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Location

This example model can be found in the software under the category "Conventional Generation" with the file name "Subsynchronous_Resonance_IEEE_2.ecf".

Description

The Subsynchronous Resonance IEEE 2 model is developed in HYPERSIM based on the IEEE Transactions on PAS. Second Benchmark Model for Computer Simulation of Subsynchronous Resonance

A multi-mass synchronous machine is connected to a series-compensated network. The series capacity is designed to reduce 55% of the nominal inductance of the transmission line and lower voltage drop on the line. The shaft system is critically damped.

During network disturbances, natural frequencies of the shaft are excited, generating shaft oscillations that lead to severe damage of shaft and turbine material.

The mass damping of mass #1 is 1.408. It has been increased to reach steady-state. Replace it prior to applying the fault.

System #1,
Case #1A is reproduced. Exciter mass is included in generator mass.

The steam turbine, for efficiency reasons, is built with many pressure stages: Exiter mass#1; Generator mass #2; Trbine LP mass #3; Exciter HP mass #4

The three theoritical oscillation modes of the shaft are obtained by the calculation of eigenvalues of the shaft system matrix, i.e.: 24.65 Hz, 32.39 Hz and 51,10 Hz.

Loadflow results are applied to set initial conditions to the model.

Simulation and Results

Loadflow results for initialization are presented below.

Generation buses:

Internal voltages at generation buses

In this scenario, a fault is applied after 0.0223 seconds. The system in steady-state until the fault is stable. At the fault, current peak occur and and frequency components of current start oscillating in resonance with the shaft system. This can cause critical damage as the system continues oscillating after the fault is cleared at t = 0.0393 seconds.

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In figure below, generator angle speed and spectral density of speed variation from nominal speed are presented over a period of 5 seconds after the current fault is cleared. The measured speed densities have one peak at frequency 24.6 Hz which are close enough to the first theoretical oscillation mode leading the shaft system to enter in mechanical resonance.

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References

[1] "Second Benchmark Model for Computer Simulation of Subsynchronous Resonance," in IEEE Transactions on Power Apparatus and Systems, vol. PAS-104, no. 5, pp. 1057-1066, May 1985, doi: 10.1109/TPAS.1985.323456.

See Also

Synchronous Machine (pu Standard), TGOV1, SCRX, PSS1A, PSS4B