Fayit Analysis And Calcuiation Of Asymmetric Operation Based On Network Parameter Equivalence Theoty

The power system will occur in a variety of different types of faults,Analysis of faults for the planning and design of power system and fault analysis of power system fault,the setting operation of the power system has a very important guiding role,so people on the power system fault analysis method never stops.China's power generation and electricity distribution center center is unreasonable,the basic national conditions based on the HV and UHV transmission has been put on the agenda.For economic and convenience considerations,HV and UHV transmission lines are generally not asymmetric transposition,which resulted in three phase transmission line parameters.This paper introduces a method of calculating the fault of three-phase parameter asymmetry based on the network equivalent theory by using the symmetrical component method.In this paper,the three-phase impedance is expressed as the three-phase current The decoupling of the three phase impedance of the transmission line is realized.Using the network equivalence theory,the three-phase parameter asymmetric lines are equivalent to the three-phase parametric symmetrical lines with some type of disconnection fault.When there is fault in the asymmetric line of the three-phase parameter,which can be regarded as a complex fault of the three-phase parameter symmetrical lines after the equivalent transformation.For the calculation of complex faults,this paper uses the symmetric component method combined with the network theory to analyze and calculate.The network theory is to think of each fault point as a faulty port.According to the fault port,the three-order network diagram is drawn and the three-order node admittance matrix is written.The three-order impedance matrix is obtained.The three-order voltage equation and the fault boundary condition equation are written,and the voltage and current can be obtained by solving the three-order voltage equation and the fault boundary condition equation.The three-phase impedance is the expression of the three-phase current.When the three-phase current flowing through the transmission line changes,the equivalent three-phase impedance will change.For the calculation of the initial impedance of the transmission line,it is assumed that the initial current flowing through the transmission line is three symmetrical.You can get the initial fault voltage and current using the initial transmission line three-phase impedance to do fault calculation.The initial fault current flowing through the transmission line is replaced by the three-impedance formula of the transmission line,and the three-phase impedance of the new transmission line can be obtained.The new three-phase impedance of the transmission line can obtain the positive and negative zero-sequence admittance of the new transmission line,so that a new three-order node admittance matrix can be obtained,and a new three-order impedance matrix is obtained.The new three-order voltage equation and the fault boundary condition equation are written to solve the new fault voltage and current.It has been iterated until the percentage of error before and after the calculation of the fault current value reaches a given convergence accuracy.At this point,the resulting voltage and current is the transmission line three-phase parameter asymmetry fault occurs when the fault voltage and current.The algorithm is programmed by matlab programming,and the system model is simulated by EMTP.The correctness of the algorithm is verified by comparing the two.