Estudo da polarização elétrica residual nos resistores não lineares à base de óxido de zinco.

Abstract

In this work the phenomenon of residual electrical polarization in non-linear resistors based on zinc oxide when stressed with current impulses was studied, and how this polarization affects the protection level of the ZnO surge arrester. The ZnO surge arrester consists of non-linear zinc oxide-based resistors mounted in series or in series-parallel combination. For the study of this phenomenon, it was initially carried out tests of tangent of losses, capacitance and partial discharges in all non-linear resistors based on zinc oxide. These tests had the objective to select the nonlinear resistors based on ZnO with the quality standard necessary for the good performance of this work. The study of the polarization of the nonlinear resistors based on zinc oxide was analyzed when submitted to current pulses, with wave form 8 / 20us (European standardization). Current pulses were obtained through a HAEFELY pulse generator type 221-100 KV, 100 KA. During the work, the non-linear zinc oxide-based resistors (33 samples), international standard, were submitted to the analyzes listed below: 1. Verification of the polarization effect as time (07 samples); 2. Verification of the polarization / depolarization temperature effect (14 samples); 3. Verification of the polarization effect over time, with the voltage applied continuously, and with the temperature (02 samples); 4. Verification of the effect of polarization on the residual voltage in non-linear ZnO-based resistors (10 samples). The results obtained during the whole experimental procedure prove the existence of residual electrical polarization in non-linear resistors based on zinc oxide stressed with current impulses, as well as their decrease over time and with the voltage continuously applied. The resusltados also show the polarization behavior with the temperature and the influence on the protection level of the ZnO surge arrester.