Research On Parameter Calculation Of UHC/EHV Transmission Lines

The transmission line parameters are the basic data of relay protection setting,state estimation,power flow and transient stability calculation and fault location.The accuracy determines the reliability of the calculation results.The traditional method is to measure the line parameters before the line is put into operation.The line parameters will change due to factors such as season,temperature,humidity and line aging after the line is put into operation.In order to obtain the parameters during line operation,the parameter calculation method based on PMU and SCADA system is proposed,But due to PMU cost is high,the PMU application is very limited.This paper proposes a time domain calculation method for transmission line parameters using single-phase reclosing and fault recording data before and after non-full-phase operation.Firstly,a line parameter calculation method using fault recording data during non-full phase operation is proposed.For the non-faulty line,the positive sequence and zero sequence parameters are selected by the line mode ? type or T type centralized parameter model,and the zero mode ? type or T type centralized parameter model calculation.Positive sequence parameter selects the non-fault phase phase-to-phase line mode ?-type or T-type centralized parameter model calculation.If the secondary arc is not extinguished,the three-phase coupled line model is selected to calculate the zero-sequence parameter of the faulty line.If the secondary arc is extinguished,the zero-mode ?-type or T-type centralized parameter model is selected to calculate the zero-sequence parameter of the faulty line.Secondly,the sensitivity of each parameter of the ?-type and T-type lumped parameter models of the transmission line is calculated by the definition of parameter sensitivity.The sensitivity of the line parameters to voltage and current in above two models is obtained respectively.The model error,CT and PT error and time are taken into consideration.Influencing factors is analyzed,such as synchronization error,the error of line parameter calculation.Finally,the parameters calculation of shunt reactor transmission line and three-phase unbalanced transmission line are studied.For transmission lines with shunt reactors,the selection of T-type lumped parameter models is used to establish equations and solve the line parameters.For the three-phase unbalanced transmission line,the three-phase asymmetric ?model is selected to calculate the three-phase coupling capacitance and the capacitance to the ground.This paper first uses the low-pass filter to filter the current and voltage in order to reduce the influence of model error.Further,the least squares algorithm is used to solve the equation to obtain the line parameters.The simulation results of ATP-EMTP show that the error of the line parameters obtained by the proposed method is small and can meet the engineering needs.