Preliminary Discussion on Low-voltage Side Single-phase Earthing Protection of

Medium-voltage Distribution Transformer

 

Yang Xudong（Beijing Branch of China Petroleum Engineering Co.，Ltd.，Beijing 100085，China）

 

Abstract According to the understanding of Design Code for Relaying Protection and Automatic Device of Electric Power Installation and design practice，through calculation and analysis of the low-voltage side single-phase earthing protection of the 6~10 kV distribution transformer，it is suggested that，when D， yn11 transformer utilizes high-voltage side over-current protection concurrently as low-voltage side single-phase earthing protection，the sensitivity coefficient can normally meets the requirement；but when Y， yn 0 transformer utilizes high-voltage side over-current protection concurrently as low-voltage side single-phase earthing protection and the sensitivity coefficient cannot meet the requirement，zero sequence current protection on the neutral line of low-voltage side shall be adopted as the single-phase earthing protection.

Key words Single-phase earthing protection Minimum sensitivity coefficient Over-load coefficient Maximum comprehensive coefficient Circuit breaker for total outgoing line

 

摘 要 根据对《电力装置的继电保护和自动装置设计规范》的理解和设计实践，通过对6 ～ 10kV配电变压器低压侧单相接地保护的计算和分析，提出：D，yn11变压器利用高压侧过电流保护兼作低压侧单相接地保护时，灵敏系数一般均能满足要求；而对于Y，yn 0变压器，当利用高压侧过电流保护兼作低压侧单相接地保护灵敏系数不满足要求时，应采用在低压侧中性线上的零序电流保护作单相接地保护。

关键词 单相接地保护 最小灵敏系数 过负荷系数 最大综合系数 总出线断路器