Transformer Tapchanger Condition Assessment

This chapter provides an overview of the design, construction, reliability, and failure modes of tap-changers, both on-load (OLTC) and de-energised (DETC), which are essential components in electrical power systems for voltage regulation and stabilization. The failure modes are categorised into thermal, dielectric, mechanical, and chemical, offering insights into the various issues that can affect tap-changers function and reliability. The range of condition assessment techniques essential for early detection and mitigation of potential failures is presented. These techniques include internal inspection, oil tests, dissolved gas analysis, dynamic resistance measurement (DRM), vibro-acoustic measurement (VAM), temperature monitoring, and motor torque analysis. Each method is discussed in detail, providing information on their application, benefits, and limitations in assessing OLTC condition and predicting potential failures. This chapter is meant to serve as a basic resource for professionals in the electrical power industry, offering practical guidance on ensuring OLTC reliability and performance through effective design, construction, maintenance, and condition assessment techniques.