Flicker

Power Quality in the German Transmission System — Large-Scale Monitoring, Correlation Analysis, and Long-Term Forecasting

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85 IEC 61000-4-30 Class A monitoring sites across 50 substations in the German transmission system — 38 at 110 kV, 21 at 220 kV, 26 at 380 kV. Hierarchical clustering reveals which sites are redundant and which are uniquely informative. Ensemble forecasting of weekly 95th-percentile PQ parameters outperforms any individual model. The first dataset to demonstrate systematic, recurring PQ correlation structures at transmission level driven by inverter-based generation.

AI Data Centres and Power Quality — A New Category of Grid Disturbance

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AI training clusters create a load type that did not exist when power quality standards were written: synchronised GPU operation producing oscillatory load signatures with 10+ MW/second ramps, harmonic THD exceeding 5%, and simultaneous UPS disconnection risk of 2+ GW in dense data centre corridors. A real Dominion Energy grid event was triggered by a data centre producing a voltage sag at precisely once per second. Three open-access papers from 2025–2026 document the scale of the problem and the mitigation approaches now being required by grid operators.

Flicker Compensation Case Study

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A Belgian radiator factory with six welding production lines generated Pst flicker values of 1.6 — more than twice the utility-demanded limit of 0.7. Six Active Harmonic Filter units providing 2.1 MVAr total continuous reactive compensation reduced flicker to consistently below 0.63, independently verified. AHF response time was the decisive factor over SVC — it tracks the actual welding current waveform in real time.

STATCOM Case Study

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Europe’s largest steel wire producer faced a tightened flicker limit from the utility as local grid usage increased. Spot welders from Schlatter AG produced flicker emissions exceeding the new limit. A STATCOM installation reduced flicker to compliant levels — the case documents the assessment methodology, STATCOM sizing, and before/after measurement results.

Active Harmonic Filters In Printing Applications

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Amsterdam printing company producing 1 million papers daily with presses running almost continuously experienced PQ problems manifesting as production downtime and fluorescent lighting interference. Active harmonic filter installation reduced current THD, stabilised voltage, eliminated the lighting flicker, and reduced measured downtime. Before/after voltage waveform comparison shows the improvement.

Voltage Fluctuations and Flicker (John Wiley & Sons, Ltd)

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IEC flicker prediction methodology applied to the connection of a new three-phase welding machine to an existing 15 kV network. The study uses simplified assessment methods from IEC 61000-3-7 to evaluate whether the new load will cause the Pst limit to be exceeded at the PCC — a planning tool for utilities evaluating new industrial connection requests.

Low voltage (Microplanet Technology Corp.)

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An Australian utility serving remote outback areas via Single Wire Earth Return systems faced severe power quality complaints — lights flickering, unstable voltage, and very low voltage levels at remote customers. MicroPlanet’s Low Voltage Regulator restored voltage stability and reduced flicker to acceptable levels in areas where traditional network reinforcement was not economically viable.

ADF STATCOM Reduces Flicker at WDI (Comsys AB)

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WDI (Westfälische Drahtindustrie) — Europe’s largest steel wire producer — installed an STATCOM at Salzgitter, Germany, after a tightened flicker limit was imposed by the utility. Spot welders producing abrupt current pulses were the source. The STATCOM’s fast reactive current injection reduced flicker Pst from non-compliant to below the new limit.

Periodical Instantaneous Voltage Drop (HIOKI)

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Two weeks of monitoring at a Japanese retail store 100V outlet recorded periodic instantaneous voltage drops every 13 minutes — a pattern too regular to be random grid events. Analysis confirmed the cause was an electronic device on the same circuit cycling automatically every 13 minutes. Classic example of customer-caused periodic voltage fluctuation mistaken for a utility supply problem.

PQ-SVC System Solves Voltage Sag Problems for Manufacturer and Other Users of Utility Substation

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A manufacturer of muffler hangers added large automated welders — producing a 12-cycle, 4% voltage sag at 30-second intervals that caused utility complaints from all circuits at the same substation. The utility faced an impossible choice: lose the 200-employee manufacturer or continue receiving complaints from all other customers. American Superconductor’s PQ-SVC resolved both problems simultaneously.

Liquid and Gas Pump/Pipeline Applications (American Superconductor)

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Pipeline pump stations are moving to larger motors — 4160V in the 2,000–4,000 HP range, 15kV-class at 8,000–15,000 HP — creating significant flicker, harmonic, and reactive power management challenges. American Superconductor’s PQ-SVC system provides dynamic reactive compensation enabling larger motor sizes at existing substations without requiring substation upgrades.

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