Research And Suppression Of Oscillation Mechanism Of Distribution Network

The operation and maintenance of the power system is inseparable from the participation of the voltage transformer(PT).As the power system becomes more and more complicated,the requirements for parameter detection and equipment protection are more stringent.Specifically,the PT can provide energy for relay protection devices and measuring instruments,and can provide protection for transformers and motors in the event of line faults,and can be used to detect power,voltage and other parameters,thereby achieving normal operation and maintenance of the power system.Once the voltage transformer is damaged,it will affect the operation of the power grid from various aspects and to varying degrees,and eventually affect the end of the power supply such as residential life and oil field production.Oscillation of oilfield distribution network is the main reason for inducing damage to voltage transformers.It is necessary to clarify the oscillation mechanism of oilfield distribution network,and then develop targeted improvement measures,which can effectively overcome the problem of frequent damage of PT.Compared with the traditional linear circuit,many nonlinear components,such as PT,transformer,etc.,are installed in the distribution network.The external disturbance can cause the steady-state resonance of the distribution network,and the overvoltage that causes serious damage to the voltage transformer will be triggered.Current,this phenomenon is called"ferromagnetic resonance."Firstly,the substation with PT damage failure is selected for investigation,and relevant parameters,wiring and other information are obtained.Based on this,a simulation model is constructed,and a typical scenario of recurring resonance phenomenon is simulated based on this model.The Shengli oilfield distribution network was selected as a typical object.The PT burnout fault was reproduced on the basis of parameter sorting and simulation model,and the basic conclusion was drawn that the small disturbance could stimulate the distribution network to generate overcurrent and overvoltage.When the voltage transformer is operated for a long period of time,damage may occur,and the relationship between the disturbance and the overcurrent overvoltage strength and duration is complicated.The three modulus network models of the distribution network are constructed by phase-to-analog transformation.Based on the model,several typical resonance phenomena are analyzed,and the PT burnout failure mechanism of the neutral point ungrounded distribution network is proved,and the conclusion is drawn:The fault-excited grid disturbance can cause near-steady-state "transient resonance".The operating state of the system and the excitation characteristics of the nonlinear ferromagnetic winding jointly determine the frequency and amplitude of the transient resonance;the grid disturbance caused by the persistent fault is caused by The important causes of steady-state resonance,in addition to the stability margin of the non-resonant operating point,the initial state of the system,etc.,and the quantitative relationship between the amplitude and the system state parameters.In this paper,the PT excitation characteristics are studied.The preconditions for the PT transient resonance and steady state resonance are determined according to the equal area rule.The deep relationship between the system equilibrium point and the disturbance is clarified,that is,the transient resonance around the equilibrium point and the steady state resonance Work at an abnormal balance point.Therefore,eliminating the steady-state equilibrium point of the power system can effectively avoid the ferromagnetic resonance phenomenon,and then fundamentally solve the PT burn-out failure.Following this line of thinking,this paper proposes a package of anti-vibration measures,and has achieved beneficial results overall.