Abstract:
The Synchronous Condenser Unit 3 (SC3), in charge of adjusting the electric power between the hydroelectric generating facility and the transmission grid, experienced undesirable vibration levels during its initial stages of operation. The source of the high vibration levels is attributed to the resonant dynamic interaction between the condenser, its foundation, and the supporting soil media. The undesirable vibration was detected in SC3, and similar patterns are likely to occur for units 1 and 2 once they begin operation.
A Synchronous Condenser is a rotatory machine operating at a stationary frequency. The foundation of SC3 consists of a massive reinforced concrete block supported on steel casing piles with reinforced concrete infill.
The goals of this project are: (1) diagnose the problem, (2) identify feasible retrofit solutions, and (3) perform engineering analysis of the proposed retrofit solution. The work is divided accordingly in three stages and accomplished using rigorous Soil Structure Interaction (SSI) analysis.
A detailed three-dimensional (3D) Finite Element SSI Model is developed to accurately represent the interaction between forces, structure, soil, and foundation. The model is analyzed using the proprietary computer software SC-SASSI, including the recently implemented SC-Pile elements.
A number of possible solutions are evaluated with the objectives of: (1) reducing vibration amplitudes, (2) shifting away the system frequency from the operation frequency, which are both achieved by increasing the system stiffness, and therefore minimizing potential resonance conditions; and (3) minimizing the disruption of the surrounding critical equipment already installed.