Measurement of partial discharges and dielectric losses on rotating machines using damped AC voltages

Measurement of partial discharges and dielectric losses on rotating machines using damped AC voltages

Van Eeden, C.J.

Gulski, E. (mentor)
Quak, B. (mentor)

Electrical Engineering, Mathematics and Computer Science

Electrical Sustainable Energy

High Voltage Technology and Management group

2010-06-01

Large rotating machines in all kinds of applications ages due to operating stresses. Since many years the condition of stator insulation in these motors and generators is investigated using measurement of partial discharge (PD) and dielectric loss factor (tan delta). In particular, off-line and on-line methods of applying PD detection have become common practice. The off-line PD detection technique is based on applying to single phases of the stator insulation an external 50(60) Hz power supply and detecting the partial discharges which inevitably occur in stator insulation. Based on the PD behaviour, the presence and type of discharging defects in the insulation, like slot discharges and end-winding discharges can be identified and evaluated for insulation condition assessment purposes. In contrast to on-line detection, with regard to interpretation rules for off-line PD detection there exist a large amount of experience. Off-line energiz-ing of the stator insulation can also be performed using Damped AC voltages 50-500 Hz (DAC), which has the advantage the test equipment is more mobile than AC test sets. This study describes the measurement technique of off-line PD and dielectric loss detection on stator insulation using damped AC. A test procedure for DAC is proposed based on the applicable AC standards, and results of DAC PD and dielectric loss measurement are presented. Based on laboratory investigation on a full scale stator insulation system as well as during field inspections on large motors, a comparison has been made of dielectric loss behaviour and PD behaviour – like tan delta levels, PD levels and phase resolved PD patterns – at 50 Hz AC stresses and at oscillating voltages. The usefulness of PD detection at oscillating voltage waves, and the usage of AC interpretation rules, has been discussed.

damped AC
DAC
test procedure
data processing
partial discharges
dielectric losses
rotating machines
stator insulation
condition monitoring
tan delta

http://resolver.tudelft.nl/uuid:42788ce0-06a6-463b-a667-0db979694586

2011-06-01

Student theses

master thesis

(c) 2010 Van Eeden, C.J.