This paper introduces the three situations where the asymmetry of three - phase current takes place and proposes the calculation methods of the annexed line losses and of loss reduction when the addition of the three - phase current load is not equal to zero because of the asymmetry of the three phase load 摘要阐述了三相不对称电流的三种情况，并提出了因三相负载不对称而引起的三相电流相量之和不为零时的附加线损的计算方法及降损措施。
