Análise de uma nova proposta para identificação de faltas de alta impedância em redes aéreas de distribuição

Abstract

High impedance fault detection (FAIs) has been a formidable challenge for power distribution systems. In general, FAIs are associated with the primary conductors of the distribution network when exposed to objects such as trees, buildings or even the ground in the event of a conductor rupture. This type of fault does not, in fact, produce sufficiently high currents for the correct detection of overcurrent in protective equipment, such as fuse breakage, automatic closing of reclosers and disconnectors. In these situations, where the occurrences of FAIs are directly associated with the breakdown of live conductors, the resulting high fault impedance current is not high enough and the overcurrent equipment upstream will not detect over there. Consequently, the conductor will remain energized on the ground with voltages from a few hundred to several tens of thousands of volts, endangering the lives of people and animals. Since the 1970s, several studies have been conducted to find a suitable technology for detecting FAIs. In these studies, each with a different approach to the problem, the most varied of techniques were used, however, these techniques did not present high reliability and safety in terms of detection and differentiation between an occurrence of an FAI and events common to distribution lines as load shifting or capacitor bank switching. Thus, the present work brings a new proposal using the characteristic of the interharmonic signature present in the current signal of this type of fault. To verify the efficiency of the proposal, a prototype of a recloser with an intelligence developed to detect these signatures was built and several tests on different types of soils were carried out within a field test built specifically for this purpose. The results showed that the proposed technique is very promising.