Data Centre Power Quality Testing

Solving clients’ problems

We measure key parameters such as leakage currents, neutral-ground voltage, voltage stability, wave shape and harmonics, of the power supplied to your IT equipment in the data centre.  We then collate and analyse the data, looking for unexpected behaviour and conditions that are outside the manufacturer’s stated limits.  We attempt to track down the cause of any anomalies, and present the findings in a comprehensive report, along with any recommendations. With this information, you can plan for future upgrades, detect inappropriate connections and ensure that your system is tuned for best reliability and efficiency.

A power survey can be performed on its own or as part of a full Data Centre Environmental audit.

Power audit revealed overworked, unbalanced UPS

A graph showing 3 sine waves, red, blue and yellow.  The yellow sine wave is poorly formed, that is, a little wavy, not a smooth curve.A 7 line table - the most interesting line showing harmonics significantly exceeding recommendations.

While monitoring power we measured an unnecessarily high value of 249.2v  (maximum  allowable 253.0v) from the UPS. This was subsequently adjusted down. The load indicated that the UPS was significantly out of balance and we also noted that red phase carried twice the load of the other two. Red phase also exhibited the lowest voltage and worst harmonic distortion. In each case, the higher the indicated load, the worst were both output voltage and harmonic distortion for that phase.


Most IT manufacturers recommend that harmonic distortion (THD) does not exceed 5% on any phase. Consequences of not observing this are reduced reliability and service life of equipment.  It is notable that while some major manufacturers do allow 9% THD, they limit the third harmonic to 7% which is still exceeded here on red and yellow phases. We recommended that the client confirm that the capacity of the UPS is not being exceeded, that they confirm the accuracy of the values of current being reported and then balance loads across all three phases, that they understand the reason for a low red phase voltage if it still exists, and correct as appropriate and that they confirm that harmonics fall to below 5% on all phases.

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