Minimizing maintenance costs in a skyscraper by mitigating harmonics

Challenges at the customer’s building

The central district cooling plant at the site has a significant amount of variable frequency drive loads. These VFDs are feeding the chillers, compressors, pumps, and other loads. The customer reported several issues which are commonly associated with poor power quality, such as burning of electronic cards, excessive heating of transformers, and replacement of VFDs.

Knowing that VFDs create significant harmonic current distortions, a power quality audit was performed initially on one of the several transformers by Distinguished Resources Company (DRC), Merus Power’s local distribution partner. The power quality audit showed that the Total Current Harmonic Distortion (THDi%) at the site was as high as 23%, clearly higher than allowable limits.

Our Merus^® Solution

Based on the measurements, a power-quality solution was sized to bring the high current values below the desired limits. Merus^® A2-series Active Harmonic Filter solution built in an IP21 cabinet was shipped from the factory. Merus Power’s local partner Distinguished Resources Company installed the Merus^® Active Harmonic Filter parallel to the loads in a closed-loop configuration. Active Harmonic Filtering solution was configured during commissioning selectable harmonic mitigation mode to cancel 5^th, 7^th, 11^th, and 13^th harmonic currents.

Results after installation

Post-commissioning measurements proved that Merus^® Active Harmonic Filter has brought the Total Harmonic Distortion Current (THDi%) under 5%, thus successfully helping to comply with IEEE-519 2014 power quality standards.

All individual harmonics which were exceeding the limits such as 5^th, 7^th, 11^th, and 13^th were also reduced to a minimum. Successful commissioning and compliance ensured that the electronic cards operate under ideal conditions with sinusoidal waveform, transformer losses are minimized, and overall reliability of the electrical equipment is maintained at desired levels.