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This article discusses the breakdown voltage characteristics of gas‐filled transformers and reactors. To determine their insulation characteristics, this study has used models simulating their insulating elements: interturn and section‐to‐section insulation. The study measured 50% breakdown voltages in the section‐to‐section and interturn models under standard lightning impulse voltages that were 1.13 and 1.06 times higher than those under the standard switching impulse voltages, respectively. The mechanism of the above‐mentioned facts is discussed, in terms of the formative time lag of the discharge. © 2020 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

In this paper, the amount of SF6 decomposition gases due to the partial discharge (PD) was studied in the SF6 gas-insulated transformer. The long-term PD degradation experiment was performed while controlling the discharge magnitude using the surface discharge, and the gas generation amount was measured by using gas chromatography for SO2F2, SOF2, SO2, CO, and CF4. In addition, to investigate the relationship between the partial discharge energy and the decomposed gas generation amount, partial discharge energy was calculated by a data processing program and converted to the unit of joule per mole. With the finite element method (FEM), the electric field distribution and SF6 gas decomposition mechanism were explained for the partial discharge energy effect on the gas generation. This study helps understand the relationship between the partial discharge energy and the decomposed gas generation ratio with the experimental results and can be used for the diagnosis of PD and maintenance process for the gas-insulated transformers.

Concentrations of population and business activities result in high energy demand in urban areas. This requires the construction of underground substations. Oil-free, nonflammable, nonexplosive equipment is recommended for underground substations. For this reason, gas-insulated transformers have been developed. A diagnostic method for gas-insulated transformers is thus required. This paper provides an experimental survey of the main components of decomposition gas generated by various faults in gas-insulated transformers carried out through simplified model tests. The phenomena of overheating and partial discharges are modeled, taking the actual materials related to each fault into account. For example, CO, CO2, and aldehydes are produced by overheating of pressboards and PET films. The amount of gas produced increases with rising temperature. While various gases are produced from a partial discharge, the principal components are SO2 and SOF2. These results will be used to develop a diagnostic method for gas-insulated transformers. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 48–58, 2000 [ABSTRACT FROM AUTHOR]

The improvement of the cooling-gas velocity distribution over the coil windings in SF6 gas transformer is very important to achieve high quality for designing. In this paper, the application results of the reflective-type ultrasonic wave method to measure the cooling gas distribution in the SP6 gas transformer are reported. This measurement can be performed without disturbance of the gas flow by the presence of the sensors, and this method is demonstrated to be more effective than the conventional fluid velocity measuring method. In this measurement, the velocity of gas flow at some locations in the transformer was not proportional to the volume of the input gas flow. It can be divided into three patterns corresponding to the location as follows. (a) Gas velocity increases with the increase of the input gas flow amount. (b) Gas velocity is constant regardless of the increase of the input gas flow amount. (c) Gas velocity decreases with the increase of the input flow in the first, and changes to increase with the further increase of the input flow. These characteristics are compared with the computational results of gas flow analysis. © 1998 Scripta Technica. Electr Eng Jpn, 122(3): 1–9, 1998 [ABSTRACT FROM AUTHOR]

This paper deals with the partial discharge inception voltage (PDIV) and breakdown voltage (BDV) characteristics of turn-to-turn insulation models for SF6 gas-insulated transformers in the presence of steep-front short-pulse voltages, whose waveforms are 35/65 ns and 50/370 ns. It was determined that PDIV at nanosecond pulses were 1.05 to 1.15 times higher than those at standard impulse voltages and that the BDV at nanosecond pulses were about 1.4 times higher than those at standard impulse voltages. The ratio of impulse PDIV to ac PDIV is 1.40 to 1.48 for standard impulse voltages and 1.32 to 1.37 for switching impulses. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 36–43, 1997 [ABSTRACT FROM AUTHOR]

In this paper, the amount of SF6 decomposition gases due to the partial discharge (PD) was studied in the SF6 gas-insulated transformer. The long-term PD degradation experiment was performed while controlling the discharge magnitude using the surface discharge, and the gas generation amount was measured by using gas chromatography for SO2F2, SOF2, SO2, CO, and CF4. In addition, to investigate the relationship between the partial discharge energy and the decomposed gas generation amount, partial discharge energy was calculated by a data processing program and converted to the unit of joule per mole. With the finite element method (FEM), the electric field distribution and SF6 gas decomposition mechanism were explained for the partial discharge energy effect on the gas generation. This study helps understand the relationship between the partial discharge energy and the decomposed gas generation ratio with the experimental results and can be used for the diagnosis of PD and maintenance process for the gas-insulated transformers. [ABSTRACT FROM AUTHOR]