1.impurities, gas and water if dissolved in transformer oil, the impact on the withstand voltage is not great, if the floating state, the breakdown voltage is significantly reduced, the more uniform the electric field, the greater the impact of impurities on the breakdown voltage, the greater the dispersion of breakdown voltage. In the inhomogeneous electric field, impurities on the breakdown voltage effect is smaller, because the local discharge occurs first in the high field strength, so that the oil perturbation, impurities are not easy to form a "small bridge".
2.reduce the impact of impurities measures, transformer and oil contact parts do a good job "dust", "moisture" measures application of vacuum oil filtering equipment for dehydration, degassing, trying to reduce the impact of impurities, such as the use of "oil a barrier "insulation.
Breakdown voltage
Temperature changes in the 0 ℃ -60 ℃ range, damp transformer oil breakdown voltage, often with the temperature increases and significantly increased, the reason is due to the suspended state of water in the oil with the temperature increases into a dissolved state. So that the damp transformer oil in the higher temperature, breakdown voltage may appear maximum, in 60 ℃ - 80 ℃ breakdown voltage is the highest, the temperature is higher, the water contained in the oil vaporization increased, and make the breakdown voltage drop, for the transformer operating fault, more than in the transformer just started a few hours, or load changes in the time period such as the middle of the night and early morning.
Voltage action time
Voltage action time, because after adding voltage, oil impurities gathered to the electrode or medium heating, etc. need a certain amount of time, so the oil gap breakdown voltage with the increase in pressurization time and decline.
Voltage uniformity
Voltage uniformity, oil purity is higher, improve the uniformity of the electric field, can make the breakdown voltage under the frequency or DC voltage increased significantly.
Pressure
Pressure, when the oil contains gas, its frequency breakdown voltage increases with the pressure of the oil, because when the pressure increases, the dissolved amount of gas in the oil increases, and the partial discharge starting voltage of bubbles also increases. However, after the oil is degassed, the pressure has less influence on the breakdown voltage.
Fault gas analysis
When the fault occurs in the inner mass of the transformer, the gas production of these gases will increase rapidly. When the temperature of the fault point is low, the proportion of methane is larger; when the temperature rises, ethylene and hydrogen components increase sharply and the proportion increases. When the serious overheating, acetylene gas will be produced. When the occurrence of solid insulation overheating so on the fault, in addition to producing the above low-molecular hydrocarbon gas, will also produce points more C0 and CO2, and with the rise in temperature, the ratio of CO/CO2 gradually increased. Therefore, during transformer operation, the nature and extent of transformer failure can be determined by regularly measuring the content of various gases in transformer oil.
