Study on online calculation method of transmission line parameters

Transmission line parameter is important for obtaining power network structure, generating power system node admittance matrix or impedance matrix to calculate power flow, calculating short-circuit current, and setting relaying protection devices. But actually, transmission line parameters applied in power system are mostly experience values or offline measuring values provided by manufacturers, they may quite different from real parameters. This will influence the precision of power system analysis and calculation. This paper studies online calculation methods of transmission line parameters based on phasor and sampling value, it can calculate positive sequence parameters and also negative sequence, zero sequence parameters to improve the accuracy of fault analysis and relay protection settings. Different types of transmission line models are built by PSCAD to test and verify the calculation methods, results show that the proposed methods for transmission line parameters online calculation have high accuracy and reliability, they can provide reliable basis for power flow calculation, protection setting, operation reliability and safety of power grid.