Prediction of long-line radio-interference field from measurements on multiconductor short-line

Abstract

A general method for predicting the long-line radio-noise field from measurements made on short multiconductor test line is presented. The method uses the measured values of the corona current and magnetic field, and the computed transform operators. These operators are obtained by means of an algorithm, based on the lattice technique, which takes account of the radio-frequency corona current propagation on short multiconductor lines having any terminal impedance. The transform operators may be used, even if the actual line and the test line have different geometric configurations. These operators were computed in the past by means of methods based on modal analysis, which may be used only if the terminal impedances of the short test line do not give rise to the intermode coupling: generally, this condition is not satisfied in conducted measurements of corona current. The paper also presents an algorithm for the computation of the radio-interference voltages, which wifi be used in a further study concerning the prediction of the corona noise in power-line carrier channels. The prediction method was applied to the analysis of the radio- noise field generated by the Enel's 1000 kV multiconductor test line at Suvereto, by using experimental data already known. A parameter sensitivity analysis of the transform operators was carried out with the aim of suggesting the optimal procedure for making the experimental tests. The results obtained demonstrated the convenience of using the values of measured corona currents in the transform formulas. To effect the measurements, it is preferable to have configuration with nonenergised conductors earthed at the supply end and all three conductors open at the other extremity