三相不平衡对配电变压器带负载能力的影响研究

配电网中三相不平衡问题普遍存在,三相不平衡会使配电变压器单相过载导致损耗增加、热点温度升高,进而加快绝缘老化速度、降低变压器带负载能力及运行寿命。文章推导了配电变压器在三相不平衡运行时的绕组热点温度的计算模型,并基于绕组热点温度限制和容许过载倍数限制对三相不平衡时配电变压器的过载能力进行评估,最终给出了各负载类型运行区域的约束条件,为油浸式配电变压器的安全、经济运行提供了参考。

Study on the influence of three-phase unbalance on the load capacity of distribution transformer

In distribution network, three-phase unbalanced operation are widespread. This will cause the problem of single-phase overload about distribution transformer, and then lead to the increase of loss and rise the hot-spot temperature. As a result, the aging rate of insulation is accelerated and has a great influence for the life of the transformer and the load capacity. In this paper, the calculation model of hot-spot temperature under off-center operation of distribution transformer is deduced. Then the overload capacity of the distribution transformer is evaluated based on the limit of hot-spot temperature and the allowable overload factor. Finally, the constraint conditions of each load type are given. This paper provides a reference for the safe and economical operation of oil immersed distribution transformers in power grid.