Understanding Line Losses and Transformer Losses in Rural Isolated Distribution Systems

Rural, isolated power systems in the mainland United States and in states like Alaska and Hawaii are powered by assets like diesel generators. These rural, isolated power systems cannot operate at the higher band of medium voltage (like 69 kV). They primarily operate in the 12-14 kV range to keep the cost of the distribution investments lower. Because of this mid-band medium-voltage range, the diesel consumption from line losses and distribution transformer losses is significant (almost 10% of the peak load). This work considers one such isolated power system and presents key findings about online losses and transformer losses. Understanding and documenting the impacts from losses is critical for communities that operate these power systems so they can take actions to reduce expensive diesel consumption. In this paper, we will present one such typical grid and model it in the electromagnetic transients domain. We used the tower structure and underground cabling installation to develop high-fidelity models of the lines. We also used high-fidelity models of distribution transformers to present the no-load losses and full-load losses. We present technical solutions that are available commercially off-the-shelf to reduce losses and reduce diesel consumption. This work will be a primer for communities to understand the technical challenges and possible solutions for rural, isolated power system operators.