Method and system for monitoring sub-synchronous oscillation (SSO) and torsional vibration of shaft system of steam turbine generator unit

Abstract

The invention belongs to the technical field of monitoring of torsional vibration of shaft systems of steam turbine generator units and particularly relates to a method and system for monitoring sub-synchronous oscillation (SSO) and torsional vibration of a shaft system of a steam turbine generator unit. The method comprises the steps that the mode of mechanical-side monitoring first and electrical-side monitoring second is adopted, real-time torsional stress of all torsional vibration dangerous sections of the shaft system is monitored, and whether sub-synchronous components exist in electrical signals is monitored; when mechanical-side torsional stress exceeds a torsional vibration alarm threshold value or the sub-synchronous components are monitored in the electrical-side electrical signals and exceed the SSO threshold value at which the sub-synchronous components can stimulate the shaft system, it is judged that SSO happens to the shaft system of the steam turbine generator unit; meanwhile, the method for determining an alarm threshold value, a damage alarm threshold value, a tripping protection threshold value and a sub-synchronous component threshold value for judging whether SSO happens to the shaft system of the steam turbine generator unit is given. By the adoption of the method and system, online monitoring, analysis and protection of SSO can be achieved, and meanwhile torsional vibration fatigue life loss of the shaft system of the steam turbine generator unit can be calculated accurately.

Description

technical field [0001] The invention belongs to the technical field of torsional vibration monitoring of a turbogenerator shafting system, and in particular relates to a method and system for monitoring the torsional vibration of a turbogenerator shafting Sub Synchronous Oscillation (Sub Synchronous Oscillation, hereinafter referred to as SSO). Background technique [0002] The torsional vibration of the shafting of the turbogenerator can be divided into transient shock torsional vibration and subsynchronous oscillation and other resonance torsional vibration according to its excitation mechanism. The series capacitance compensation of the power transmission system, DC transmission, improperly installed power system stabilizers, and the feedback effects of the excitation system of the generator, the thyristor control system and the electro-hydraulic regulation system, etc., may induce SSO, which directly threatens the unit safe and reliable operation. When SSO occurs in the...

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Problems solved by technology

[0003] In general, the main source of fatigue life loss caused by SSO to the shafting is the small alternating torsional stress exceeding the torsional fatigue limit of the rotor steel material. The fatigue life loss caused by a single stress cycle on the shafting is often small, but due to The shafting has to withstand more than 10 stress cycles per second, and the fault lasts for a long time. If the fault is not suppressed in time, the cumulative fatigue life loss caused by SSO to the shafting may be more serious than when a large disturbance occurs. Especially when SSO shows a trend of continuous divergence, the cumulative fatigue life loss of shafting may reach 100% in a short period of time. Therefore, real-time monitoring of SSO can detect SSO in time so that relevant measures can be taken to suppress SSO development to avoid more serious damage to the unit

[0004] It is difficult for the existing monitoring methods to accurately obtain the small changes of the three-phase current and voltage of the generator. When the subsynchronous oscillation fault occurs in the unit, the small current and voltage fluctuations of the generator may not be accurately monitored. At this time, the generator electromagnetic The change of torque is enough to excite the resonance of the shafting of the unit

In this case, the accuracy of the model simulation method is limited and cannot meet the needs of torsional vibration monitoring. Therefore, it is necessary to use the method of modal superposition to monitor resonance faults such as subsynchronous oscillation.

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