Insulation Types of Transformer Partial Discharge Investigation

1. The harm of transformer partial discharge

Transformer is an important equipment in the power system, and its normal operation is of great significance to the safe and reliable operation of the power system. However, during the operation of the transformer, partial discharge will occur. Partial discharge will cause the decomposition of insulating oil, gas generation, cause dielectric fracture, and eventually lead to transformer accidents. Therefore, it is very important to investigate the partial discharge of transformers.

2. Factors Affecting Partial Discharge

The occurrence and development of partial discharge are related to many factors, including voltage gradient, medium conductivity, electric field strength and so on. The selection and quality of insulating materials are also one of the important factors affecting partial discharge.

3. Insulation types that need to be considered in the investigation of partial discharge

3.1. Oil paper insulation

Oil-paper insulation is one of the most widely used insulating materials at present, and it has good insulation performance and heat resistance. In the inspection of transformer partial discharge, oil-paper insulation is also one of the main inspection objects. By detecting the physical and chemical indicators of insulating oil such as dissolved gas, humidity and acid value in the oil, it can be judged whether there is a problem with oil-paper insulation. However, the disadvantage of oil-paper insulation is that it will produce secondary pollution during operation, and it is also susceptible to moisture and heat, which affects the service life.

3.2. Air insulation

Air insulation is a simple and intuitive partial discharge test method. Its principle is to increase the voltage in the insulation system to make the partial voltage exceed the partial discharge inception voltage, thereby generating partial discharge. Although this method is simple and feasible, it is rarely used widely because air insulation has high requirements on environmental conditions and is susceptible to interference.

3.3. Composite insulation

Composite insulation is composed of different types of insulating materials, and by overcoming the shortcomings of various insulating materials, the purpose of optimizing insulation performance is achieved. Composite insulation is usually made of multiple insulating materials alternately laminated, including but not limited to oil-paper insulation, fiberboard insulation, epoxy cast insulation, etc., and has good insulation and mechanical properties. In the investigation of partial discharge, composite insulation is more and more widely used, but due to its high manufacturing cost, it is still being gradually promoted and applied.

4. Summary

The inspection of transformer partial discharge is an important part of transformer maintenance. Different insulating materials have different meanings and functions for the inspection of partial discharge. Oil-paper insulation, air insulation and composite insulation are all insulation types that need to be considered in the investigation of transformer partial discharge, and they each have their own advantages and disadvantages. It is necessary to select the appropriate insulation material according to the specific situation. In order to ensure the safe and stable operation of transformers, it is of great practical significance to investigate partial discharge.

HZ-9003C Multifunctional Partial Discharge Tester