January 11, 2022

Simple ageless methods for field testing power transformers of no-load condition at the low induced voltage (Analytical review with the aid of transformer field service technicians) – Part I

Introduction Power transformers are key components of the electrical network and require special attention during commissioning and in operation. The importance of correctly assessing the...

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1. Introduction

Power transformers are key components of the electrical network and require special attention during commissioning and in operation. The importance of correctly assessing the condition of a transformer is becoming increasingly important. Already during transport of the transformer from the factory to the place of installation, the transformer may be subjected to mechanical shock exceeding the recommended “g” level. Increasing network complexity, increasing generating capacity, aging transformers reduce their ability to withstand external influences and increase costs in the event of transformer failure due to subsequent extensive outages. Insufficient attention to transformers maintenance can exacerbate the problem. Optimal maintenance means minimizing the cost and time of field tests while obtaining reliable information on the condition of the transformer.

Under external influences on the transformer, failure in the electromagnetic circuit or / and may occur in the insulation: displacement and / or deformation of the windings, damage to the insulation turn-to-turn, layer-to-layer, disk-to-disk, loosening of the compaction of the windings and / or core, displacement and / or deformation of the core, the occurrence of closed loops in the core (core lamination shorts, insulated bolts, pressing bolts, pressing metal rings), loosening of electri cal connections, reduction in dimensions between the active part and the tank, problems with the tap-changer device (LTC or DETC).

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