Effects of Approximate Residential Distribution System Models on Power Systems Analysis

A secondary feeder model is traditionally not included in power distribution system analysis. A large share of distributed energy resources are located on the secondary side, and most power quality issues in the distribution system are associated with the secondary networks requiring complete models. In the absence of sufficient measurements and appropriate model data, secondary models are often represented using approximate models. This paper evaluates three approximate distribution system models: with no secondary, using single-phase equivalent for balanced split-phase, and a detailed unbalanced split-phase model for residential distribution systems, using IEEE 8500-node test system. The results demonstrate that the case with no secondary and using a single-phase equivalent model cannot correctly reflect the operations of voltage regulators. Any approximate models cannot capture the degree of unbalanced in the secondary network. Approximation of an unbalanced split-phase residential distribution system with the balanced split-phase model can provide reasonably accurate calculations of total losses and primary voltage estimations.