The Method And Application Of Electric Braking Of Hydro-generator With Consideration Of Protection And Security Control

When the hydro-generator uses mechanical brake only, it uses brake hoop andbrake block to slow down the rotate speed to zero by friction. During the brakingprocess, brake block may be frayed and releases a lot of dust by friction. Especially forthe hydro-generator with frequent start-stop, if the temperature rises too high duringbraking process, the brake loop may be out of shape because of the heat, and the wearpattern of brake block and brake loop is also more serious. So it is necessary to researchon the electric braking method of hydro-generator.This paper firstly comprehensively analyzes the electric braking from two aspectsof method of electric braking and control of electric braking torque. According to thecharacteristic of these three different methods of electric braking, the application ofdifferent electric braking methods is summarized;the electric braking torque is analyzedand derived, and the control scheme of electric braking torque is divided into twophases, then the characteristic curve of braking current and braking torque is drawn withthe parameter of rotate speed.According to the need of research, the influence on relay protection and electriclocking caused by electric braking is analyzed. The related relay protections influencedby electric braking in hydropower station contains stator ground fault protection,differential protection, negative current protection, inadvertent energizing protectionand relay protection of generator-transformer expanding unit. The risk of electriclocking control is also studied and the solutions are proposed.Combining the theoretical research and engineering needs of the braking systemmodification of Second Power Dam of Tiansheng bridge, this paper expounds theconcrete implementation of modification scheme of electric braking in detail. From theaspects of modification necessity, technical feasibility, design scheme selection and themain equipment selection, the concrete implementation is researched in detail;considering the effect of electric braking to relay protections and electric locking control,the measures to reduce the influence to relay protection is proposed with the consideringof the reality situation of this hydropower station. Then the risk of control system ofelectric braking is evaluated and the automatic control strategy and principle ofinterlocking logic based on safety guide is put forward.The achievement of this paper can provide reference to the design and modification of braking system of large capacity hydro-generator in the future.