Test method for assessing transformer oil breakdown voltage in high-voltage DC electric filed

Abstract

The invention discloses a test method for assessing transformer oil breakdown voltage in a high-voltage DC electric filed, and belongs to the technical field of power grid transmission and transformation. In the high-voltage DC electric filed, a cup for a ball-type electrode or a cup for a flat plate-type electrode is adopted, high voltage is connected into a pin-type electrode end, a ground line is connected into the ball-type electrode or a flat plate-type end, positive polarity DC voltage and negative polarity DC voltage are respectively adopted, and boosting is carried out according to a fixed rate. When breakdown happens to the transformer oil, boosting is stopped and the voltage value at the time is recorded, test is repeated for multiple times, and the average value of multiple test results serves as the breakdown voltage of the transformer oil. As the cup for a ball-type electrode or the cup for a flat plate-type electrode is adopted during the test process, an electrode type with an uneven electric field can be formed, the electrode structure can reflect polarity effect features of the electric field in the DC electric filed, the components and polarity effect correlation of the converter transformer oil can also be detected.

Description

technical field [0001] The invention relates to a test method for evaluating the breakdown voltage of transformer oil under a high-voltage direct current electric field, and belongs to the technical field of power grid transmission and transformation. Background technique [0002] In recent years, my country's power industry has entered the development period of large power grids and UHV power grids, and has successively built ±500kV HVDC and ±660kV and ±800kV UHVDC transmission projects. Converter transformers are extremely important power transmission and transformation equipment in DC transmission projects, and their industry development is closely related to the overall development of the UHV DC power grid industry. With the improvement of the voltage level of HVDC transmission projects in China, the voltage and capacity of domestic converter transformers have been greatly improved. The problem of internal insulation of converter transformers is becoming more and more p...

AI Technical Summary

Problems solved by technology

When the above methods are used to evaluate the insulation performance of transformer oil used in converter transformers, the biggest defect is that the test electric field is AC, not DC, which is quite different from the operating conditions of converter transformers, and the impact of the type of electric field on the breakdown voltage is not considered. The evaluation results are difficult to reflect the insulation characteristics of converter transformer oil under DC voltage

In addition, the electrodes used in the test are all symmetrical types, and mainly form a uniform or quasi-uniform electric field. This type of electrode cannot reflect the polarity effect of the electric field under a DC electric field.

Therefore, it is also impossible to detect the composition of transformer oil and its polarity effect level

[0004] Insufficiency of current evaluation method for oil breakdown voltage of converter transformer

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