Internal sudden short‐circuit response of a new HSBDS for brushless synchronous machines tested on a 15 MVA generator

Abstract

Synchronous generators with brushless excitation have the disadvantage that the field winding is not accessible for the de-excitation of the generator. This means that, despite the proper operation of the protection system, the large de-excitation time constant may produce severe damage in the event of an internal short circuit. This paper describes a novel high speed de-excitation system (HSBDS) aimed at limiting the damage in the synchronous generator in case of an internal short circuit. The HSBDS for these generators was developed and it is in commercial operation. However in a power plant is not possible to test the operation of the HSBDS under sudden short circuit. This paper presents the results of a several tests in a laboratory 15 MVA brushless synchronous machine where internally reduced voltage sudden short-circuits have been performed. As a rated voltage short circuit could damage the laboratory 15 MVA machine, a computer model has been developed in order to assess the performance of the HSBDS in a real short circuit at rated voltage. The HSBDS under sudden short circuit conditions has been evaluated and validated through laboratory tests and computer simulations with satisfactory results.