Chave controlada para redução de sobretensões de manobra em linhas de transmissão.

Abstract

This work presents a control device implemented in a DSP (Digital Signal Processor) to estimate suitable times for closing and reclosing circuit breaker contacts during three-pole transmission line switching, taking into account trapped charges and line compensation effects. The controlled switching method implemented in the DSP is based on a simple zero crossing algorithm. In order to minimize the effect of the electromagnetic coupling between transmission line phases, the time span between the closing instant of the first and the last pole is as small as possible. The controlled switch is tested in a Real Time Digital Simulator (RTDS™) where was modeled the power system, that consists in a source, a fictitious transmission line (voltage class 550 kV and 400 km long) with real parameters of part of the network of Companhia Hidro Elétrica do São Francisco (CHESF), two equivalent sources and circuit breakers. In the simulation, the controlled switch (DSP) receives a command signal from the RTDS™ to close the circuit breaker, delays this command signal in a time interval such that the making instant of the breaker contacts is near the zero crossing voltage, and sends back the delay trip to the RTDS™ and the breaker is closed in a making instant. The statistical dispersion in the circuit breaker operation time is considered. The presented results are fairly good attesting the efficiency of the method to reduce switching overvoltages.