The SHEI (Sheffield Highgate Export Interface) is an ISONE defined transmission region in northern Vermont. A VELCO-owned 115kV transmission line from Sheffield to Highgate to St. Albans and a GMP owned 34.5kV subtransmission line from VELCO East Fairfax to Lowell make up the region. Around 21,500 VEC members are fed off of these transmission lines and the area has significantly less load than generation. 

Since the load in the region is often low (spring and fall) when generation from Wind and Hydro tend to be high there is excess generation that needs to flow out on the transmission system. The capacity of this transmission (originally designed to meet the load) limits its ability to export the power to the rest of Vermont and New England and as a result projects are curtailed (shut down or limited generation).

VEC is recommended that any new generation should be located outside of the SHEI. A map has been developed to assist in the locating of generation: Click here.