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Every power transformer leaves the factory with its nameplate—voltage, capacity, impedance and temperature rise. For most manufacturers this signifies the end of their engineering efforts. At Jiangsu Ryan Electric, this is only the beginning. By integrating premium insulation materials with precision winding designs, honed through decades of Eaton joint venture experience, our power transformer units can be engineered with service lives more than 10 years over industry norms, which reduces capital expenditures, increases operating efficiencies, and improves the reliability for customers in more than 80 countries.
The Thermal Foundation: Insulation That Defies Aging
By far, the number one determining factor of a power transformer’s lifespan is the thermal aging of its insulation system. As soon as a unit starts operating, the cellulose-based insulation starts to degrade and it is estimated that every 6°C to 10°C over rated temperature effectively doubles the insulation’s aging rate. Jiangsu Ryan Electric overcomes this challenge through the application of premium insulation materials, characterized by a high tolerance to heat.
At the heart of our power transformer windings are thermally upgraded Kraft paper and-for more demanding applications, high-temperature materials that remain mechanically robust at temperatures that would cause conventional insulation to become brittle. As a result, these insulation systems possess a higher thermal class rating which extends the amount of time that normal operating temperatures can be maintained without rapid insulation aging. For liquid-immersed power transformers, natural and synthetic ester fluids are offered that provide excellent moisture tolerance and are less likely to age than conventional mineral oils. These thermally resistant power transformer designs offer the reliability to outlast competitive units by years.
Void-Free Construction Through Vacuum Pressure Impregnation
Most power transformer insulation failures originate is not within intact materials, but at boundaries between individual components. Tiny air voids become points of partial discharge—essentially mini-corona electrical stresses—that erode surrounding insulation until total failure occurs. Preventing these voids requires a manufacturing process that, while commonplace in some industries, many power transformer manufacturers simply cannot accomplish.
At Jiangsu Ryan Electric, all power transformer units are built using advanced vacuum pressure impregnation technology. First, all windings are placed under a deep vacuum, removing any traces of moisture that might be in the materials that could negatively impact dielectric strength. Next, the insulating resin is injected under vacuum ensuring that it penetrates the windings, filling every crevice. Finally, pressure is applied to force the resin even into the smallest of spaces, resulting in a fully void-free insulation system, removing all potential for partial discharge to occur. Each and every VPI power transformer that leaves our factory is tested for partial discharge in our CNAS accredited laboratories, verifying that our precision manufacturing techniques ensure long-life operation.
Precision Winding: Managing Mechanical and Electrical Stress
Of course,the two major failure modes are not only thermal. In order to meet the demands placed upon them from short circuits to sustained high voltages, our power transformer units are built using the most precise winding techniques that are employed in modern manufacturing-they serve to manage both mechanical and electrical stress on a power transformer's windings.
The windings are produced by maintaining a precisely uniform distance between each conductor throughout the winding process. This exact turn-to-turn spacing not only reduces the local electrical stress concentration t—which accelerates aging—but it also sets the stage for handling the high mechanical forces of a short circuit by providing the windings with consistent structural support. These precision windings are also built with transposed conductors which significantly reduce circulating current in multi-strand windings (an additional heat source). This all translates to longer lasting units as both electrical and mechanical stress are managed by this carefully orchestrated winding process.
Validating Longevity Through Rigorous Testing
Of course, materials and designs only go so far; the quality must be verified through careful and robust testing procedures. To do so, Jiangsu Ryan Electric uses dual 35kV and 110kV test bays equipped to perform all routine, type and special tests required for power transformer units. Our two test laboratories are CNAS accredited and, in addition to the aforementioned, can perform temperature rise tests at rated and accelerated loadings as well as the extremely important lightning impulse test that confirms the dielectric integrity of the insulation system during overvoltage events. Short-circuit withstand tests are performed to confirm the mechanical design of the windings under stress and are tested to greater than expected fault levels to ensure robustness. Every power transformer using our proprietary insulation materials and winding design undergoes each of these tests. This ensure the longevity we promise—verified in more than 50 countries throughout the world and trusted by leading entities ranging from renewable energy organizations to national electrical utilities.
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