Measurement and analysis of transient overvoltage distribution in the low-voltage winding of 1000 kK power transformer without oil immersion

• Published in: IEEE transactions on dielectrics and electrical insulation 2014-08, Vol.21 (4), p.1835-1841
• Main Authors: Wang, Zhe, Wang, Tonglei, Zhang, Qiaogen, Yin, Yu, Shi, Weidong, Chen, Weijiang
• Format: Article
• Language: English
• Subjects: Coils; distributed capacitive sensor; measurement method; Oscillators; transformer winding; Transient analysis; Transient voltage distribution; Transmission line measurements; voltage gradient distribution; Voltage measurement; Windings
• ISSN: 1070-9878; 1558-4135
• DOI: 10.1109/TDEI.2014.004135

High frequency voltage oscillations will be generated when transient overvoltages intrude into power transformers. These oscillations may cause damage to the insulation of transformers. In this paper, a capacitive coupling sensor array was presented for measuring voltage distributions and voltage gradient distributions in low-voltage winding of a 1000 kV power transformer. A variable impedance transmission line between impulse generator and winding was also designed to avoid distortion of the applied impulses. The results indicate that under the lightning impulse voltages, voltage distributions have been restrained below applied voltage at sandwich-interleaved section but exceed the applied voltage in continuous coils in the first half of the winding and lead to a very nonuniform voltage distribution. Longer duration time will result in a more nonuniform distribution. The amplitude of the transient voltage under steep front square wave reduces faster downward the winding than that under lightning impulse voltages. A shorter rise time will lead to a much worse distribution. In addition, a dominated oscillation of 63 kHz is found under both impulse voltages and steep front square waves.