Condition Based Monitoring - Endwinding Vibration
Generator stator windings outside of the stator core are referred to as the end-winding. The endwinding is at high-voltage and requires support against mechanical vibration driven by magnetic and mechanical forces. Machine endwindings are designed so that under normal circumstances these vibrations are controlled enough to prevent significant movement. However, the endwinding support system can deteriorate due to:
- Looseness of the endwinding support and tie structure due to mechanical aging and thermal expansion.
- Resonance conditions close to the primary mechanical forces of rotational frequency and twice the AC line frequency.
- Relative motion between one component and another which can abrade the high voltage insulation on the coils.
Endwinding vibration can lead to cracking of the coil/bar insulation just outside of the stator slot and, in severe cases, may cause the copper conductors to fatigue crack leading to high arcing currents. Eventually, any of these issues can lead to stator winding ground faults.
Endwinding vibration monitoring using fiber optic accelerometers provides a means to warn operators when dangerous vibration levels begin to occur.
