The core factors affecting transformer insulation performance include temperature, humidity, oil preservation methods, overvoltage, and short-circuit electromagnetic forces. These factors often interact and reinforce one another, collectively determining the aging rate and service life of the insulation.
The Vziman series oil-immersed on-load tap-changing power transformers have been systematically optimized in terms of materials, structure, and manufacturing processes to address the above factors, significantly retarding insulation aging and enhancing operational reliability.
1. Influence of Temperature
Transformers employ oil-paper composite insulation, and temperature directly affects the moisture equilibrium and migration between oil and paper, as well as the thermal degradation rate of cellulose. The higher the temperature, the more intense the ring-opening and chain-scission reactions of cellulose, with CO and CO₂ generation rising exponentially, substantially shortening insulation life. In the range of 80–140°C, the aging rate doubles for every 6–8°C increase in temperature rise.
【Vziman Countermeasure】 By employing high-efficiency oil-circulation cooling and optimized winding design, the hot-spot temperature rise of the windings is effectively reduced. Measured temperature-rise margins exceed standard requirements, fundamentally retarding thermal aging of the insulation and ensuring a design life of 20–30 years. This makes the transformers suitable for sustained high-load scenarios such as industrial parks and urban power grids.
2. Influence of Humidity
Moisture accelerates cellulose degradation, lowers the spark discharge voltage of oil, increases the dielectric dissipation factor (tanδ), catalyzes oil oxidation, and may lead to insulation breakdown in severe cases. However, the generation of CO and CO₂ is not determined solely by moisture content; it must be assessed in conjunction with temperature, the degree of oxygen participation, and operating history.
【Vziman Countermeasure】 The adoption of a fully sealed tank structure and high-quality sealing components effectively prevents external moisture ingress, significantly reducing the moisture content in the oil and maintaining high electrical strength of the oil-paper insulation. This ensures reliable operation even in environments with relative humidity up to 90% (at +25°C), making it particularly suitable for coastal, high-humidity, and polluted areas.
Vziman Sealed Oil-Immersed power Transformer
3. Influence of Oil Preservation Methods
Dissolved oxygen in the oil accelerates insulation oxidation, and its concentration depends on the oil preservation method. In open-type transformers, CO readily escapes, resulting in relatively low concentrations (100–500 ppm); in sealed transformers, CO and CO₂ accumulate effectively and may reach several thousand ppm. Therefore, insulation aging assessment must be differentiated based on the preservation method.
【Vziman Countermeasure】 Advanced sealed structures such as bladder-type or nitrogen-blanket protection are adopted to effectively isolate oxygen and inhibit oil oxidation. At the same time, CO and CO₂ are allowed to accumulate in the oil, enabling accurate aging trend tracking through DGA. This not only extends insulation life but also provides a reliable basis for condition-based maintenance.
4. Influence of Overvoltage
Transient overvoltages (phase-to-phase voltage rise of the non-faulted phase in an ungrounded neutral system), lightning overvoltages (steep wavefronts causing concentrated stress on inter-turn longitudinal insulation), and switching overvoltages (cumulative damage from repeated surges) have distinct degradation mechanisms.
Vziman S11 Series Oil-Immersed Sealed Power Transformer
【Vziman Countermeasure】 Strictly complying with IEC/GB standards, the winding structure is optimized to improve the initial voltage distribution under lightning overvoltage conditions. Ample main insulation margins ensure robust performance against transient overvoltages, guaranteeing safe operation under complex grid conditions.
5. Influence of Short-Circuit Electromagnetic Forces
Under outlet short-circuit conditions, enormous electromagnetic forces can cause winding deformation, lead displacement, and loosening of support members, altering insulation clearances and inducing localized overheating. Such damage is sudden and irreversible.
【Vziman Countermeasure】 The anti-short-circuit design is reinforced: windings adopt a high-mechanical-strength clamping structure with dual axial and radial supports, while the core and clamping fixtures are firmly secured. These measures effectively withstand short-circuit impacts, ensuring insulation integrity after sudden short circuits, and are especially suitable for industrial power supply applications with high short-circuit capacity.
Conclusion
The Vziman three-phase oil-immersed on-load tap-changing power transformer embodies systematic technical enhancements in thermal management, sealing and moisture protection, oil preservation, overvoltage withstand capability, and short-circuit resistance, synergistically mitigating insulation aging factors from multiple dimensions.
The Vziman three-phase oil-immersed on-load tap-changing transformer is systematically enhanced in thermal management, moisture sealing, oil preservation, overvoltage tolerance, and short-circuit resistance to jointly curb insulation aging. Its fully sealed outdoor design suits power projects below 1,000 m altitude, making it a reliable choice for modern grids.
Edited From：Echo
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