porcelain insulators
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The surface discharge development processes of polluted porcelain insulators for power transmission lines are tightly related with the development of leakage current (LC), the characteristics of LC, the insulating condition, and discharge intensity of the insulator surface have an important significance for revealing the contamination discharge state of insulators. In order to analyze the LC characteristics of porcelain insulators in the process of pollution flashover, artificial pollution flashover tests on porcelain insulators were conducted in the artificial fog cabinet, and the characteristics of LC waveforms in time-domain and frequency-domain were simultaneously measured and analyzed during the tests. The results indicated that the amplitude of LC, fundamental harmonic, the third harmonic, and fifth harmonic had a strong correlation, the maximum of LC(Im), the rate of total harmonics (THD), and the phase difference of fundamental harmonic (θ) were used for the representation of the characteristics of the LC waveform. The LC has the characteristics of high amplitude, low proportion harmonic, and small phase difference between the fundamental harmonic and voltage before the flashover occurrence. The test results provide effective reference for porcelain insulators in pollution flashover forecasting.

This article is dedicated to an important problem of increasing the reliability of supporting-rod porcelain insulation at electric power substations. Porcelain insulation is installed on open switchgears (OSGs) of substations as part of the main switching equipment. Obsolescence and physical wear results in the destruction of supporting-rod porcelain insulators (SRIs), which often leads to serious consequences: shutdown of substation bus systems, emergency shutdown of substation equipment, reduction of power plant loads, as well as they pose a threat to operational personnel during operational switching. When supporting-rod insulation is replaced in due time, it significantly increases the reliability of the main substation equipment. Possible causes of failures were analysed using a graphical technique (Ishikawa diagrams). It has been established that sudden temperature changes of the ambient air are an important negative aspect, especially the transition of temperature values through 0ºC. The work represents a mathematical model of the development of microfractures in the insulation body of a ceramic insulator. The influence of external forces on the insulator leads to the appearance of additional stresses in it, to the destruction of new particles and to the sudden growth of microfractures. The article gives main SRI diagnostic techniques currently used in the electric power industry. According to statistics, it has been established that a relevant approach is the transition to digital technologies, which provides an automated information processing process without deactivating a piece of equipment. The article describes and proves that the proposed system of diagnostics of supporting-rod porcelain insulation at digital substations without deactivating a piece of equipment is a relevant area of scientific development. Within the framework of this scientific study, a patent for invention No. 2743887 dated 20 April 2020 was obtained.

This paper reviewed the production of electric porcelain insulators utilizing from local raw materials from developing countries. The raw materials used were feldspar, quartz/silica and kaolin. The chemical composition, mineralogy, and thermal properties of the raw materials were characterized using AAS, XRD, and TGA respectively. Different weight percentage combinations of the individual raw materials were investigated by the authors. Most of the results showed relatively acceptable porcelain insulators properties such as low water absorption, porosity, high insulation resistance, dielectric strength and bulk density. The paper showed that electric porcelain insulators with good properties can be produced from available local raw materials in some developing countries using appropriate formulations. However, for production of improved porcelain insulators properties, suggestions were made on the areas for future research.