Moisture assessment by FDS & PDC
A large population of aged equipment is apparently contaminated with moisture. Effects on life of Power transformer due to moisture in the solid insulation are:
- Accelerated rate of aging for cellulosic materials such as paper and press board
- Reduction of the dielectric strength of paper and press board materials
- Risk of bubble evolution at high temperatures and limited Overloading capacity
Now a days two approaches are applied; the measurement of charging and discharging currents in time domain (Polarization and Depolarization Currents PDC) and the dielectric spectroscopy in frequency domain (Frequency Domain Spectroscopy FDS) known as DIRANA & provides an indication of the insulation condition such as:
- Moisture content in the oil/paper insulation
- Faults in OIP, RBP and RIP high voltage bushings & CT.
- Faults in the generator, motor and cable insulation
Monitoring of moisture content in solid insulation during maintenance actions such as On- site drying will be very effective and should be considered as an important application.