Research on Gas Protection Misoperation Mechanism and Strategy in Switching Process of On-Load Tap Changer for Large Capacity Transformer

The arc generated when the on-load tap-changer (OLTC) is switched can cause the insulating oil inside the oil tank to surge. With the increase of transformer capacity, the oil surge is very severe due to the large arc current during the switching process, and the gas protection misoperation accident occurs frequently. This paper first analyzes the characteristics of the oil flow velocity in the connecting pipe of oil conservator when faults of different severity occur, and then compares it with the oil flow velocity characteristics in the case of normal switching of OLTC. Finally, according to the difference of flow characteristics in two cases, two strategies for dealing with gas protection misoperation are proposed. One is to reset the settings of the gas protection, and the other is the delay strategy.