Some Aspects of Sustainable Energy Conversion During Transient Processes in Electric Power Systems Comprising Generator Circuit Breakers

Cornelia Bulucea,Doru Nicola,Nikos Mastorakis,Carmen Bulucea,Marc Rosen

doi:10.3390/wsf3-d001

Abstract

This paper is a sequel to a study by the authors of the electric power systems comprising the generator circuit-breakers (GCBs) at power plant generator terminals. A sustainable assessment of the current interruption requirements of a GCB addresses the main stresses on the generator circuit breaker, revealing that the GCB current interruption requirements are significantly higher than for the distribution network circuit breakers. Hence, generator circuit-breakers are subject to unique demanding conditions caused my specific stresses, namely: high asymmetrical fault currents resulting from high d.c. components of the fault current; greater electrical, thermal and mechanical stresses when interrupting longer arcing time faults; and important dielectric stress after the electric arc extinction caused by the transient recovery voltage (TRV). This paper extends other studies of the authors of the energetic and exergetic transformation chain at the interruption current transient process in an electric power system that comprises the generator circuit-breaker, as well as the transient recovery voltage (TRV) which appears after the interruption of a short-circuit fed by the synchronous generator or by the main step-up transformer. For achieving the TRV equivalent configuration the authors applied the method of operational symmetrical components (o.s.c.), and utilized the operational impedances of synchronous generator and of main transformer, depending on the fault location. Modeling the transient recovery voltage of circuits emphasizes aspects with direct implications on commutation equipment. Thus, the o.s.c. method can be applied at the poles of any breaker, for any eliminated fault type, if the network configuration and elements are known. The TRV, which appears after the interruption of a short-circuit fed by the generator, may be considered like an oscillation, where the oscillation factor and the rising rate (RR) of the TRV are established by the electrical machine parameters: resistance, inductance and capacitance. Consequently, modeling of concentrated equivalent parameters of the synchronous generator at perturbations caused by current interruption transient processes is achieved in this study through an approach based on sustainability concepts. These findings allow for simulations of the transient recovery voltage and comparisons with experimental results.

Highlights

In previous studies [16,17,18,19] we have shown the configuration of the key fault current encountered by the generator circuit breaker, namely: generator-fed faults; transformer-fed faults; and generator-fed faults, on the high voltage side of the main step-up transformer
To interrupt these kinds of faults, generator circuit-breakers are subjected to specific stresses: 3 - The GCBs must be capable of interrupting the high symmetrical fault current, and the higher asymmetrical faults currents resulting from high d.c. components of the fault current [5,6,7,8,9,10]
This paper extends other studies of the authors which have examined the exergetic transformation chain at the interruption current transient process in an electric power system that comprises the generator circuit-breaker

Summary

Introduction

Following the notion that life on Earth demonstrates sustainable energy conversion [1,2,3,4], we aim to highlight that an approach to an electrical power system according to the patterns defined within the sustainability framework could provide a synoptic view of electromagnetic interaction phenomena within an electric power network entailing a generator circuit-breaker (GCB) at the terminals of the synchronous generator of an electric power station [5,6,7].The electric connection circuits of power stations encompass GCBs at the generator terminals, since the presence of that electric equipment is related to the sustainability of a power plant [4,5,6,7,8,9,10,11,12,13,14,15]. In previous studies [16,17,18,19] we have shown the configuration of the key fault current encountered by the generator circuit breaker, namely: generator-fed faults (which can be insulated or grounded threephase and two-phases short-circuits); transformer-fed faults (which can be insulated or grounded threephase and two-phases short-circuits); and generator-fed faults, on the high voltage side of the main step-up transformer (which can be insulated or grounded three-phase and two-phases short-circuits, as well as single-phase short-circuits) To interrupt these kinds of faults, generator circuit-breakers are subjected to specific stresses:.

Objectives

Methods

Conclusion