Synthesis of a Decade of Experience in Proactive Maintenance of Generation Assets in a Hydro-Electric Power Plant

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Dr Raja Kuppuswamy
Dynamic Ratings


Paper Authored by

Dr. Raja Kuppuswamy
Dynamic Ratings

Sandy Rainey
NCPA Hydroelectric Operations

Availability of a power plant depends crucially on the reliability of major high voltage components such as the generator, isolated phase bus (IPB) and the generator step-up transformer (GSU). The condition of these assets is determined most often through periodic manual inspections during an outage.  These inspections look for obvious problems such as physical damage, frayed connectors, degraded insulation, and evidence of overheated components. 

The disadvantage of periodic inspections is that the time interval between two consecutive maintenance activities is not always sufficient to identify developing issues prior to failure. Periodic maintenance is often performed when the asset is not in service or the plant is in outage and the actual state of the asset with respect to time and plant operation condition is often not available for diagnosis. Periodic maintenance frequently results in the maintenance of healthy assets, increasing maintenance costs, and the possibility of human error. We decided to employ continuous condition-based monitoring to collect data generated during the asset’s normal operating conditions to get awareness to problems in real time.

High voltage assets in a power plants are interconnected and when they are monitored in isolation, it could result in false conclusions of the origin of the fault sources and false alarms.  This is often an overlooked issue and we addressed this using a choice and combination of conventional and unconventional sensors.  To evaluate each individual asset, we selected a group of key monitoring parameters, primarily based on general industry experience and their proven diagnostic value.  In this paper, we have focused on presenting and discussing only partial discharge and power-factor test results along with the synthesis of more than a decade of experience using these methods.


Raja Kuppuswamy is senior principal engineer at Dynamic Ratings (DR) Inc., based in Sussex, United States.  In 1996, he earned his PhD degree in high voltage engineering for his doctoral thesis on the study of the aging life-cycle of power transformer insulation using partial discharge pattern recognition techniques.

Over the next 22 years, he pioneered the development of eight partial discharge measurement and analysis tools based on ultra-high frequency, ultrasonic and traditional PD sensing technologies.

Prior to joining DR, he held product management, sales and technical services positions at ABB, Alstom, Crompton Greaves, Haefely in France, India, Sweden and Switzerland. He served in CIGRE, France and IEC, Switzerland technical committees on partial discharges. He is senior member IEEE, holds 4 patents and 120 scientific publications.

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