What is IEC 61000-4-30, and what do Class A, Class S and Class B mean?
IEC 61000-4-30 specifies how power quality is measured, not what the limits are. Limits come from other standards, grid codes and contracts. Its goal is repeatable, comparable results: two compliant instruments measuring the same supply should report the same values.
What it covers
- Power frequency
- Magnitude of the supply voltage
- Flicker
- Voltage dips, swells and interruptions
- Transient voltages
- Voltage unbalance
- Harmonics and interharmonics
- Mains signalling voltage
- Rapid voltage changes
Measurements are made over defined intervals. A basic 10/12-cycle interval (50/60 Hz) is aggregated into 150/180-cycle, 10-minute and 2-hour values. Harmonics and flicker are measured using the methods of IEC 61000-4-7 and IEC 61000-4-15.
Class A, Class S and Class B
| Class | Intent | Typical use |
|---|---|---|
| Class A (advanced) | Strictest requirements for measurement methods, accuracy and time synchronization, so results are comparable between instruments. | Contractual and dispute resolution work, and verifying compliance with standards or regulations. |
| Class S (surveys) | The same parameters and measurement methods, with less demanding performance requirements than Class A. | Statistical surveys, power quality assessments, monitoring and troubleshooting where results do not need to be strictly comparable. |
| Class B (legacy) | Retained for existing equipment. It was moved to an informative annex in the 2015 edition and removed in the 2025 edition. | Older instruments only. New designs target Class A or Class S. |
Choosing a class: if a result may be used to settle a dispute or demonstrate regulatory compliance, specify Class A. For surveys, trending and troubleshooting, Class S is usually sufficient. Always check which edition and class your contract, grid code or regulator refers to.
How Yokogawa instruments fit in
- Power quality monitoring: the CW500 Power Quality Analyzer conforms to IEC 61000-4-30 Class S. It records voltage dips, swells, interruptions and transient overvoltages with occurrence time and waveform, and measures harmonics (up to the 50th order), flicker (Pst and Plt) and voltage and current unbalance.
- Harmonic and interharmonic measurement (IEC 61000-4-7): the WT5000 supports harmonic grouping, interharmonics and the 2 kHz to 9 kHz range of Annex B, with harmonics up to the 500th order. The WT1800R also measures harmonics up to the 500th order with IEC 61000-4-7 harmonic grouping.
- Equipment emissions testing: the WT5000 with the /G7 option and IS8000 software (harmonic current and voltage fluctuation/flicker measurement) can be used for IEC 61000-3-2 harmonic current and IEC 61000-3-3 voltage fluctuation and flicker tests.
Harmonic measurement by model
| Capability | WT5000 | WT1800R | WT300E |
|---|---|---|---|
| Harmonic and interharmonic measurement | |||
| Core power parameters (voltage, current, power, power factor, frequency) | ✓ | ✓ | ✓ |
| Maximum harmonic order | 500 | 500 | 50 |
| Voltage and current harmonics, THD | ✓ | ✓ | △ Optional |
| IEC 61000-4-7 harmonic grouping | ✓ | ✓ | △ Optional |
| Interharmonics | ✓ | △ Limited | ✗ |
| IEC 61000-4-7 Annex B (2 kHz to 9 kHz) | ✓ | ✗ | ✗ |
The WT300E covers the core power parameters, with harmonic functions available as an option. Key: ✓ = supported; △ = supported with a condition; ✗ = not available on that model.
Also see How many orders of harmonics can Yokogawa power analyzers measure?
Related Products & Solutions
CW500 - Power Quality Analyzer
The Yokogawa CW500 is a portable power analyzer that logs transient power phenomena in addition to measuring single to three phase power.
WT1800R High-Performance
- Up to 6 wattmeters
- 0.05% of rdg + 0.05% of rng
- DC, 0.1Hz to 1MHz
- 2 motor inputs
- Harmonics to 500th order
WT300E - Economy
- Up to 3 wattmeters
- 0.1% of rdg + 0.05% of rng
- DC, 0.1Hz to 100kHz
- Standby Power, Energy Star®, SPEC Power® and IEC62301/EN50564
WT5000 - Highest Precision
- Up to 7 wattmeters / Modular
- 0.01% of rdg + 0.02% of rng
- DC to 1MHz
- 4 motor inputs
- Harmonics to 500th order
- IEC 61000 compliance testing