Wolverine Power Supply Cooperative
Wolverine Power Supply Cooperative (WPSC) contracted with Commonwealth to provide a system impact study for the interconnection of a third-party generator (IPP) near Kalkaska, Michigan.
The IPP intended to generate approximately 50 MW of peaking power and connect to WPSC’s South Boardman-Alba 68 kV transmission line with a single-circuit tap approximately 2,300 feet in length.
Commonwealth performed a transient stability study for the addition of the new generation using the SDDWG/ECAR model, modified to include details of the new substation. The plant has a maximum capability of 60 MW. The specific case studied was that of a fault on the line near the plant and cleared by opening the line.
The system has a critical clearing time of only 4 cycles for the close-in three-phase fault. Assuming a normal clearing time of 6 cycles, 60 MW of new generation would not be stable for this three-phase fault. 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 nominal 50 MW. At 50 MW output, the critical clearing time is at 6 cycles.
The studies were performed using Commonwealth’s TRANSMISSION 2000® Power Flow and Transient Stability programs. These programs are capable of solving the largest available models, presently more than 50,000 buses.