Subsynchronous Resonance Tests and Torsional Monitoring System Verification at the Cholla Station

The Cholla generating station of Arizona Public Service Co. is connected to a series capacitor compensated transmission system. Extensive studies of subsynchronous resonance (SSR) interactions at this plant show the need to carefully monitor the transient torque history of the shafts. A test program was performed which verified the operation of a torsional monitoring system and measured the torsional interaction of the third torsional mode with the series capacitor compensated system. Results show that the comparison of analytical studies and field tests is very sensitive to the model used for station auxiliary load and generator subsynchronous impedance.