Video: Generation assets: what six technical webinars teach

Video transcript

Six technical webinars on generation assets, summarised. Partial discharge in motors and generators, the bus that connects them, and what renewable duty cycles are doing to the transformers at the other end. Most of this material is about partial discharge, because in a rotating machine the insulation is what fails. The measurement itself is a tiny high frequency current, and where you listen for it decides whether you find anything. And here is the idea that runs through 3 of these sessions.

The machine already has sensors buried in the stator winding: the temperature RT Ds. They can be used to detect partial discharge as well. Which gives something conventional testing struggles with: location. Compare the magnitude seen at each RTD around the stator, and the defect is near the one reading highest. The bus duct between machine and transformer gets a session of its own, and it opens with the objection. It is an inert system with no moving parts, so why spend anything on it?

And the sensor used there is elegant. A ground path current sensor sits at earth potential on the outside of the enclosure, so there is no high voltage risk, and the polarity of the pulse tells you which side of the joint the discharge came from. One case from these sessions is worth repeating on its own. A disconnect switch was being watched by both partial discharge and temperature. The temperature tripped twice. The discharge had been climbing steeply for at

least two months before the first of those trips. The generator step-up transformer is treated differently from a network transformer, because it is not replaceable in a hurry and it never rests. The most recent sessions are about what renewables have changed. A transformer in a battery storage or wind installation no longer has a steady load profile: it has a duty cycle, and each part of that cycle attacks something different. One consequence of that cycling deserves its own scene,

because it catches people out. Moisture moves between paper and oil with temperature, so the same transformer reads 10 parts per 1000000 cold and over a 100 hot. And the sessions finish with a list of mistakes, which is the most useful slide in the set. Five things these 6 sessions agree on. Generation asset monitoring, from Amperis.