Wolverine Power Supply Cooperative

Transient Stability in Power System Analysis

Wolverine Power Supply Cooperative (WPSC) engaged Commonwealth to conduct a comprehensive system impact study for the interconnection of a third-party generator (IPP) near Kalkaska, Michigan. The IPP aims to generate approximately 50 MW of peaking power and connect to WPSC’s South Boardman-Alba 68 kV transmission line via a single-circuit tap approximately 2,300 feet in length.

Commonwealth conducted a transient stability power system study for the new generation addition using the SDDWG/ECAR model, which was modified to include details of the new substation. The plant has a maximum capability of 60 MW. The specific case studied involved a fault on the line near the plant, which was cleared by opening the line.

The system has a critical clearing time of only four cycles for the close-in three-phase fault. Assuming a normal clearing time of six cycles, 60 MW of new generation would not be stable for this three-phase fault. However, the system is stable for a single-line-to-ground fault.

A sensitivity analysis was performed to determine the critical clearing time for the plant at a nominal 50 MW. At 50 MW output, the critical clearing time is six cycles.

The studies were conducted using Commonwealth’s TRANSMISSION 2000® Power Flow and Transient Stability programs, which can solve the largest available models, currently more than 50,000 buses.

This study highlights the importance of understanding the stability and reliability of power systems when integrating new generation sources. By conducting thorough analyses and using advanced modeling tools, WPSC and Commonwealth can ensure the safe and efficient operation of the power grid.