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Home / 2019 issue 6 / DISTRIBUTION OF PARTICLES OF IMPURITIES ON ELECTRIC STRENGTH TRANSFORMER OIL INFLUENCES

DISTRIBUTION OF PARTICLES OF IMPURITIES ON ELECTRIC STRENGTH TRANSFORMER OIL INFLUENCES

O.S. Melnikova

Vestnik IGEU, 2019 issue 6

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Abstract in English: 

Abstract

 

Background: In order to extend the service life and ensure the operability of oil-filled transformer equipment in operation, much attention is paid to the development of methods for monitoring the state of their oil-barrier insulation. When monitoring the technical condition of transformer oil, the class of liquid purity is determined depending on the rated voltage of the equipment, however, the influence of the parameters of mechanical impurities on the breakdown voltage is not taken into account, thereby lowering the requirements for the quality of oil barrier insulation. In this regard, it is relevant to study the influence of the size distribution of impurity particles on the electric strength of the internal insulation of power transformers and determine the parameters of particles of mechanical impurities to justify the underestimation of the quality indicators of transformer oil in operation.

Materials and methods: Methods of mathematical statistics were used using the Gnedenko-Weibull distribution based on the standard values of liquid purity classes. To determine the maximum and minimum voltages, the standard values of the average breakdown voltages and the results of operational tests of transformer oil in a standard spark gap were used.

Results: The relationship between the particle size of mechanical impurities and the breakdown voltage of transformer oil is established. Based on the results of the study, a particle size distribution of impurities was obtained for 12 and 13 classes of liquid purity for power transformers with a voltage of 110-750 kV, a particle size range was determined that determines the maximum and minimum breakdown voltages, and the values of limit concentrations of mechanical particles were established.

Conclusions: The obtained parameters of impurity particles, which determine the maximum and minimum breakdown voltages of the operating oils, can be used to evaluate the technical condition when diagnosing the internal insulation of power transformers in order to increase their operational reliability, as well as to adjust the regulatory requirements for the quality of operational transformer oil according to the content of mechanical impurities.

 

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Key words in Russian: 
Ключевые слова: трансформатор, трансформаторное масло, пробивное напряжение, электрическая проч-ность, статистические характеристики, механические примеси, класс чистоты жидкости.
Key words in English: 
Keywords: transformer, transformer oil, breakdown voltage, electric strength, statistical characteristics, mechanical impurities, liquid purity class.
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