電圧が膨張する (1.1–1.8 pu, 0.5 サイクル 1 分) cause MOV failures, VFD 過電圧トリップ, 絶縁応力, 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.
A steel mill with variable speed drives experienced frequent VSD tripping with “ACライン過電圧” 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.
Belgian MV distribution network segment used to study the impact of distributed generation technologies (wind, PV, CHP) on power quality and voltage stability. Four cable feeders from a 14 MVA 70/10 kV transformer. Analysis shows how DG penetration affects voltage profiles, harmonic injection, and voltage stability — with practical implications for network planning with high DG penetration.
Over 90% of worldwide facilities operate at voltages higher than required — a consequence of distribution network design that delivers minimum voltage at the far end of the feeder. MicroPlanet’s voltage reduction technology captures wasted energy by operating equipment at optimal voltage, reducing heat losses in electronic components without affecting performance.
Solar PV power conditioners maintain output by monitoring grid voltage and frequency — but malfunction when grid voltage rises above threshold or frequency deviates. Problems include inverter trips, inability to sell back power due to overvoltage, and high-order harmonic injection from neighbouring PV systems. Field measurement identifies the dominant disturbance type.
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 Vrmsの. Supply quality was far outside acceptable limits during off-peak hours.
A factory 200V three-phase circuit recorded recurring transient overvoltages on all three phases simultaneously — occurring twice per fundamental cycle with 820 µs spacing, 間で 10 kHzと 30 kHzの, 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.
Glow fluorescent lighting generates transient overvoltage when the glow lamp initiates the warm-up sequence — a known but frequently overlooked phenomenon. The transient occurs at first ignition and can affect nearby electronic equipment connected to the same circuit. Measurement shows the waveform characteristics and suggests threshold settings for event detection.
Rural transformer failure at the end of a medium-voltage feeder serving an apartment complex, dairy farm, and golf course. Fluke investigation found the transformer failed from sustained overloading combined with harmonic current from a variable-speed pump at the dairy farm. Demonstrates that harmonics contribute to transformer failure through additional winding losses — even in rural settings with “clean” loads.
