Identification of double-circuit transmission line parameters in phase coordinates
Initial parameters of high voltage overhead transmission lines can be determined with an error of up to tens of percent. The improvement of parameters and obtaining a mathematical model of an overhead power transmission line suitable to real conditions can be performed on the basis of parametrical identification methods which are carried out based on the measurements of voltages and currents at the beginning and the end of the line. However, the existing methods of line identification are developed for three-wire high voltage lines and cannot be applied to determine parameters of double-circuit transmission lines. A possible approach to the identification of double-circuit line parameters based on measuring voltages and currents of wires at the starting and reception ends is presented in the article. Some parameters of the line are supposed to be obtained by calculation because all parameters of the high voltage line cannot be determined on the basis of measurements. In the algorithm of six-wire line identification the calculation of wire resistance and effective ground conductivity components is made based on the initial mode information, namely, 12 voltage modules and voltage phases and 12 modules and current phases at the line ends. Thus the following data of each wire are considered known: the 1 km line ohmic resistance, each wire radius, wire arrangement coordinates taking into account the sag, the section area, the line length, and an approximate ground conductivity along the line length. At identification it is supposed that the high voltage line has no damages and measurement errors of under-load operation do not exceed 0.5% and 0.5º. The method assumes the correction of voltages and currents at the line reception end and the determination of effective ground conductivity if a zero-sequence current flows. On the basis of computer modeling performed by the Fazonord software package developed in the Irkutsk State Transport University the applicability of the method for determining practical parameters of two-chain lines is shown.