Application of DDP Insulation Paper in Oil-Immersed Transformer Windings

Oil-immersed transformers are core equipment in power systems, and the selection of insulation materials directly affects their operational reliability, efficiency, and safety. DDP insulation paper is a high-performance solid insulation material that plays a crucial role in the insulation structure of transformer windings. This article will describe the characteristics of DDP insulation paper, its specific applications in oil-immersed transformer windings, and its corresponding technical advantages.

Overview of DDP Insulation Paper

DDP insulation paper is a high-density, high-purity cellulose insulation paper. It is manufactured using a special double-density pressing process, resulting in higher mechanical strength and electrical properties. Compared to ordinary insulation paper, DDP insulation paper typically has a density exceeding 1.15 g/cm³, lower porosity, and a denser fiber structure, maintaining stable performance in an oil-immersed environment.

Performance Advantages of DDP Insulation Paper:

Excellent electrical properties

Outstanding mechanical properties

Good thermal aging performance

Good compatibility with transformer oil

The Core Role of DDP Insulating Paper in Oil-Immersed Transformer Windings

1.Inter-layer and Inter-turn Insulation

Reliable electrical isolation structures are required between the winding conductors of oil-immersed transformers. DDP insulating paper, with its high dielectric strength, effectively prevents inter-turn breakdown and partial discharge, improving the safety margin of winding insulation.

2.Winding Structure Fixation and Enhanced Short-Circuit Resistance

During the drying and hot-pressing process of the windings, the resin dots on the surface of the DDP insulating paper melt and bond to the conductors, forming a unified winding structure. The specific functions are as follows:

Improve the axial and radial mechanical strength of the windings

Enhance the windings' resistance to deformation under short-circuit impacts

Reduce the risk of winding loosening during transportation and operation

This role is particularly important for medium- and high-voltage oil-immersed transformers.

3. Improved Stability

DDP insulating paper has good compatibility with transformer oil. During long-term operation in transformer oil, DDP does not experience resin shedding or performance degradation, maintaining the stability of the oil-paper insulation system.

Application Scenarios of DDP Insulation Paper in Different Types of Oil-Immersed Transformers

1. Distribution Transformers (10kV/11kV/20kV/35kV)

DDP insulation paper is used for turn-to-turn and inter-layer insulation of the low-voltage and high-voltage windings of this type of transformer, improving the performance consistency and operational reliability of the finished transformer.

2. Medium-Voltage and High-Voltage Oil-Immersed Power Transformers

In products with voltage levels of 110kV and below, DDP insulation paper is widely used in the fixed insulation structure of copper or aluminum conductor windings, meeting the higher requirements of equipment for short-circuit strength.

3. Oil-Immersed Transformers in Special Application Scenarios  (New Energy Support, Export Type)

Oil-immersed transformers exported to Africa, the Middle East, Southeast Asia and other regions can enhance their adaptability to high-temperature and high-humidity operating environments by using DDP insulating paper.

Key Selection Considerations for DDP Insulation Paper for Oil-Immersed Transformer Windings

In practical selection, the following factors should be given special attention:

♦ Base paper thickness and basis weight – match the winding structure

♦ Resin type and coating density – directly affect bonding strength

♦ Heat resistance rating – comply with relevant transformer design standards

♦ Product certification – meet international and national standards such as IEC, GB, and UL

Proper selection of DDP insulation paper can improve the overall performance of the transformer and reduce the incidence of after-sales failures.

Application Precautions for DDP Insulation Paper

Drying Treatment: Before assembly, the DDP insulation paper must be thoroughly dried to remove internal moisture.

Vacuum Impregnation: Employ a thorough vacuum impregnation process to ensure the insulating oil fully penetrates the DDP insulation paper.

Quality Control: Strictly test the thickness, density, and moisture content of the DDP insulation paper.

Design Optimization: Select DDP insulation paper of appropriate thickness based on the winding electric field distribution.

DDP insulation paper is a key insulation material for oil-immersed transformer windings. Its excellent electrical properties, mechanical strength, and thermal stability improve the reliability and service life of transformers. With upgrades in manufacturing processes and the accumulation of application experience, DDP insulation paper will continue to play a vital role in the insulation of power equipment, ensuring the stable operation of the power grid.

Transformer manufacturers, power companies, and maintenance service providers must understand the characteristics of DDP insulation paper and apply it correctly. This is a key technical measure to ensure the long-term reliable operation of transformers and reduce the total life-cycle cost of equipment.

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