Steel, textile, 汽车, printing, food, chemical, glass, machine shops
Voltage swells (1.1–1.8 pu, 0.5 周期来 1 分钟) cause MOV failures, VFD过压跳闸, 绝缘应力, and PLC reboots — often with delayed, hidden damage. Three causes: SLG fault on ungrounded MV (max 1.73 pu on healthy phases), large load rejection, and capacitor bank switching. PT. PLN Sibolga field case: 3-phase fault produced 1.724 pu swell on phase A — DVR reduced to 0.997 pu simultaneously with sag recovery on phase C.
Interharmonics — frequency components that are not integer multiples of the fundamental (例如，. 75 赫兹, 130 Hz on a 50 Hz system) — are produced by PV inverters, wind turbines, 电动车充电器, cycloconverters, and HVDC links. Their most dangerous effect: an interharmonic at 58 Hz creates an 8 Hz beat frequency — squarely in the range of peak human visual sensitivity. Field case: simultaneous PV + EV charger + microwave on one LV circuit produces stochastic interharmonics causing light flicker. Standard IEC 61000-4-7 analysers cannot correctly characterise them.
Four documented negative effects of supraharmonic distortion (2–150 kHz) on MV and LV distribution networks: power loss and heating from skin effect, dielectric material aging at accelerated stress cycle rates, MV cable termination failures from combined dielectric stress and local heating, and PLC interference in smart metering and demand response systems. Key finding: MV/LV transformer transfer ratio is 0.5–3.0 — some supraharmonic components are amplified crossing from MV to LV. Strong correlation measured at substations 16 km apart. No planning or compatibility limits currently exist above 9 千赫.
Mirus International demonstrates why DOE 2016 transformer efficiency ratings miss the mark for harmonic-rich environments. Weighted average loading at harmonic-producing loads requires adjusted efficiency equations — the ULLTRA transformer design achieves high efficiency across the full load spectrum, not just at nameplate rating.
Mirus International demonstrates that generators feeding non-linear loads must be derated or oversized to prevent excessive voltage distortion — standard practice adds 20–25% generator capacity. The Wide Spectrum Filter (Lineator) eliminates the oversizing requirement by reducing harmonic current drawn from the generator, enabling right-sized generator selection and significant capital and fuel savings.
Long cable VFD applications produce cable resonance that amplifies dV/dt at the motor terminals — causing insulation stress and premature motor failure. A dV/dt filter limits the voltage rise rate but does not produce a true sine wave. A sinewave filter eliminates both the resonance and the harmonic content. Field comparison at San Antonio Water Authority shows measured motor terminal voltage for both filter types.
IEEE conference paper by Prof. José Carlos de Oliveira (Federal University of Uberlândia) — site measurements at a Brazilian textile factory. Four-parameter framework: voltage profile, 谐波失真, 电压不平衡, and feeder transfer risk. A foundational industrial PQ assessment methodology paper. The PDF is available for download from the IPQDF library.
A steel mill with variable speed drives experienced frequent VSD tripping with “过电压在AC线路” indication despite normal steady-state voltage. Utility-induced switching surges — invisible to RMS voltmeters — were the root cause. Case demonstrates why true PQ monitoring with transient capture is essential in facilities with long cable runs and VSD loads.
Dual utility feeds prevented a multi-hour outage when a wind-induced fault caused a line-to-line fault at the automobile assembly plant substation — but did not prevent the 4.8-cycle voltage sag at 68% voltage that still caused process disruptions. Four GPS-synchronised monitors confirmed the fault on both transmission lines simultaneously. A DVR would have prevented the process disruptions entirely.
Non-characteristic harmonics — orders not predicted by the standard 6k±1 formula for 6-pulse rectifiers — appear in power systems with converter firing angle asymmetry, supply unbalance, or multiple overlapping non-linear loads. Schlumberger/IEEE paper presents an identification methodology using harmonic fingerprinting to detect unhealthy power systems from their non-characteristic harmonic signature.
A major food processing and distribution centre in Dortmund, Germany — 100,000 m² facility — experienced production disruptions and equipment malfunctions from harmonic distortion generated by VFDs in the highly automated facility. Active harmonic filter installation reduced current THD and eliminated the production disruptions. Before/after measurements confirm compliance with German grid code.
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.
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.
A major European manufacturer’s dynamic test bench — with highly variable loading — produced harmonics up to and beyond the 100th order plus voltage notching that corrupted test results. Active harmonic filters compensating up to the 100th order eliminated both phenomena, restoring the integrity of development testing and preventing false test failures from power supply artefacts.
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.
Saudi Arabia academic review of harmonic generation mechanisms, propagation paths, and mitigation techniques for non-linear loads — covering passive filters, active filters, hybrid approaches, and multi-pulse converters. Provides theoretical grounding for harmonic mitigation selection, with worked examples for different industrial load types. King Saud University publication.
Chemical plant using large static converters for electrochemical processes experienced repeated harmonic filter failures. Investigation revealed even harmonic resonance — an unusual problem typically found only in uncontrolled rectifiers or systems with DC offset. The even harmonics were caused by asymmetrical firing of the converter’s thyristors, creating 2nd and 4th harmonic currents that the filter was not designed to handle.
South African distribution network with two resonant points at different harmonic orders — a single-tuned filter addresses one resonance but can amplify the other. Case from Cape Peninsula University of Technology documents the filter design process for a network with two resonant frequencies, requiring a carefully detuned double-tuned filter to address both simultaneously.
A steel processing plant experienced unexplained capacitor failures and fuse operations in an automatically switched capacitor bank. Eaton Engineering investigation revealed harmonic resonance between the capacitor bank and system impedance — at a specific harmonic order, the impedance was amplified, overloading the capacitors well beyond their rated capability. Classic harmonic-capacitor resonance case with full analytical solution.
Laboratory measurements on a 2.2 kW adjustable speed drive subjected to controlled voltage dips of varying magnitude and duration. The ASD’s DC bus capacitors and ride-through capability are characterised — showing the boundary between ride-through and trip as a function of sag depth and duration. Provides the experimental basis for ASD immunity specification in sensitive industrial applications.
A steel factory in northern Italy had all laboratory electronic equipment behaving erratically — seemingly without cause. Investigation revealed constructive defects in the earthing system creating large current loops. With heavy currents flowing through the earth return path, the potential difference between equipment earths was sufficient to cause data corruption and equipment malfunction throughout the plant.
Six-pulse converter transformer selection and rating when harmonic spectrum is known. John Wiley Handbook of Power Quality chapter covers K-factor calculation, additional loss estimation, and de-rating methodology for transformers feeding rectifier loads. Provides the calculation procedure engineers need to correctly specify transformers for non-linear load environments.
IEC flicker prediction methodology applied to the connection of a new three-phase welding machine to an existing 15 千伏网络. 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.
Dynamic test bench with programmable loading patterns produced harmonics up to the 100th order and significant voltage notching. Comsys ADF Active Harmonic Filter installation reduced notching and harmonic distortion, restoring supply quality to other equipment on the same transformer. A duplicate of case 2328 with slightly different background — Comsys vs. Active Harmonic Filters branding.
REWE Dortmund distribution centre — rebuilt and expanded butcher facility with high VFD density — experienced harmonics causing machinery malfunctions. Comsys ADF active harmonic filter brought current THD within acceptable limits and eliminated the machinery problems. Duplicate of case 2336 with Comsys branding — same REWE Dortmund facility, same solution.
WDI (威斯特伐利亚电线行业) — Europe’s largest steel wire producer — installed an STATCOM at Salzgitter, 德国, 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.
01 · Context · 02 · Problem · 03 · Solution · 04 · Results · 05 · PQ Perspective · References Flicker Welding Loads Active Harmonic Filter EN 50160
Solid-state harmonic filter application in a textile manufacturing plant — reducing harmonic current injection from VFD-driven machinery. The filter also improved power factor, reducing reactive power charges from the utility. Available as an external linked technical document.
HIOKI PW3198 Channel 4 is isolated from the three voltage measurement channels — enabling DC power supply monitoring, second-circuit measurement, or neutral current measurement simultaneously with three-phase voltage. Practical measurement configurations for complex industrial monitoring scenarios.
Remote monitoring of a power quality analyser via LAN using the HTTP server function — no special software required. HIOKI PW3198 screen mirroring at 0.5 second refresh rate with password protection for setting changes. Eliminates the need for on-site technician visits during extended monitoring campaigns.
Conductive noise — high-frequency electrical disturbances spreading through power, signal, and ground cables from lightning surges, 静电放电, and high-order harmonics — causes equipment malfunction and radio/TV interference in neighbouring premises. HIOKI measurement techniques covering up to 100 MHz identify the noise frequency band and propagation path for targeted mitigation.
Power supplies with semiconductor control devices generate high-frequency noise above several kHz — high-order harmonics that cause equipment malfunction and radio/TV interference. HIOKI measurement at 1-phase 100V shows the frequency spectrum, resonance amplification effects, and the threshold at which the noise becomes dangerous to connected equipment.
HIOKI technical guide to determining whether harmonics are flowing from a facility into the grid or from the grid into the facility — the fundamental question for harmonic source attribution. Covers power direction measurement methods, Japanese utility guideline compliance assessment, and field measurement examples showing both inflow and outflow scenarios with the HIOKI PW3198.
A Southeast Asian factory on a 100V single-phase circuit experienced damaged power supplies. Two weeks of monitoring revealed large voltage fluctuations of ±50V between 9 PM and 9 AM nightly — correlated with neighbourhood load patterns. Event data confirmed voltage dips to 75 Vrms and swells to 125 有效值. Supply quality was far outside acceptable limits during off-peak hours.
Eighteen days of monitoring on a 1-phase 100V circuit recorded 68 identical waveform distortion events, subsequently classified into two types: UPS switching transients and persistent waveform noise. The systematic waveform comparison technique demonstrates how event classification reveals root cause — the UPS was not returning to sine wave output after switching.
Low-cost UPS systems sold in retail stores output square waves rather than sine waves — a fact most users are unaware of. HIOKI measurement shows voltage swells and dips at UPS switching transitions in systems without output voltage compensation. Equipment designed for sine wave supply may malfunction on square wave UPS output.
A factory 200V three-phase circuit recorded recurring transient overvoltages on all three phases simultaneously — occurring twice per fundamental cycle with 820 µs spacing, 之间 10 kHz和 30 千赫, peaking at 120–260 V. The simultaneous three-phase occurrence and precise timing pattern indicates a resonance phenomenon, not a switching event — root cause undetermined.
Equipment power supply damage traced to transient overvoltages caused by power factor correction capacitor switching within the facility. The switching waveform propagated through the LV circuit without filtering and combined with impulse transients at switch-off, creating damaging voltage peaks. A filtering device at the capacitor bank would have prevented the equipment failures.
Laboratory simulation of voltage drop caused by cable impedance — a 1Ω cable carrying 10A produces a 10 Vrms voltage drop, reducing a 100V supply to below 90V. Equipment designed to tolerate ±10% voltage variation trips when cable impedance consumes the entire tolerance margin. Demonstrates why cable sizing must account for the full load current including harmonic content.
Machine shop motors failing repeatedly despite no change in mechanical loads and other equipment on the same service working normally. Motor rewind shop supervisor used Fluke measurement to identify voltage unbalance plus harmonic distortion — classic combination that produces negative-sequence rotor currents, dramatically increasing motor winding temperature and shortening motor life.
Paper mill voltage sag costs $250,000 per event. A 5-cycle interruption at a glass plant costs $200,000 minimum. Duke Energy and Clemson University developed the Webstand portable process simulator to establish the immunity boundary — the voltage sag depth and duration at which the textile or film production process trips — before production losses occur rather than after.
A glass factory imported from a 60 Hz country to a 50 Hz country suffered repeated electronic control failures, reducing production capacity by 50%. Voltmeters and simple monitors failed to capture the cause. Full PQ monitoring eventually revealed voltage transients and harmonic distortion incompatible with the 60 Hz-designed electronics — a frequency migration problem compounded by poor power quality.
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.
