Detection And Analysis Of Initial Faults In Capacitor Banks

As an important reactive power compensation equipment,shunt capacitor banks are widely used in power system.With the expansion of the scale of power system and the increasement of people’s demand for electric power,the relationship between the safe and stable operation of power grid and the operation of capacitor banks is getting much closer.Faults of capacitors or capacitor banks may lead to inadequate reactive power in power grid,resulting in voltage drop and increase of active power loss,and even large-scale blackouts.which makes it more important to ensure the normal operation of capacitors and capacitor banks.Due to the particularity of capacitor structure and frequent input and output,the failure rate of capacitor banks is pretty high,and the fluctuation of voltage and current caused by the initial failure of capacitor banks is generally small,so the corresponding protection allocated is normally not sensitive enough to react,which also cause the deterioration of capacitor bank fault.Component breakdown fault is the most common fault among the initial faults of capacitor banks.At present,the research on the faults of capacitors and capacitor banks mainly focuses on the physical characteristics of capacitors themselves,including the materials of capacitors,insulating media,internal temperature of capacitors,etc.Some of the researches are based on the electrical quantity of capacitors,but more of them are based on the steady-state process.In this paper,aiming at the most common aging breakdown faults of internal components and input breakdown faults of components in capacitor banks,the characteristics of transient current after fusing of component breakdown are deduced and calculated.According to the structure of capacitor bank,the fault circuit is simplified to the fault equivalent circuit.Conbining with the circuit principle,the differential equation and state equation of fault circuit are listed.The breakdown fault characteristic information of capacitor bank is established on the basis of the time constant of transient current attenuation and oscillation frequency.Then,two methods of transient extract,the wavelet transform and TLS-ESPRIT(Total Least Squares-Rotating Vector Invariant Technology),are introduced.The theoretical characteristic analysis is validated on Simulink of MATLAB.Transient signals of breakdown fault of capacitor banks are measured in theoretical system,IEEE 13-bus system and 34-bus system respectively.Through wavelet transform,the breakdown fault signals of capacitor banks are measured.With TLS-ESPRIT technology,the breakdown characteristic information of the fault signal is obtained.Both of them are consistent with the theoretical calculation value,and the correctness of the theoretical analysis is proved.Finally,the development status of breakdown fault of capacitor components is evaluated by summarizing research and theoretical analysis,which provides a valuable idea for the health status evaluation of capacitors under the influence of damaged components.In summary,through theoretical analysis and simulation verification,through the proposed method for assessing the breakdown fault characteristics of capacitor banks and the health status of capacitors under the influence of damaged components,the research on transient changes and fault development during the breakdown process of capacitor banks has been improved.The data acquisition of this method is simple and direct,with good anti-interference ability.It provides a new solution for the initial fault detection and analysis of capacitor banks.