With the upgrading of power systems and the increasing demand for new energy equipment, the performance requirements for transformer insulation materials are constantly improving. Among various insulation materials, heat-resistant DDP insulation paper (Dotted Diamond Paper), with its excellent heat resistance, mechanical strength, and oil impregnation performance, has become an important insulation component inside oil-immersed transformers. This article will explain in detail the key role of heat-resistant DDP insulation paper in transformer manufacturing from the aspects of material characteristics, application locations, advantages of use, and industry trends.
Heat-resistant DDP insulation paper is made by coating the surface of electrical cellulose insulation paper with thermosetting epoxy resin in a diamond-shaped dot pattern. Its structure determines the following properties:
1. High heat resistance
2. Good adhesion
3. Excellent dielectric properties
4. Strong adaptability
Heat-resistant DDP insulation paper is commonly used inside the windings (such as turn-to-turn and layer-to-layer insulation), as well as between the windings and the core or other structural components. It provides reliable electrical isolation, preventing transformer short circuits and leakage.
Its dense fiber structure and thermal resistance ensure insulation stability under high electric fields. It can withstand transient overvoltages that occur during transformer operation.
Heat-resistant DDP insulation paper is typically made from high-temperature materials such as aramid fibers (e.g., Nomex®). Its long-term thermal endurance can exceed 150°C, with even higher short-term temperature resistance. This allows transformers to operate at higher temperatures, thereby increasing overload capacity or extending service life.
Even in high-temperature environments, the insulation paper maintains its mechanical and electrical properties, slowing down the degradation caused by thermal aging.
DDP insulation paper provides a certain level of mechanical toughness, offering support during winding and pressing processes to prevent conductor deformation or displacement.
It also enhances the durability of the windings under electromagnetic vibration, thermal expansion, and contraction.
In terms of oil resistance and corrosion resistance, DDP insulation paper is not easily degraded in transformer oil or other cooling media, and can resist impurities or oxidation products in the oil.
Its low hygroscopicity provides moisture and contamination resistance, reducing the decline of insulation performance caused by humidity.
Heat-resistant DDP insulation paper is widely used in several key transformer components and is an essential material for ensuring equipment reliability:
DDP insulation paper is used as spacing material between layers of high-voltage and low-voltage windings. It ensures proper electrical clearance and helps prevent partial discharge.
DDP insulation paper prevents turn-to-turn breakdown within transformer coils, maintaining stable electrical insulation even under high-load operating conditions.
After curing, the resin forms a strong supporting structure, ensuring minimal deformation of the windings during transportation, short-circuit events, and other mechanical stresses.
Heat-resistant DDP insulation paper is suitable for most oil-immersed transformers, including:
♦ 10 kV / 35 kV distribution transformers
♦ Energy-related transformers (energy storage systems, charging station PCS units)
♦ Industrial rectifier transformers
♦ Electric furnace transformers
♦ Amorphous core transformers
♦ Transformers used in power electronics equipment
Heat-resistant DDP insulation paper—thanks to its excellent electrical insulation, thermal resistance, mechanical strength, and chemical stability—effectively increases the operating temperature limit, overload capacity, safety, and service life of transformers. It is a key material in modern high-efficiency and compact transformer designs.
When selecting heat-resistant DDP insulation paper, it is important to consider factors such as transformer type, insulation class, and operating environment.
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