Evaluation of harmonic limits in large office buildings

Issues relating to the application of harmonic limits in large office buildings in Hong Kong are discussed. The characteristics of distribution systems in such buildings are outlined. The necessity for detailed evaluation, PCC selection and I_SC/I_L calculation are discussed. The significance of the use of busbar, busduct and cable risers is taken into account. The evaluations of sample buildings show that harmonic limits for the 3rd harmonics is difficult to satisfy, whilst that of other orders are generally fulfilled. Even if all tenants fulfill harmonic current limits, it is still difficult to comply with harmonic voltage limits at the building owner/tenants PCC especially when cable risers are used. Recommendations on application of harmonic voltage and current limits for large office building distribution systems are proposed