GIPA 115kV Interconnection Evaluation

CHA has worked on several Green Island Power Authority (GIPA) projects as demand continues to grow. GIPA serviced nearly 1,400 customers and had a peak demand of 6.5 MVA versus a peak capacity of 7.5 MVA. The area that GIPA served had seen significant load growth over past years, and current projections for new load indicated a need to upgrade GIPA’s existing system capacity. GIPA negotiated with National Grid to upgrade its 34.5kV sub-transmission circuit to allow a peak capacity of 15 MVA. These negotiations resulted in a new interconnection agreement between GIPA and National Grid. 

To accommodate the additional capacity, GIPA had to expand their existing 34.5-4.16kV distribution substation. The expansion removed one old transformer and installed two new transformers to increase transformer capacity to serve industrial/commercial and residential customers, along with associated voltage regulators, circuit breakers, reclosers, relaying, controls, and substation infrastructure.

Based on inadequate reliability with a 34.5kV interconnection, projected load growth, and plans to upgrade the GIPA hydroelectric plant’s capacity, CHA/GIPA approached National Grid with a proposal for a new 115kV interconnection as part of the project’s second phase, which included:

  • 115kV line tap of the existing National Grid Maplewood-Johnson Road transmission line
  • 115kV – 34.5kV substation adjacent to the Norlite property
  • Underground 34.5kV line from the new substation to current GIPA 34.5kV interconnection point with National Grid
  • Reuse of existing 34.5kV overhead line from existing 34.5kV interconnection point to existing GIPA 34.5kV distribution substation
  • Underground 34.5kV from the existing GIPA hydroelectric station to the existing GIPA 34.5kV distribution substation (potential future project based on hydroelectric expansion)