Desarrollo e implementación de un sistema para la medición de los parámetros eléctricos de líneas de alta tensión en presencia de interferencias debidas al ambiente eléctrico real

DR. HUMBERTO ZINI; ING. JUAN M. SERRANO MORA; ING. LEOPODO RODRIGUEZ; ING. GUSTAVO BARON

Mar del Plata

Congreso; CLAGTEE 2017 ? XII Latin American Congress on Generation, Transmission and Distribution; 2017

Accuracy of line parameters (i.e. longitudinal impedances and cross admittances per unit length) is of primary importance for setting line protection relays and for a correct line modeling in system studies. Inadequate accuracy could even lead to system instability, with serious technical and economic concerns.In Argentina assessment of line parameters by measurements is usual part of the commissioning tests of HV and EHV overhead lines.Line parameters are calculated from a set of electric magnitudes (e.g. loop impedances, admittances and losses) which are measured in proper tests made at one line end with the other one open and short circuited. In both the measuring and calculation steps, the procedure raises some difficulties that motivate the development here presented. An important issue is the electric and magnetic coupling with in service overhead lines or other near apparatus, which induce power frequency voltages and currents. These interferences can seriously affect the measurement of impedances and admittances when the power source used in the tests is also of the network frequency. For some years now, there are on the market test equipments that avoid this error by estimating the impedances at power frequency from a set of measurements performed at frequencies near to but different from the problematic one. They rely on power electronics to generate the test voltages of different frequencies and on digital processing to filter the power frequency interferences from the digitized voltages and currents. The Instituto de Energía Eléctrica of the National University of San Juan, Argentina, has undertaken a development based on this approach. The main concepts, oriented to reduce the power of the test source, as well as the first results, are shown in the paper.The paper also addresses the procedure to calculate the parameters of the line from the measured magnitudes. No well-established procedure exists at present for this task. The methodology usually applied is based on simplifying assumptions that, as will be shown result in significant errors, especially for long lines. An iterative procedure has been developed to avoid this error source. As it will be shown, line parameters are optimized by minimizing the difference between the measured magnitudes and those obtained with a distributed parameter line model with the computed parameters.