Experiences acquired during fault diagnosis of generators of Iran’s hydro power plants by measuring partial discharges

In this paper, the results of partial discharge measurements on more than 25 hydroelectric power plant generators have been investigated. All generators’ insulation defects have been considered and a statistical report is made of types of defects and the share of each defect. statistical parameters for different insulation defects are calculated. Using 3-phase partial discharge measurements that performed simultaneously on each machine, enabled us to apply 3PARD (3-Phase Amplitude Relation Diagram) method for differentiating multiple defects and reducing noises. Effect of PD measurement in High and low frequency ranges for different PD types has been investigated and a correction factor for correlating High frequency measurement data with corresponding value in low frequencies has been proposed. Different Types of PRPD (Phase Resolved Partial Discharge) patterns of insulation defects investigated. Considering the effect of load and temperature conditions on these patterns, with several insulating defects noted, the effect of load and temperature changes on these patterns has been analyzed. Considering the effects of load and temperature changes on partial discharge patterns and using amplitude correction factor in high frequency measurements, it is possible to diagnose machines more accurately and have a better estimation of stator’s insulation status.