The Global Oil Duct Struct Market was valued at USD 71.50 Million in 2025 and is projected to reach USD 119 Million by 2034, growing at a Compound Annual Growth Rate (CAGR) of 7.7% during the forecast period (2024–2034). This robust growth is being driven by massive global investments in grid modernization, the rapid integration of renewable energy sources, and increasing electricity demand from industrial electrification and urbanization trends.

As the power industry intensifies its focus on reliability, efficiency, and sustainability, the spotlight turns to the specialized manufacturers of oil duct structs—the critical spacer strips that ensure the thermal and dielectric integrity of power transformers. In this blog, we profile the Top 10 Companies in the Oil Duct Struct Industry—a mix of global insulation giants, precision component specialists, and regional leaders shaping the future of transformer performance.

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🔟 1. Hitachi Energy

Headquarters: Zurich, Switzerland / Västerås, Sweden
Key Offering: Axial Strips, Radial Spacer Strips, Precision-Machined Insulation Components

Hitachi Energy is a global powerhouse in power grid technology and a leading supplier of high-performance transformer insulation components. Their extensive portfolio includes a wide range of oil duct structs manufactured from high-density cellulose pressboard, engineered to meet the exacting standards of large power and distribution transformers. The company leverages deep transformer design expertise to provide customized spacer solutions.

Innovation and Quality Initiatives:

• Advanced machining for superior dimensional accuracy and edge quality

• Investment in R&D for next-generation materials with enhanced thermal and mechanical properties

• Global supply chain ensuring consistent quality and timely delivery for transformer OEMs worldwide

Download FREE Sample Report: Oil Duct Struct Market – View in Detailed Research Report

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9️⃣ 2. Weidmann Electrical Technology

Headquarters: Rapperswil-Jona, Switzerland
Key Offering: Weidmann Pressboard Strips, Custom Spacer Kits, High-Density Components

Weidmann Electrical Technology is a world-renowned leader in electrical insulation systems, with a storied history spanning over 140 years. The company is a top-tier supplier of oil duct structs, known for its vertically integrated manufacturing process that controls quality from raw pulp to the final precision-machined component. Their products are specified by leading transformer manufacturers for critical applications.

Innovation and Quality Initiatives:

• Pioneering development of pre-compressed and thermally upgraded pressboard for superior dimensional stability

• Global technical service and support teams working closely with customers on transformer design optimization

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8️⃣ 3. KREMPEL Group

Headquarters: Heilbronn, Germany
Key Offering: Transformer Board Strips, Calibrated Spacer Strips, Laminated Components

The KREMPEL Group is a major European player specializing in high-quality electrical insulation materials. Their product range for the transformer industry includes a comprehensive selection of oil duct spacer strips, known for their precision and reliability. KREMPEL serves a global clientele with a strong focus on innovation and material science.

Innovation and Quality Initiatives:

• Development of specialized pressboard grades for demanding applications like HVDC transformers

• Emphasis on sustainable manufacturing practices and material traceability

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7️⃣ 4. Nantong Zhongling Electric Power Technology Co., Ltd.

Headquarters: Nantong, Jiangsu, China
Key Offering: Axial Strips, Radial Spacers, Transformer Insulation Components

Nantong Zhongling is a key Chinese manufacturer of insulation components for the power industry. The company has established itself as a significant supplier within Asia’s booming transformer market, providing cost-effective and reliable oil duct structs to both domestic and international OEMs. Their growth is supported by China’s massive investments in power infrastructure.

Innovation and Quality Initiatives:

• Expansion of production capacity to meet rising demand from grid expansion projects

• Investment in advanced machining technology to improve product precision and consistency

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6️⃣ 5. Henan YAAN Electrical Insulation Plant

Headquarters: Xinyang, Henan, China
Key Offering: Insulation Pressboard Strips, Dovetail and T-Strips, Custom Components

Henan YAAN is a specialized manufacturer of electrical insulation materials with a strong presence in the Chinese market. The company produces a variety of oil duct struct profiles, including complex shapes required for advanced transformer designs. They are known for their responsiveness and ability to serve the high-volume demands of the regional transformer industry.

Innovation and Quality Initiatives:

• Focus on manufacturing a wide range of profiles to cater to diverse transformer specifications

• Continuous improvement in quality control processes to meet international standards

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5️⃣ 6. Shandong Jinbao Electrical Insulation Materials Co., Ltd.

Headquarters: Weifang, Shandong, China
Key Offering: Transformer Spacer Strips, Insulation Laminates, Presspaper Components

Shandong Jinbao is another prominent Chinese supplier contributing significantly to the oil duct struct market. The company manufactures insulation components used in various types of oil-immersed transformers. Their competitive positioning is strengthened by China’s role as a global manufacturing hub for power equipment.

Innovation and Quality Initiatives:

• Adoption of automated manufacturing lines to enhance production efficiency

• Development of products tailored for the renewable energy and traction transformer sectors

Download FREE Sample Report: Oil Duct Struct Market – View in Detailed Research Report

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4️⃣ 7. Shenyang Defeng Insulation Material Co., Ltd.

Headquarters: Shenyang, Liaoning, China
Key Offering: Insulation Strips, Pressboard Components, Transformer Spacers

Shenyang Defeng is a recognized manufacturer of insulation materials in Northeast China. The company supplies oil duct structs to transformer builders across the country, benefiting from the region’s industrial base. They focus on producing reliable components that meet the practical needs of the power transmission and distribution sector.

Innovation and Quality Initiatives:

• Strengthening supply chain partnerships with domestic transformer OEMs

• Focus on cost-competitive manufacturing while maintaining essential quality parameters

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3️⃣ 8. Von Roll Holding Ltd.

Headquarters: Zurich, Switzerland
Key Offering: High-Performance Insulation Strips, VPI-Compatible Components

Von Roll is a global leader in electrical insulation with a comprehensive product portfolio that includes solutions for power transformers. While competing in a crowded field, the company is known for its technological expertise and high-quality materials. Their oil duct structs are used in demanding applications where performance and reliability are paramount.

Innovation and Quality Initiatives:

• Research into novel insulation materials and systems for future grid challenges

• Providing integrated insulation solutions that include other components like barriers and cylinders

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2️⃣ 9. Isovolta AG

Headquarters: Werndorf, Austria
Key Offering: Laminated Pressboard Strips, Composite Insulation Components

Isovolta, part of the Schweitzer Industries group, is a well-established European manufacturer of composite materials and insulation products. The company produces high-quality pressboard-based strips and other components for the electrical industry. Their technical expertise allows them to serve niche and high-performance segments of the transformer market.

Innovation and Quality Initiatives:

• Specialization in laminated and composite materials for enhanced mechanical and dielectric properties

• Focus on customized solutions for specific customer and application requirements

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1️⃣ 10. 3M Company (Electrical Markets Division)

Headquarters: Saint Paul, Minnesota, USA
Key Offering: Advanced Composite Strips, Dielectric Materials, High-Temperature Components

3M’s Electrical Markets Division is a global innovator in materials science, offering a range of products for electrical applications. While not a traditional pressboard supplier, 3M competes in the high-value segment with advanced composite materials that can serve as alternatives or complements to cellulose-based oil duct structs in certain transformer designs, particularly where higher thermal performance is needed.

Innovation and Quality Initiatives:

• Pioneering research into non-cellulosic dielectric materials with superior properties

• Focus on enabling transformer designs with higher power density and improved efficiency

Get Full Report Here: Oil Duct Struct Market – View in Detailed Research Report

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🔩 Outlook: The Future of Oil Duct Structs Is Precision and Performance

The oil duct struct market is undergoing a significant evolution. While traditional pressboard strips remain the workhorse of the industry, the focus is shifting towards components that enable higher transformer efficiency, reliability, and power density. Manufacturers are investing in precision engineering and advanced materials to meet the stringent demands of modern grid infrastructure.

📈 Key Trends Shaping the Market:

• Transition from basic material supply to value-added, precision-machined component kits

• Growing demand for higher-density and pre-compressed materials for superior dimensional stability

• Increased emphasis on supply chain reliability, quality traceability, and technical partnership with transformer OEMs

• R&D into nanocellulose and composite materials to push the boundaries of thermal and dielectric performance

Get Full Report Here: Oil Duct Struct Market – View in Detailed Research Report

The companies listed above are not only supplying critical components—they are enabling the reliability and efficiency of the global power grid.