The Research And Design For Turn-to-Turn Insulation Monitoring Device Of Rotor Windings In Generator

With the increasing capacity of steam turbine generator, The safe and stable operation of large steam turbine-generator unit is essential for the power system. In order to monitor the insulation state of rotor winding, this paper study a On-line device for monitoring the insulation state of rotor winding in generation. It can find the warning signs of fault timely in fault budding period, and provides reference for reasonable arrangements of maintenance to improve the safety and the economy of plant operation.This paper analyzes the air gap magnetic change of rotor winding inter-turn when it is short circuit, all sorts of reasons and mechanism of shaft voltage,and it focus on the relationships of static excitation shaft voltage, common-mode volatage and DC excitation voltage, the common detecting methods of shaft voltage. Simulation models of generator shaft and excitation system are established in Matlab/Simulink using power system toolbox. Based on the spectrum analysis of the low frequency and high frequency shaft voltage, it proves that shaft voltage generated by static excitation consists mainly of odd harmonics; through the analysis of the data collected in plant it shows that it will produce additional even-order harmonic component of the shaft voltage after the turn-to-turn short circuit. This paper introduces the double-end RC sampling circuit of shaft voltage, front analog amplifying circuit and a series of signal processing circuit. It makes a front-end amplifying circuit,and achieves the requirements of function and characteristics through the test of actual circuit board. It introduces the building and debugging method of hardware platform of PC/104data acquisition system, accessing to the specific methods and steps of installation and debugging by practical exploration. And it put forward to the problems and solutions in debugging. By writing the MFC application program in VC6.0, it achieves the data acquisition and saves into a MySQL database. At last, it analyzes the error and sampling accuracy of the data of sine wave, square wave and triangle wave.