonance accidents in Liaoning province caused by iron-core saturation of electromagnetic potential transformer.When the fault occurs,the system has a high transient overvoltage,which leads to insulation breakdown and explosion of the equipment,and the failure of the fuse.So it brings great harm and loss to power system.In order to ensure the safe and stable operation of the power grid and transmission equipment,fully astudy the GIS resonance mechanism and find effective protection measures,The study on the problem of GIS resonance overvoltage is especially important.This paper mainly studies the problem of ferroresonance overvoltage in 66 kV GIS system neutral grounded,based on prototype of the accident,study in-depth the mechanism of GIS ferromagnetic resonance,analysis the characteristic of inner GIS electromagnetic TV excitation,explore the motivate condition of systematic iron-core resonance as well as the characteristic of GIS non-linear resonance.By using ATP/EMTP software model to make an equivalent simulation of 66 kV ZF6-72.5C type GIS substation,stimulating multiple stimulates such as single-phase ground connection,close no-load bus-bar,switch line and so on,restoring process of 66 kV GIS ferromagnetic resonance accident.Besides,this paper researches on effects of GIS harmonic suppression methods,verifies effectiveness of those diversity methods through the simulation calculation,thus makes a reasonable solution to control ferromagnetic resonance.The simulation result shows that aiming at the special 66 kV GIS ferromagnetic resonance accidents in northeast China,by changing power exciting TV to a better function,improving saturation resistance of system equipment with iron-core,can kill off resonance production possibility.By switching in zero sequence impedance to TV open-delta winding greatly reduces occurrence probability of GIS resonance.Neutral point virtual connection extinction coil in GIS system effectively destroys original-matched resonance parameter,and have obvious function on resonance elimination.Neutral point series resistance on TV high voltage side prevents from quick saturation state,and prevents resonance phenomena.Emulation calculation and field trial both improved feasibility of those methods.