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DDP Insulation Paper (Diamond Dotted Paper), also known as Diamond Dotted Insulation Paper or Diamond Pattern Dotted Paper, is a functional electrical insulation material specially designed for transformer winding insulation and interlayer bonding.
DDP uses high-performance electrical insulating paper as the base material. Through a specialized dot-coating process, a thermosetting adhesive is applied to the surface of the paper in a regular diamond-shaped pattern. During the transformer winding manufacturing process, the adhesive dots are activated and cured under controlled heating and pressure, bonding the insulation paper to adjacent insulation layers.
Therefore, DDP combines the functions of electrical insulation, interlayer bonding, and mechanical reinforcement of transformer windings.
DDP is mainly used in oil-immersed power transformers, distribution transformers, reactors, and other electrical winding equipment.
DDP stands for Diamond Dotted Paper.
Its basic structure consists of:
Electrical Insulation Paper Substrate + Diamond-Pattern Thermosetting Adhesive
Compared with conventional transformer insulation paper, the most distinctive feature of DDP is the presence of regularly distributed adhesive dots on its surface.
These adhesive dots are normally arranged in a specific diamond-shaped pattern. Under normal storage, transportation, and processing conditions, DDP can be handled similarly to conventional insulation paper. During transformer winding production, when exposed to specified heat and pressure, the adhesive softens, flows, and eventually cures.
As a result, DDP not only provides electrical insulation but also bonds different layers of the transformer winding together.
DDP can be placed between different layers of transformer windings to provide reliable electrical insulation between conductors at different electrical potentials.
Its main functions include:
Therefore, DDP is an important component of the insulation system used in transformer windings.
Interlayer bonding is one of the key features that distinguishes DDP from conventional insulation paper.
When heated under controlled conditions, the adhesive dots on the surface of DDP become activated and provide bonding between adjacent insulation layers and winding components.
In simple terms:
Conventional Insulation Paper: Mainly provides electrical insulation
DDP: Provides both electrical insulation and bonding
During a transformer short circuit, the windings can be subjected to significant electromagnetic forces.
If the winding layers are not sufficiently bonded, the following problems may occur:
Interlayer movement → Winding deformation → Insulation damage
After curing, DDP can improve the overall structural stability of the winding assembly, helping to enhance its mechanical strength and resistance to short-circuit forces.
DDP is most commonly used in oil-immersed transformers.
Typical applications include:
DDP is particularly suitable for winding structures that require interlayer bonding and mechanical reinforcement.
The core manufacturing process of DDP is the precise application of adhesive onto the surface of electrical insulation paper in a specified diamond-shaped pattern.
A typical DDP manufacturing process can be summarized as follows:
Electrical Insulation Paper Substrate → Base Paper Inspection → Unwinding → Adhesive Preparation → Diamond Dot Coating → Drying / Pre-Curing → Cooling → Slitting → Rewinding → Final Inspection → Packaging
High-quality electrical insulation paper is selected as the substrate. The base paper is inspected for thickness, surface quality, mechanical properties, and other relevant parameters.
The insulation paper is continuously unwound from the parent roll and fed into the coating system at a controlled speed and tension.
A suitable thermosetting adhesive is prepared according to the required performance and processing conditions of the DDP product.
The adhesive is precisely applied to the surface of the insulation paper in a regular diamond-shaped dot pattern. The coating amount, dot size, spacing, and distribution need to be carefully controlled.
The coated paper passes through a controlled drying or pre-curing process to remove solvents or moisture and achieve the required adhesive condition.
The DDP is cooled under controlled conditions to stabilize the adhesive coating and facilitate subsequent processing.
The material is slit into the required widths and rewound into rolls according to customer specifications.
The finished DDP is inspected for key parameters such as:
After passing final inspection, the DDP insulation paper is properly packaged to protect it from moisture, contamination, and mechanical damage during storage and transportation.
Compared with conventional insulation paper, DDP provides an additional bonding function while maintaining the basic electrical insulation properties required for transformer windings.
Its key advantages include:
The specific performance of DDP depends on the base insulation paper, adhesive system, coating pattern, adhesive content, thickness, curing conditions, and transformer design requirements.
If you are looking for DDP insulation paper for transformers, please contact ZTelec Group.
ZTelec Group is a professional manufacturer of high-quality electrical insulation materials with more than 65 years of manufacturing experience. We can provide DDP insulation paper according to your required specifications, thickness, adhesive pattern, roll width, and application requirements.
We can also provide technical data and samples for testing before bulk production.
Contact us today to obtain detailed product information, technical specifications, and a quotation.
