Research On Ferroresonance Characteristics And Suppression Methods Of CVT

Capacitive voltage transformer(CVT)is an important power equipment in power system,and is widely used in power system of 110k V and above voltage class.CVT contains nonlinear inductance element,which is easy to match with its capacitance to cause ferroresonance under certain external excitation conditions,which will seriously affect the safe and stable operation of the equipment and even make the equipment explode.Therefore,it is of great practical significance for the safe operation of power grid to study the characteristics of ferroresonance of CVT and find a method to suppress ferroresonance.In this paper,the electromagnetic transient simulation software atp-emtp is used to build the CVT full circuit simulation model.Based on this model,the ferroresonance characteristics of CVT are studied.Through the simulation model,this paper makes a series of simulation studies on the influence factors of ferroresonance of CVT.First of all,this paper studies three ways to excite CVT ferroresonance:primary side closing,primary side short circuit and then suddenly eliminate short circuit and secondary side short circuit and then suddenly eliminate short circuit.The simulation results show that the ferroresonance induced by the secondary side short-circuit and the sudden elimination of the short-circuit is the most serious and the over-voltage amplitude is the highest.The ferroresonance excited by primary side closing is the least.Secondly,in the simulation study of the effect of capacitor voltage initial value on ferroresonance of CVT,a short circuit is found at the time when the voltage passes zero and the short circuit is eliminated at the time when the voltage passes zero,capacitor voltage initial value improves the effect of ferroresonance suppression.In other cases,the initial value of capacitor voltage has no effect on the inhibition effect of ferroresonance of CVT.Finally,in the simulation study on the influence of primary voltage on ferroresonance of CVT,it is found that the primary voltage is different,and the severity of ferroresonance of CVT is different.When the primary voltage is 1.0U_N,the oscillation time is the shortest,the overvoltage multiple is the smallest,and the damping effect is the best.At present,the most common way to suppress the ferroresonance of CVT is to parallel the speed saturation reactance damper in the secondary winding of the intermediate transformer and to coordinate with the parallel Zn O arrester at both ends of the compensation reactor.The value of the resistance of the damper plays a crucial role in the damping effect of the damper.The simulation results show that the resistance of the damper has a value range,in which the damping resistance can successfully damp the ferroresonance,and the only optimal damping resistance exists.In this paper,the magnetic density of intermediate transformer core is also studied and it is found that increasing the magnetic density of intermediate transformer is beneficial to suppress ferroresonance.At present,there is no mature theoretical research on electronic dampers.This paper designs an electronic dampers.The simulation results show that the electronic dampers can damp ferroresonance faster than the saturated dampers.In recent years,the failure of abnormal damage of CVT high-voltage side fuse of35k V bus is more and more frequent,which affects the economy of power consumption and stable operation of power grid.This paper USES Matlab to build a simulation model to study the reasons;According to the simulation results,the inrush current of the shunt capacitor gate excites the ferroresonance of the CVT,causing the high-frequency current with a large peak value on the primary side of the CVT to cause the fuse to fuse.Combined with the causes of this failure,the paper finally puts forward several reasonable solutions.There are 7 tables,69 figures and 84 references in this paper.