On-line monitoring of power transformers and components: a review of key parameters

The IEEE Transformer On-Line Monitoring Task Force is developing a guide for the on-line monitoring of power transformers, its components, and accessories. Publication of the guide is expected in mid 2000. This paper gives an overview of the key parameters that can be monitored on-line (dissolved gas-in-oil analysis, moisture-in-oil, partial discharge, oil temperature, winding temperature, load current and voltage, insulation power factor and pump/fan operation). The techniques to monitor instrument transformers are then discussed (tan /spl delta/ and relative capacitance measurements, gas analysis, PD measurement, and pressure measurement). The paper also discusses measurements of bushings and load tap changers.