C1100 Copper Strip for Oil-Immersed Transformers
2026-10-21
As core components in power transmission and distribution networks, the windings of oil-immersed transformers remain submerged for long periods in insulating oil at temperatures ranging from 80°C to 105°C. The purity and stability of the conductive material directly influence the lifespan of the insulating oil and the overall operational reliability of the transformer. Haomei Aluminum offers C1100 copper strips—corresponding to the C11000 electrolytic tough-pitch copper grade under the ASTM B152 standard—specifically optimized for oil-immersed environments, providing a stable winding material solution for high-capacity power transformers.
The advantage of the C1100 copper strip in oil-immersed environment lies in its high-purity composition. The total copper and silver content is no less than 99.90%, with oxygen content strictly controlled between 0.02% and 0.04%. Furthermore, the presence of harmful impurities—such as bismuth, antimony, arsenic, and lead—is strictly limited. This high-purity substrate effectively minimizes the precipitation of impurities at grain boundaries under high-temperature conditions, preventing an increase in the acid value of the insulating oil and a decline in its dielectric strength. This slows the aging process of the oil and extends the maintenance intervals for the transformer. Based on extensive export experience, it has been observed that in transformers in operation for over five years, the use of standard industrial-grade copper strips often accelerates the degradation of insulating oil due to the precipitation of impurities. In contrast, C1100-grade copper can reduce the rate of oil degradation by more than 40%, significantly enhancing the economic efficiency of the transformer over its entire lifecycle.
Regarding electrical conductivity, C1100 copper strips maintain a stable conductivity of 100%–101% IACS at room temperature, with a resistivity as low as approximately 0.0172 Ω·mm²/m. For a given current-carrying capacity, the lower DC resistance directly reduces Joule heating losses in the windings, enabling transformers to achieve S13, S15, or even higher energy-efficiency ratings. Furthermore, the uniform material microstructure ensures even current distribution and minimizes localized "hot spots." This, combined with the convective cooling provided by the insulating oil, ensures thermal stability for large-capacity transformers operating at full load over long periods.
To accommodate the specific requirements of oil-immersed transformer manufacturing—which involves winding wide strips under high tension—our copper strips undergo bright annealing in a protective atmosphere to achieve a stable, fully soft (O-temper) state. The finished strips feature a Vickers hardness (HV) controlled between 55 and 65, with a deviation of no more than 5 HV across the entire width, and an elongation at break of ≥35%. This mechanical uniformity ensures consistent stress distribution during high-tension winding, resulting in tight, gap-free contact between turns and a high winding fill factor. Additionally, the complete elimination of internal residual stress prevents winding displacement or insulation deformation—issues that could otherwise arise from stress release during long-term operation—thereby reducing the risk of mid-term equipment failure.
In terms of dimensional and surface specifications, C1100 copper strips are available in thicknesses ranging from 0.1 mm to 3.0 mm, with widths customizable to specific winding designs. We maintain a thickness tolerance within ±0.005 mm and a lateral straightness of ≤1 mm/m. The edges of the copper strip can be precision-rounded to eliminate burrs and sharp corners from the slitting process, thereby suppressing partial discharge between layers. The surface undergoes rigorous multi-stage cleaning to ensure the complete removal of rolling oils and oxidation marks. The material exhibits excellent compatibility with both mineral insulating oils and synthetic ester oils, posing no risk of inducing oil degradation or the formation of sludge.
The C1100 copper strip supplied by Haomei Aluminum complies with the international standard ASTM B152. Each shipment includes comprehensive material certification and performance test reports. We offer customized, large-coil-weight supply options, which help minimize the number of intermediate joints in windings and reduce the risk of welding defects. Haomei copper strip products are widely used in oil-immersed power transformers, distribution transformers, and reactors across voltage classes ranging from 10 kV to 500 kV. We provide tailored material selection advice and technical support to meet specific customer requirements. Please contact us for detailed specifications and price quotes.