Paper Machine 2: power transformer nonlinear loading and harmonic distortion

Paper Machine 2: power transformer nonlinear loading and harmonic distortion
Daniel Henderson
BEng (Hons) Electrical Electronic Engineering
Newcastle College University Centre

The essential, increased use in electronic devices in industry has provided versatility and energy saving potential in the form of Variable Frequency Drives. However, the impact this has on the electrical network needs to be incorporated in the design of the circuit. When not considered, the effect can be high running temperatures on power transformers, resulting in rapid ageing, as demonstrated in this report with respect to Paper Machine 2 Dry End Supply Fan power transformer, which fails catastrophically at approximately ten-year intervals. As the Electrical Duty Holder, the author had responsibilities to ensure a safe and stable electrical supply to the site, enforcing the requirement of the project.

The research and investigations conducted within the project identified that the cause of the failures was due to overloading and harmonic distortion caused by non-linear loading effects of the design, a late 1970’s DC drive application. Mitigation methods were researched and proposed to the business, who opted to fund the installation of Active Harmonic Filtration (AHF). The results were positive, with a measured reduction in harmonic distortion and
theoretical loading.

KEY WORDS: Active Harmonic Filter (AHF), Power Quality (PQ), Power Transformer,
Total Harmonic Distortion (THD), Variable Frequency Drives (VFD’s)