电流互感器短时热电流试验二次绕组烧毁原因及解决方案

Cause and Solution of Secondary Winding Burnout in Short-time Thermal Current Test of Current Transformer

结合国家标准和电力行业标准说明了对二次热稳定性能进行计算的必要性,推导出保护级电流互感器在二次绕组短接情况下二次极限电势值对应的二次电流I_(sALF)的计算公式。比较I_(sALF)与折算到二次侧的额定短时热电流I_(th)’的大小,可以判断出产品设计方案对应的额定短时热电流下铁心磁通密度的状态,给出了不饱和、轻度饱和及完全饱和三种状态下二次电流的计算方法。介绍了容易出现二次绕组烧毁电流互感器的情况,举实例计算并比较I_(sALF)与I_(th)’的大小,结合铁心磁密计算及一、二次电流波形图详细说明了二次热稳定性能的解决方案,在结束语中给出了应该注意的几个常见问题。

The necessity of calculating the secondary thermal stability is illustrated by the national standard and the power industry standard.The formula for calculating the secondary current I_(sALF)corresponding to the secondary limit potential value of the protection level current transformer in the case of the secondary winding short-connection is derived.By comparing the size of I_(sALF)and the rated short-term thermal current I_(th)'converted to the secondary side,the state of the core magnetic flux density corresponding to the rated short-term thermal current of the product design scheme can be judged,and the calculation method of the secondary current under the three states of unsaturated,mildly saturated and completely saturated is given.The situation of secondary winding burning current transformer is introduced.The size of I_(sALF)and I_(th)'is calculated and compared with an example.The solution of secondary thermal stability is explained in detail by combining the calculation of core magnetic density and the primary and secondary current waveforms.