The test enables predictive maintenance on hydro generator stator windings, resulting in the increased availability and extension of operating life. The technique was introduced more than three decades ago and has since been used on over 5000 hydro generators to identify deteriorated stator windings.

The method is non-destructive and based on proven scientific and empirical principles and is recommended by manufacturers and industry standards such as the IEEE Std. 1434-2000.

The monitoring technique is based on the application of 80pF capacitive couplers, resulting in a high frequency measurement range and a favorable signal-to-noise ratio. This enables the automatic separation and recording of both partial discharges and noise, so that test results can be easily interpreted by users. The most common method of monitoring hydro generators involves using an Iris Power PDA-IV portable instrument with multiple sets of permanently installed capacitive couplers. The instrument is controlled by means of a computer and includes WindowsTM–based control and data display software.​

• the root causes of stator problems can be identified and often repaired at an earlier stage.
• the monitoring can increase the availability of generators, and can contribute to the extension of the useful life of the unit stator winding

• intervals between generator inspection outages can be increased, if the PDA results are good
• most stator winding in-service failures can be avoided
• there is an exceptionally low rate of false indications
• clear levels at which machines need maintenance have been established
• can be applied to existing and new hydro generators.