Study On Integration System Of Faults Diagnosis And Protection For High-voltage Induction Motors

Induction motors are widely used in industry because of their rigidity, low-cost and high-efficiency. They are the workhouses of any industrial plant and are used for many applications. In some industries the annual failure rate ofmotors is at a considerately high level, the consequent losses and downtime in a factory can be extremely expensive and in most cases, far exceed the cost of the replacement motor itself. Therefore the problem of induction motor protection and faults detection attracted many researchers.This paper defined the idea of motor protection and condition monitoring , described the present state of the motor protection and condition monitoring technique, as well as the trend of the motor protection and condition monitoring technology in China.This paper presents a review of various faults detection methods, theory and put emphasis on the so-called MCSA method (Motor Current Signature Analysis). This technique utilizes the results of spectral analysis of a single phase of the stator line current to monitor the condition of a motor with the advantage of not requiring sensors in addition to those, which already exist in currently available motor protection device. Reliable interpretation of the spectra is difficulty, since the harmonics in question is many times smaller in amplitude than the excitation frequency (i.e., 50Hz). In this paper the frequency domain signature of some motor faults are well identified using the Zoom spectrum analysis and spectrum correction methods, leading to a better interpretation of the motor current spectra.This paper also discussed the problem of three-phase induction-motor overall protection, analyzing the causes and protection principles of various common faults for three-phase induction motors, presenting an initial study on integrated protection system for high-voltage three-phase induction motors.Finally programming the faults detection software package with Visual c++ language which implementing the following functions: automatic rotor faults detection and trend analysis of airgap eccentricity faults.