Measure first
Power quality surveys
Capacitors, filters and drive changes are expensive to get wrong. A survey records what your electrical system actually does over a normal operating cycle, so the fix matches the problem.
When a survey is worth it
- Before buying power-factor correction for a plant with drives or other electronic loads.
- When equipment trips, overheats or fails without an obvious cause.
- When the utility raises a power-factor, harmonic or flicker question.
- Before adding large drives, welders or motors to an existing service.
If the only question is "does my utility charge for power factor?", you don't need a survey. A bill review answers that.
What gets measured
| Quantity | Why it matters |
|---|---|
| Voltage and current on each phase, and unbalance | Loading, voltage drop, unbalance that heats motors |
| kW, kVAR, kVA; displacement and true power factor | Capacitor sizing, and whether correction can help at all |
| Harmonic voltage and current, individual orders and THD/TDD | Resonance risk, detuning, IEEE 519 at the point of common coupling |
| Sags, swells, interruptions and transients, with timestamps | Matching trips and failures to electrical events |
| Flicker (Pst/Plt) | Light flicker complaints, welding and cyclic loads |
| Demand profile over time | Load range for switched capacitor steps; peak vs light-load behavior |
For utility comparisons or IEEE 519 evaluation, specify IEC 61000-4-30 Class A measurement methods, IEC 61000-4-7 harmonic measurement methods, and the IEEE 519 aggregation and statistical reporting. Confirm the analyzer's supported functions, harmonic range, event capture and voltage/current transducer accuracy. IEC 61000-4-30 conformity alone does not establish IEEE 519 compliance.
How long and where
A survey usually runs for about a week, so it captures weekday and weekend operation, shift changes and light-load nights, when leading power factor and resonance problems tend to show up. For capacitor sizing, measure the service entrance and relevant feeders. For IEEE 519 evaluation, confirm the point of common coupling with the utility and measure there; it may be a different location from the service entrance.
What a survey scope should include
Before commissioning a survey, agree these deliverables with the survey provider:
- A plain-language summary of findings, with the supporting charts.
- Load and power-factor profiles, and the kVAR range a correction system would need to cover.
- Harmonic levels and an assessment of resonance risk with capacitors.
- Recommendations ranked by cost and effect. Sometimes the answer is "no correction needed".
Getting started
Send us 12 months of bills and a short description of the plant and any symptoms. We'll discuss whether a survey is warranted, what it should cover and how it can be arranged.