110和220kV不接地运行变压器中性点保护方式

为保护110、220 kV不接地运行变压器中性点绝缘,并克服间隙、避雷器等现有保护方式存在的缺陷,推荐一种新型可控间隙与金属氧化物避雷器并联保护方式,可控间隙与避雷器共同配合以实现对变压器中性点的有效保护。当系统发生单相接地且失地或非全相运行故障时,可控间隙动作以保护变压器中性点绝缘,同时,避雷器被短接,以免避雷器在工频过电压下运行发生危险。雷电过电压下,可控间隙不动作,由避雷器动作限制变压器中性点过电压。其他过电压下,可控间隙和避雷器均不动作,变压器中性点绝缘能够耐受。可控间隙与避雷器并联保护方式可有效保护变压器中性点绝缘,并解决了现有保护方式存在的问题,具有一定的工程应用价值。

A Protection Mode for Ungrounded Neutral Points of 110 kV and 220 kV Power Transformers

To protect the insulation of ungrounded neutral points of 110kV and 220kV power transformers and remedy the defects of existing protective measures such as gap and arresters,a novel protective mode in which the controllable gap is in parallel with metal oxide arrester(MOA) is recommended.In this protective mode the controllable gap is coordinated with MOA to effectively protect the insulation of ungrounded neutral points of power transformers.When single-phase grounding fault occurs while the grounding of neutral point is damaged or open-phase operation occurs,the controllable gap operates to protect the neutral point insulation,meanwhile the MOA is short-circuited to avoid the damage of MOA due to its operation under power frequency overvoltage;the controllable gap does not act while lightning surge occurs;under other kinds of overvoltages both controllable gap and MOA do not act and neutral point insulation of power transformer can withstand these kinds of overvoltages.The parallel protection mode of controllable gap with MOA can effectively protect the insulation of power transformer neutral points,and this protection mode can remedy defects of existing protective modes,so it is available for engineering application.