AQ: Synchronous generators inter-turn faults
For the MW range of Synchronous generators, there is no terminology of “interturn fault” on the stator winding. There could only be coil to coil fault on the stator for such size of machine design.
There are possibilities of having inter-turn faults on the rotor winding: when the insulation positioned between adjacent conductors break (electrically) over time under certain mechanisms. These mechanisms can include; turn to turn movement caused by thermal expansions (during starts/stops cycles), rotor coil shortening, end strap elongation, inadequate end-turn blocking or conductive bridging formed by contamination. The protection of avoiding the interturn insulation is a function of how well the machine is designed, maintained and operated. The OEM of the generator usually provides recommendations to avoid any inter-turn fault during the lifecycle of the machine. Saying this, there are ways to monitor the interturn fault indication; such as data acquisition (air gap flux probe, air gap search coil), as supportive monitoring (RSO, Shaft voltage, shaft vibration levels, excitation current etc.). Ideally, you have to be knowledgeable with the machine design to interpret the acquired data to make valuable predictions.
If you start by contemplating what kind of symptoms inter-turn faults could give rise to, you will be part of the way.
While machine is at standstill, you could do some reflected-wave analysis. All phases should show (near) identical responses.
During operation, you could have non-identical current and voltage waveforms on the three phases (you must compensate for unequal load).
You may experience strange sounds, in the supersonic range. Changing for different locations around the stator. You can continue the list, and settle on systems that may be able to detect any anomalies, so you can react accordingly.
