Phase imbalance (i.e., load imbalance among the three phases) causes inefficient use of three-phase distribution assets, resulting in additional reinforcement costs (ARCs) compared to if the three phases were balanced. However, two problems remain unresolved when calculating the ARC: 1) previous ARC formulas assume that the three-phase total peak and the single-phase peak current occur simultaneously, thus causing an underestimation of the ARC; and 2) previous formulas calculate ARC as a point value, using one year's peak load. However, the point value is not credible in supporting making investment decisions on phase balancing. This is because the growth of the yearly peak load is inconsistent over the years – the growth could be positive or negative over the years for low voltage (415 V, LV) networks. To address the above problems, this paper originally develops 1) an updated ARC formula; and 2) a customised approach, named as the cluster-wise probability assessment, to deliver a distribution and confidence range of ARCs for any given LV network. This approach only requires the yearly average current and single-phase peak current, making it applicable to the majority of the LV networks that have a minimal amount of data. Case studies also identify a counterintuitive finding of how the yearly single-phase peak current and the yearly average phase current impact the ARCs.

相不平衡（即三相之间的负载不平衡）会导致三相配电资产的低效使用，与三相平衡时相比，会导致额外的加固成本 (ARC)。然而，计算ARC时有两个问题没有解决：1）以前的ARC公式假设三相总峰值和单相峰值电流同时出现，从而导致对ARC的低估；和 2) 以前的公式使用一年的峰值负荷将 ARC 计算为一个点值。但是，该点值在支持关于相位平衡的投资决策方面并不可信。这是因为年度峰值负载的增长多年来并不一致——低压（415 V，LV）网络多年来的增长可能是正的或负的。针对以上问题，本文最初开发了 1) 更新的 ARC 公式；2) 一种定制的方法，称为集群概率评估，为任何给定的 LV 网络提供 ARC 的分布和置信范围。这种方法只需要年平均电流和单相峰值电流，使其适用于大多数数据量最少的低压网络。案例研究还确定了年度单相峰值电流和年度平均相电流如何影响 ARC 的违反直觉的发现。使其适用于具有最少数据量的大多数低压网络。案例研究还确定了年度单相峰值电流和年度平均相电流如何影响 ARC 的违反直觉的发现。使其适用于具有最少数据量的大多数低压网络。案例研究还确定了年度单相峰值电流和年度平均相电流如何影响 ARC 的违反直觉的发现。