Method for distinguishing subsynchronous modal signal diffusion

Abstract

The invention discloses a method for distinguishing subsynchronous modal signal diffusion. A regular sampling frequency is adopted by a protecting device or monitoring device to collect electric quantity signals of a generator, namely three-phase currents IA, IB and IC, and a mechanical quantity signal, namely rotating speeds omega-omega0 at a big shaft end of the generator, wherein the omega0 is an average rotating speed within a time period, per-unit values of the three-phase currents are calculated and a rated current is taken as a basic value; the rotating speed signal omega is a per-unit value and a rated rotating speed is taken as a basic value; a low-pass filter and a high band-pass filter are used for filtering; a corresponding frequency of the signals and an amplitude sequence of the signals are calculated; at last, data is extracted in a fixed time interval, thereby obtaining a new amplitude sequence. The processes of criterion starting, amplitude comparison, diffusion counting and logic comparison are adopted for judging whether the modal signals are continuously increased, and if so, the modal diffusion is confirmed. The protecting device or monitoring device gives an alarm or carries out tripping operation. The method provided by the invention is simple in criterion and is easy to implement.

Description

Technical field [0001] The present invention relates to the field of power systems, more specifically to the field of generator subsynchronous oscillations in thermal power plants and nuclear power plants, and to a method for judging the continuous divergence of subsynchronous modes in generator current and speed signals and corresponding relay protection devices Or monitoring device. Background technique [0002] In my country’s “West-to-East Power Transmission”, large-scale thermal power plants are often far away from load centers and generating units have large capacity. Long-distance transmission methods are often used to send power; in order to improve transmission capacity, power grids are often equipped with series capacitor compensation and controllable series capacitor compensation. equipment. This transmission method is a typical way of electromechanical coupling to cause subsynchronous oscillation. When the equivalent damping of the electromechanical system is negative...

AI Technical Summary

Problems solved by technology

The electrical subsynchronous oscillation and the subsynchronous torsional vibration on the shaft system can cause heating, vibration, and mechanical fatigue of the main shaft. In severe cases, fatigue accumulation can cause cracks or even twisting of the large shaft on the dangerous section

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