# Power Quality and Reactive Compensation: Capacitor Banks, SVC and STATCOM

> A project-level guide to reactive-power sizing, harmonic resonance, detuned capacitor banks, SVC/STATCOM response and IEC 61000-2-4 industrial compatibility levels.

- **Category:** Power Quality & Reactive Compensation
- **Author:** Voltformer Grid Quality Engineering
- **Publication Date:** 2026-09-08
- **Reading Time:** 9 min read
- **Key Tags:** #Power Factor Correction, #IEC 61000-2-4, #IEC 60871, #SVC, #STATCOM
- **Canonical URL:** https://voltformer.com/articles/power-quality-reactive-compensation-statcom-svc-harmonics
- **Markdown Source:** https://voltformer.com/articles/power-quality-reactive-compensation-statcom-svc-harmonics.md

### 1. Start at the Point of Common Coupling

IEC 61000-2-4:2024 gives compatibility levels for low-frequency conducted disturbances in industrial locations up to 35 kV and includes voltage deviations, dips, imbalance, harmonics, interharmonics, DC components and transient overvoltages. Measure and model the point of common coupling (PCC) before choosing a capacitor bank, SVC or STATCOM.

### 2. Reactive-Power Sizing

For a load moving from power factor cosφ₁ to cosφ₂, the ideal fundamental-frequency reactive-power step is:

$$ Q_c = P \cdot (\tan\varphi_1 - \tan\varphi_2) $$

| Equipment | Best-fit duty | Main engineering risk |
|---|---|---|
| **Contactor-switched capacitor bank** | Slowly varying, clean industrial load | Resonance, inrush and overcompensation |
| **Detuned capacitor bank** | Power-factor correction with harmonics | Reactor loss, tuning tolerance and temperature |
| **SVC** | Fast reactive-power and voltage control | Harmonic emission and filter coordination |
| **STATCOM** | Dynamic var support, weak grids and unbalance | Converter current, cooling and control interaction |

### 3. Harmonics and Resonance

IEC 60871-1 covers shunt capacitor units and banks above 1 kV, including power-factor correction and filter circuits. Capacitors must not be connected from a kWh estimate alone: calculate short-circuit strength, background distortion, converter spectrum, switching transients and the parallel-resonance point.

A screening estimate for a capacitor-bank resonance is:

$$ f_r \approx f_1 \sqrt{\frac{S_{sc}}{Q_c}} $$

Use a frequency scan and time-domain switching study for the final design, especially where VFDs, UPS rectifiers, PV inverters or arc furnaces are present.

### 4. Acceptance Data

Specify PCC voltage-quality limits, step response, kvar or Mvar range, control deadband, unbalance, harmonic current, detuning frequency, discharge time, protection and bypass behaviour. Commission with before/after recordings at the PCC and at the largest nonlinear loads.

*Reference: IEC 61000-2-4:2024; IEC 60871-1:2014; IEC 61000 series; IEEE 519-2022.*

---

## Related Equipment & Catalog Cross-References

- [Transformers Catalog](https://voltformer.com/catalog.md): Browse medium and high voltage power transformers.
- [Medium Voltage Switchgear](https://voltformer.com/catalog.md): Air-insulated (AIS) and gas-insulated (GIS) switchgear panels.
- [Protection & Control Relays](https://voltformer.com/catalog.md): ANSI 87T differential, overcurrent and feeder protection relays.
- [Machine-Readable API Catalog](https://voltformer.com/agent-catalog.json): Autonomous agent catalog data.