Power quality describes how clean and stable the electrical supply is — and poor power quality causes nuisance tripping, overheating, premature equipment failure, flickering lights and wasted energy. A standard multimeter shows you a voltage at one instant; a power quality analyser or logger records voltage, current, power, harmonics and events over time, so you can find the cause of intermittent and load-dependent problems that a spot reading will always miss.
The common power-quality problems
| Problem | What it is | Typical symptom |
|---|---|---|
| Harmonics | Distortion from non-linear loads (drives, electronics, LED). | Overheating neutrals, transformers and motors; tripping. |
| Sags / dips | Short drops in voltage. | Resets, dropouts, contactor chatter. |
| Swells / over-voltage | Short rises in voltage. | Stressed and failing equipment. |
| Unbalance | Unequal voltage/current across three phases. | Motor overheating and loss of efficiency. |
| Transients | Very fast voltage spikes. | Damaged electronics, unexplained failures. |
| Poor power factor | Reactive load drawing current that does no work. | Higher demand charges, wasted capacity. |
Why you need a logger, not a snapshot
Most power-quality problems are intermittent or load-dependent — they appear when a big machine starts, at shift change, or only at certain times. A spot measurement almost never catches them. A power logger records continuously over hours, days or weeks, time-stamps every event, and lets you correlate a fault with what the load was doing at that moment. That correlation is what turns "it trips sometimes" into a diagnosed root cause.
What an analyser measures
- Voltage and current on each phase, plus neutral.
- Real, reactive and apparent power, and power factor.
- Harmonics (THD and individual orders).
- Sags, swells, transients and interruptions, with time stamps.
- Energy consumption over the logging period.
Where it pays off
- Troubleshooting: find the cause of nuisance tripping and equipment failures.
- Energy: identify poor power factor and wasted energy to target savings.
- Commissioning / disputes: document supply quality, verify after a fix, or support a claim with the utility.
Unitest Instruments supplies Fluke power quality analysers and three-phase loggers, available to buy or rent for a logging campaign — and our engineers can carry out the study and report for you.