Effect of Radial Moisture Distribution on Frequency Domain Dielectric Response of Oil-Polymer Insulation Bushing.

Daning Zhang,Yang Li,Guanjun Zhang,Guanwei Long,Haibao Mu

doi:10.3390/polym12061219

Abstract

In order to realize the diagnosis of water distribution, this paper analyzes the interface polarization and macroscopic space charge polarization mechanism when the water distribution is non-uniform. The experimental results of this paper and bushing show that when the moisture distribution is non-uniform, there is a significant loss peak in the tanδ-f curve. The loss peak shifts to higher frequencies as the non-uniformity coefficient increases. There are common intersection points between multiple tanδ-f curves. Further, this paper realizes the diagnosis of the location of moisture distribution through Frequency Domain Spectroscopy (FDS) testing of different voltages and different wiring methods based on the macroscopic space charge polarization. In the single-cycle FDS test, when the positive electrode is first added to the area with higher moisture content, the amplitude of the tanδ-f curve is smaller. The tanδ-f curves under different wiring methods constitute a “ring-shaped” loss peak. As the voltage increases, the peak value of the loss peak shifts to the lower frequency band. As the temperature increases, the peak value of the loss peak shifts to higher frequencies. Based on the above rules and mechanism analysis, this research provides a new solution for the evaluation of moisture content of oil-immersed polymers equipment.

Highlights

As an important part of the external insulation of transformers, high-voltage oil-immersed polymer insulation bushings are characterized by large quantities, high prices, and excellent insulation properties.the scientific and effective diagnostic evaluation of its insulation status determines the safety and stability of the high-voltage power grid
This paper proposes a method of radial dampness assessment based on interface polarization and macroscopic space charge polarization in Frequency Domain Spectroscopy (FDS)
When the moisture content of oil-polymer sample is large, the increase of water makes the of ions dissociated by water molecules increase, and at the same time, water as an ideal solvent number of ions dissociated by water molecules increase, and at the same time, water as an ideal for weak electrolytes makes the degree of dissociation of impurity molecules increase

Summary

Introduction

As an important part of the external insulation of transformers, high-voltage oil-immersed polymer insulation bushings are characterized by large quantities, high prices, and excellent insulation properties.the scientific and effective diagnostic evaluation of its insulation status determines the safety and stability of the high-voltage power grid. As an important part of the external insulation of transformers, high-voltage oil-immersed polymer insulation bushings are characterized by large quantities, high prices, and excellent insulation properties. Moisture of the bushing is one of the main causes of its insulation failure. The accumulation of moisture in the insulation polymer significantly increases the partial discharge; and the breakdown field strength is greatly reduced, which in turn causes electrical accidents [2]. Due to the capacitive plate structure of the bushing, external water intrusion and incomplete initial drying will lead to non-uniform moisture distribution in the bushing. Local high moisture content (mc) can lead to accelerated thermal aging of the polymer [3]. It is necessary to diagnose the local moisture content of the bushing. Clarifying the relative position of high moisture in the capacitive screen will improve product design

Results

Discussion

Conclusion