Mathematical analysis on power frequency discharge characteristic of air-water two-phase flow combined protection gap for transformer neutral points

作者：Li Bojiang; Wen Xishan; Yan Yuting; Li Boyang

来源：Power System Technology, 2014, 38(7): 1786-1791.

DOI：10.13335/j.1000-3673.pst.2014.07.011

• Mathematical analysis
• Neutral points
• Power frequency
• Protection gap
• Water flows

The research on discharge characteristics of air-water two-phase combined fluid is of significance in the fields such as wastewater treatment, high-voltage insulation, underwater sound source and the protective gap for power transformer neutral points. A power frequency discharge test of combined air-water gap composed of different total length of air-water gap and different length of spray water is made under laboratory condition to analyze the variation law of the discharge characteristic. Research results show that the combined air-water gap is more easy to be broken down than the air gap with the same length; under constant total length of combined air-water gap the form of the discharge characteristic curve is similar to V-shape; under different total lengths of combined air-water gap the positions of the lowest points of the discharge curves are different and with the increase of the total length of combined air-water gap the positions of the lowest points shift to upper right; under different total length of combined air-water gap the parts of the three discharge characteristic curves located at the right side of the lowest points are similar to straight lines and are almost coincided; under different total length of combined air-water gap the forms of parts of discharge characteristic curves located at the left side of the curves' lowest points are linear and shift to upper right along with the increase of the total length of air-water gap; as for a protection measure for power transformer neutral points the combined air-water gap is more superior than traditional protective air gap. Based on the analysis on test results, through numerical fitting of test data a mathematical analytical formula for combined air-water gap is established. According to the established mathematical analytical formula the breakdown voltages of the combined air-water gap under different total length of combined air-water gap and different length of spray water as well as the position where the lowest breakdown voltage can be calculated and the calculation results are available for reference to the application of protective gap for power transformer neutral points.

• 出版日期2014