Construction function-based short-circuit fault diagnosis method for turbogenerator rotor windings

Abstract

Disclosed is a turbine generator rotor winding short circuit fault diagnosis method based on a structured function. The no-load electrodynamic potential of an electric generator is obtained according to the state variable when the electric generator operates normally, the no-load electrodynamic potential is reduced to the grid frequency of 50 Hz, and the function of a no-load electrodynamic potential reduction value relative to exciting current is built according to a curve fitting method. When fault diagnosis is carried out, firstly, the no-load electrodynamic potential is calculated through the actually measured state variable of the electric generator and is reduced to the grid frequency of 50 Hz, the no-load electrodynamic potential is compared with the no-load electrodynamic potential reduction value obtained by the structured function, a fault criteria value is obtained, and whether a rotor winding turn-to-turn short circuit fault exists on a turbine generator or not is determined by comparing the fault criteria value and a set threshold value. The turbine generator rotor winding short circuit fault diagnosis method is high in diagnosis efficiency, the health state of a rotor winding can be monitored on line and can also be analyzed off line, and the method has the great significance on preventing the fault from worsening, decreasing economic losses and improving the stability of a power system.

Description

technical field [0001] The invention relates to a method capable of on-line diagnosing whether there is an inter-turn short circuit fault in the rotor winding of a turbogenerator, and belongs to the technical field of generators. Background technique [0002] In recent years, the inter-turn short-circuit faults of the rotor windings of turbogenerators have occurred frequently, especially for the 600MW main power models that are commonly used in power systems. At present, there have been many reports of inter-turn short-circuit faults of the rotor windings. Taking a certain province as an example, from 2007 to 2010, there have been 9 large turbogenerators with rotor winding turn-to-turn short-circuit faults, of which 7 are large generators above 600MW, and two are 400MW generators. machine. In 2009, three cases occurred within one year; in 2010, five cases occurred within one year. Turn-to-turn short-circuit faults in rotor windings seriously affect the smooth completion of...

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Problems solved by technology

However, this method has the following disadvantages: ① When the generator is loaded, the leakage magnetic field of the stator winding interferes with the signal of the detection coil, which is especially serious when the generator is heavily loaded, causing the fault to be unclear and the sensitivity of fault identification to drop sharply; ② The steam turbine The rotor slot of the generator is narrow and deep. When the inter-turn short-circuit fault of the rotor winding occurs at the bottom of the rotor slot and the number of short-circuit turns is small, the influence on the leakage flux of the slot is limited, which is not enough to form obvious fault characteristics. Suitable for detection of minor rotor winding turn-to-turn short-circuit faults occurring at the bottom of the slot

③The coil detection method usually requires professional technicians to judge whether there is an inter-turn short-circuit fault of the rotor winding by observing the waveform of the detection coil. There is a long delay from the occurrence of the fault to the judgment of the fault. In fact, it cannot be regarded as a real-time fault detection method.

[0006] The fault diagnosis method for inter-turn short circuit of turbogenerator rotor winding based on shaft voltage is currently limited in scope. Although its effectiveness has been proved in field fault examples, due to factors such as environmental pollution, high sliding contact speed between carbon brush and shaft, etc. Influenced by the impact, there may be unreliable contact between the carbon brush and the shaft, which requires regular cleaning and maintenance

[0007] In a word, although the on-line detection of inter-turn short-circuit fault of the rotor winding of the turbogenerator is paid much attention at present, there are still some deficiencies in the application of various existing diagnostic methods. It is not uncommon to find out in time and cause serious consequences, so it is necessary to further improve the diagnosis level of such faults

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