Sterilization of Dry-Type Transformer Winding by Conducting Short-Circuit Test in Nuclear Power Plant: A Case Study

Dry-type transformers play a vital role in power distribution to many loads at different voltage levels in a nuclear power station. Usually, dry-type transformers are located indoor with appropriate heating, ventilation and fire protection. The dry-type transformers in NPPs are less loaded due to redundancy in design. The maintenance program for transformers in NPPs calls for stringent requirements and overseen by multiple regulating authorities. Even though an effective maintenance program is in effect, there were few occasions where a dry-type transformer has failed and could not be foreseen during regular maintenance. Also with growing nature of deregulation in electrical markets, the failure probability of transformer increases simultaneously. A transformer failure in a nuclear power plant (NPP) can result in significant damage to critical loads, serious safety implications and revenue loss as well. Hence, a distinctive maintenance program should be adopted in order to ensure the healthiness of dry-type transformer. This paper describes a case study made to analyze the procedures for maintenance of dry-type transformers by conducting sterilization techniques at a specified interval in order to improve reliability. The results of this case study were extraordinary and successfully improved transformer life. Owing to the results, the revision of existing procedures followed in other NPPs is recommended.