This article focuses on evaluation of in-service power transformerphysical health condition using Health Index (HI) approach. The Health Index (HI) approach is applied by incorporating three key stages such as input for health index assessment, health index estimation and output health index for maintenance decision process of each transformer unit. The first stage is based on condition index, and importance index assessment and also through applying scoring and weight scheme for each test parameter. The condition index of a specific power transformer is evaluated by twelve different diagnostic tests and importance index is assessed from five different factors such as age, loading history, maintenance records, failure/faults, and its location, etc. Numerical weighting and scoring factors were assigned for every test/factor to determine the actual condition of the power transformers with regard to condition and importance aspects. In second stage, By combining the condition and importance index assessment evaluation, the numerical value called Health Index (HI) was estimated, which represent the overall health of a power transformer asset. In third stage, health index estimation results were used to plan for effective maintenance tasks. Through this approach, a case study was performed for 21 in-service power transformers belonging to Tamil Nadu electric utility. The HI results of 21 transformer units were ranked and classified into poor/failed, fair and good, which were further facilitated for Inspection, Repair, and Replacement (IRR) maintenance decisions. Thus, the study is very useful to utility maintenance engineers for better understanding the transformer physical health condition and required maintenance actions timely, which prevents unexpected failure and also reduce cost of maintenance in electric utilities.

本文重点介绍使用健康指数（HI）方法评估在役电力变压器的物理健康状况。通过结合三个关键阶段来应用健康指数（HI）方法，例如，用于健康指数评估的输入，健康指数估计和用于每个变压器单元的维护决策过程的输出健康指数。第一阶段基于条件指标和重要性指标评估，还通过对每个测试参数应用评分和权重方案。通过十二种不同的诊断测试来评估特定电力变压器的状态指数，并根据年龄，负载历史，维护记录，故障/故障及其位置等五种不同因素来评估重要性指数。为每个测试/因子分配了数字加权和评分因子，以确定有关条件和重要性方面的电力变压器的实际条件。在第二阶段，通过将条件和重要性指数评估评估相结合，估算出称为健康指数（HI）的数值，该数值代表了电力变压器资产的总体健康状况。在第三阶段，使用健康指数估算结果来计划有效的维护任务。通过这种方法，对属于泰米尔纳德邦电力公司的21台使用中的电力变压器进行了案例研究。对21个变压器单元的HI结果进行了分类，分为不良/不合格，一般和良好，这进一步有助于检查，维修和更换（IRR）维护决策。因此，