110kV变压器中性点过电压的计算及其保护策略  

Calculation of Overvoltage on Neutral Point of 110 kV Power Transformers and Corresponding Protection Strategy

作　　者：于化鹏[1] 陈水明[1] 余宏桥[1] 杨鹏程[1] 印华 吴高林 

机构地区：[1]电力系统及发电设备控制和仿真国家重点实验室(清华大学电机系),北京市海淀区100084 [2]重庆电力科学试验研究院,重庆市渝北区401123

出　　处：《电网技术》2011年第3期152-158,共7页Power System Technology

摘　　要：为了限制短路电流和满足继电保护整定的需要,110 kV系统采用的是部分变压器中性点接地方式,这种接地方式会使不接地变压器的中性点产生过电压。为此使用PSCAD/EMTDC软件计算了重庆电网一个110 kV系统中不接地主变中性点的过电压。计算结果表明:不接地变压器中性点的工频暂态过电压最高可达到125.8 kV;不接地系统下发生单相接地故障时,变压器中性点电压会上升到相电压;非全相运行时空载变压器中性点可能会产生铁磁谐振过电压,峰值可达到261.2 kV,严重威胁中性点和线端设备的安全;雷电过电压也会损坏中性点的绝缘,也需加以限制。最后给出了适用于110 kV变压器中性点的保护配置方案,并指出当采用间隙和避雷器并联保护时,需考虑避雷器对中性点工频暂态过电压的限制作用。To limit short-circuit current and meet the requirement of setting of relay protection equipments, the partial neutral grounding of power transformers is adopted in 110 kV power systems in China, and this kind of grounding mode will result in overvoltage on the ungrounded neutral of power transformer. The overvoltage on ungronnded neutral of power transformer of an 110kV system in Chongqing power grid is calculated by PSCAD/EMTDC software. Calculation result shows that the maximum power frequency transient overvoltage on the ungrounded neutral of power transformer will be 125.8kV; the voltage on the neutral of power transformer will came up to phase voltage while single-phase earth fault occurs in ungrounded system： under the condition of open-phase operation the ferro-resonance overvoltage with peak value of 261.2kV may result in the neutral of no-load power transformer and such a peak value seriously threatens the security of power equipments and the insulation of transformer neutral; lightning overvoltage can damage the insulation of transformer neutral, so it should be limited as well Finally, a protection configuration scheme that is suitable to the neutral of 110kV power transformer is given, and it is pointed out that when air-gap and arrestor are parallelly adopted, the restriction of arrestor on power frequency transient overvoltage on the neutral of power transformer should be taken into account.

关 键 词：中性点 变压器 避雷器 间隙 工频过电压 雷电过电压 

分 类 号：TM77[电气工程—电力系统及自动化] TM86