Handling excessive third harmonics in utility systems due to proliferation of non-linear loads

The increase in penetration and usage of harmonic rich loads can be expected to contribute to increased harmonic levels in distribution systems. The combination of the unbalanced nature of residential loads and usage of wye-wye service transformers means one can expect to see a continued increase in third harmonic levels in utility distribution systems. Also, the harmonic impact can be further exacerbated by the presence of reactive compensation in the form of capacitor banks on some feeders. This paper focuses on real-world problems related to excessive third harmonic levels in utility systems and the ways to address them. A real world case study that dealt with the failure of metal-halide lighting in a sports stadium at a public school due to excessive third harmonic levels in a utility feeder serving the load is presented. Several potential solutions to solve the problem were studied and the most suitable one was identified.