Analysis of overheating of Voltage transformers (VTS) in high-voltage substations

Voltage transformers (VTS) are vital components in high-voltage substations, providing precise voltage measurement essential for protection, control, and metering systems. However, overheating of VTs poses a significant threat to substation reliability by accelerating insulation aging and potentially leading to catastrophic failures. This paper presents a comprehensive analysis of the causes behind VT overheating, including electrical overload, harmonic distortion, cooling deficiencies, insulation degradation, and mechanical faults. By reviewing diagnostic techniques such as continuous temperature monitoring, infrared thermography, partial discharge detection, and dissolved gas analysis, this study highlights effective early-warning strategies. Field data from multiple substations in Iran is examined to illustrate real-world failure modes and maintenance challenges. Finally, the paper proposes best practice maintenance strategies and operational recommendations to enhance VT longevity and reliability, supporting stable grid operation.

Keywords:

Voltage transformers , high-voltage substations , overheating