OLTC condition assessment and future trends: An overview

Abstract

The on-load tap changer is a critical device in power transformers for controlling line voltages. Since the OLTC is the only moving part, it is a major source of failure in power transformers. This review presents a comparative study of OLTC technologies-mechanical, hybrid, and electronic—with a particular focus on their condition assessment and fault diagnosis. It outlines both traditional and novel diagnostic approaches and highlights their applicability, limitations, and future development potential. The paper serves as a unified reference for researchers and engineers, combining technological classification, failure mechanisms, and condition monitoring techniques in one comprehensive document.