Transformer cable paper

Transformer cable paper (also known as transformer insulation paper) is a key insulation material inside transformers, mainly used to isolate live parts and grounding parts, conductors with different potentials, and assist in heat dissipation and structural fixation. Its core function revolves around insulation, heat dissipation, and structural protection. The specific functions and principles are as follows:

1、 Core function: Electrical insulation (the most critical function)

When a transformer is in operation, there is a high voltage inside (ranging from several thousand volts to several hundred thousand volts), and there is a significant potential difference between different windings and the iron core/oil tank. Direct contact can cause a short circuit, leading to equipment burning or even explosion. The core value of cable paper is to block current leakage through excellent insulation performance, which is specifically reflected in:

Isolate components with different potentials

Interwinding insulation: wound between high and low voltage windings to prevent the current of the high voltage winding from "breaking through" and leaking to the low voltage winding;

Winding to ground insulation: wrapped around the outside of the winding, isolating the winding from the grounded iron core and oil tank to prevent direct current from entering the ground;

Wire turn insulation: A very thin cable paper (such as 0.08-0.2mm thickness) is wrapped around a single enameled wire to prevent partial discharge or short circuit between adjacent wire turns due to potential difference.

Tolerate high electric field strength

The material of transformer cable paper is based on plant fibers (such as wood pulp) or synthetic fibers (such as aramid). After special treatment, its "breakdown field strength" (the critical electric field strength for insulation breakdown) can reach 15-25kV/mm (the air breakdown field strength is only about 3kV/mm), which can withstand high voltage in the narrow space inside the transformer and avoid insulation failure.

2、 Auxiliary function: heat dissipation and conduction

During the operation of transformers, the windings and iron cores generate a large amount of heat due to copper and iron losses. If heat accumulates, it can accelerate insulation aging, shorten equipment life, and even cause thermal breakdown. Cable paper plays the role of "heat conduction medium" in the heat dissipation system:

Collaboration with transformer oil: Cable paper is an oil absorbing material that can fully absorb transformer oil (the cooling medium inside the transformer), forming a "paper oil composite insulation system";

Accelerated heat transfer: The heat generated by the winding is first transferred to the cable paper, then conducted to the oil tank wall through the transformer oil in the paper, and finally released to the outside through the oil tank heat sink or cooler to avoid local overheating.

3、 Structural protection: fixation and buffering

During the operation of transformers, vibrations or deformations may occur due to electromagnetic forces (such as instantaneous impact forces during short circuits) and temperature changes (thermal expansion and contraction). Cable paper can provide structural support through its physical properties

Fixed winding shape: The cable paper wrapped around the outside of the winding can tightly bind the wire, prevent the winding from loosening or shifting during vibration, and ensure the regularity of the winding;

Buffer mechanical stress: Cable paper has a certain degree of flexibility and can absorb the electromagnetic impact force on the winding during a short circuit, reducing the risk of wire deformation or insulation damage;

Isolation of impurities and moisture: The dense structure of cable paper can prevent small impurities (such as metal debris and fiber dust) in transformer oil from adhering to the surface of the winding, while reducing the intrusion of external moisture (requiring sealing design) and avoiding a decrease in insulation performance.