Hardware-in-the-loop simulation and testing of volts per hertz protection scheme for a generator over-excitation system

Abstract

Large generators are essential components in a power plant for ensuring the steady production and delivery of electric power for various purposes; thus, the generator protection system significantly impacts power system stability. Consequently, it has recently become necessary to consider upgrading the existing generator protective devices due to increased power demand and ageing infrastructure. This study proposes an approach for system protection during generator over-excitation condition that occurs when the magnetic core of the generator is saturated. When this occurs, stray flux is induced in non-laminated components, resulting in overheating of the generator. The key aspects considered in this study were the over-excitation circumstances that affect generators and their protection mechanisms. This research work developed a logic diagram for volts per hertz protection relay to prevent over-excitation conditions in a generator. The hardware in the loop test bed is implemented to test the volts per hertz protection schemes. The hardware-in-the-loop (HIL) test-bed was implemented using real-time digital simulator (RTDS) and SEL 700G IED. Simulation results proved that a SEL700G volt per hertz protection function (24) is reliable for overexcited generators.