Substation Conversion

Pella Substation

City of Pella Improves

Electrical Reliability

Missouri River Energy Services Adds
Interconnection at Pella's West Substation

Project Owner:
City of Pella, IA

Key Experience:

  • Multi-phase construction
  • Coordination among multiple stakeholders

Key Features:

  • 28 MW of local generation
  • Three existing 69 kV transmission terminals
  • Reconstruction required to continue to serve existing load

The City of Pella, Iowa identified a need for additional 15 kV distribution feeders at their West Substation. The existing substation was a single 69 kV bus arrangement, with three 69 kV transmission line terminals, one power transformer and associated 15 kV distribution switchgear. Also included was a generator step-up transformer with a 15 kV generation switchgear bus, and a 69 kV capacitor bank.

Missouri River Energy Services (MRES) is installing 55 MW of hydroelectric generation at the Red Rock Reservoir on the Des Moines River near Pella, and needed access to the transmission grid for the generation output. MRES requested a 69 kV point of interconnection at Pella’s West Substation.

The existing bus arrangement at the West Substation could not support another 69 kV transmission line terminal. Pella contracted with DGR Engineering to develop different substation bus plans and cost estimates to accommodate the new 69 kV point of interconnection for MRES and a new power transformer and 15 kV distribution switchgear for the Substation.

DGR Engineering developed multiple conceptual substation layouts and cost estimates for the proposed substation. The City of Pella opted to proceed and construct a six position 69 kV ring bus plan. The selected plan would increase the reliability of West Substation and provide the City of Pella with additional distribution feeders, and provide MRES with a 69 kV interconnection.

One of the challenges of the proposed ring bus was maintaining service to the existing power transformer serving the distribution switchgear. The construction of the 69 kV ring bus was staged in multiple phases to accommodate this requirement. In addition, the step-up transformer for the generation switchgear was repurposed to provide additional capacity for a new 15 kV distribution switchgear.