Study On Rotor One Point Ground Fault Protection For Brushless Synchronous Generator

Modern power industry mostly uses synchronous generator to generate electricity. Synchronous generator is in a most prominent position in the power system, its operation reliability directly affects the stable run of the power station and guarantees to use electricity safely and economically. Due to a certain limit of the installation and the structure, the rotor could be severely affected by the centrifugal force when the generator is rotating at a high speed. So the probability of occurring rotor insulation fault is very large.Rotor ground fault is one of the common faults to generator. When rotor one point ground fault of synchronous generator occurred, it couldn’t bring a direct threat to the generator, so the generator can continue operate. But when two points ground fault happens, the safety of the generator and the system will be threatened. So the rotor one point ground fault protection device must be installed for the safety of generator to avoid two points ground fault. So far. rotor ground fault protection for synchronous generator mainly aims at synchronous generator with brush, but the theories of rotor one point ground fault protection for brushless synchronous generator are far from perfect.This paper firstly introduces the existent methods of rotor one point ground fault protection for synchronous generator with brush. Secondly it analyzes the special structure and working principle of blushless synchronous generator. Then two novel schemes of rotor one point ground fault protection for brushless synchronous generator were put forward. The schemes are as follows:(1) Keeping the terminal lead of the rotor unchanged, the paper proposes three principles of one end voltage injection type for rotor ground fault protection. One is protection with injection square wave voltage to the negative end, another is protection with injection DC voltage to the negative end, and another is protection combining the principle of voltage injection type with ping-pong type.(2) Changing the terminal lead of the rotor by brush lifting device, the paper proposes two principles of two ends voltage injection type for rotor ground fault protection. One is ping-pong type protection with injection DC voltage to the two ends and the other is protection with injection square wave voltage to the two ends. This paper analyzes the new principles of rotor one point ground protection and builds rotor ground fault simulation models based on Matlab/Simulink software. What the emulation experiment manifest is that the schemes can satisfy the needs of preciseness and delicacy for brushless synchronous generatoor.What has been studied in this paper provides a certain theoretical reference for the actual rotor one point ground fault protection for brushless synchronous generator.