Views
4 years ago

Stator Winding Partial Discharge Activity for Marine Air-Cooled ...

Stator Winding Partial Discharge Activity for Marine Air-Cooled ...

Stator Winding Partial Discharge Activity for Marine Air-Cooled

Vicki Warren Qualitrol - Iris Power - Toronto, Ontario Canada Stator Winding Partial Discharge Activity for Marine Air-Cooled Generators ABSTRACT Maintenance personnel need as much advanced notice as possible and ease of reliable data collection when problems develop within the stator winding insulation system of air-cooled generators on marine vessels. Unfortunately, traditional off-line testing does not provide this, as tests are not done under normal circumstances due to mechanical, thermal, ambient and electrical stresses. Partial discharges (sometimes also known as corona) are known to occur in deteriorated stator winding insulation systems, as well as new systems with manufacturing or installation flaws or shortcomings. Therefore, Partial Discharge (PD) activity is an indicator of the presence of some deterioration mechanisms at work within, or on, the solid insulation of the stator windings of high voltage rotating machines. Although off-line PD has been used for marine vessels, it fails to detect problems related to mechanical, thermal, ambient and even normal electrical stresses. Advances in on-line detection and measurement of partial discharges has resulted in monitoring equipment that provides a knowledgeable user with reliable and repeatable information regarding the behavior of an insulation system while a machine is in operation. This paper will highlight some of the limitations and benefits of traditional off-line testing and on-line PD testing using case studies and signal analysis from marine vessel applications. INTRODUCTION Generators in marine vessels are often multi-turn coils manufactured using a mica-based system and global vacuum-pressure-impregnation (VPI) process. Due to the complexities present during the impregnation process and inadequate acceptance testing, improper impregnation is more probable in global VPI stators than traditional batch VPI or resin-rich tapes. This can occur as the result of inadequate vacuum or pressure, too high resin viscosity, improper temperatures or foreign objects embedded in the tapes. In the presence of voltage stress, partial discharges will occur across these voids and attack the organic resin. This attack may lead to strand or turn shorts if the voids are near the copper conductors, and eventually multi-turn coil failure will occur. If the voids are in the center of the groundwall insulation thickness, they are more benign and, as any discharges that take place within them are of low magnitude, failure due to the presence of voids can take many years. An additional problem from improper impregnation is that the internal voids create a thermal barrier inhibiting the transfer of heat from the copper to the core [1][2]. A typical design for marine generators includes multiple circuits per phase which results in a high number of high voltage coils and turns per coil. Though the overall current output is relatively low, this design presents some unique susceptibility to premature failure mechanisms. In addition, these machines are frequently load-cycled and operated in unique environments, that include wide swings in ambient conditions, exposure to extensive mechanical vibration, and variability of voltage. Because of this, the most common failure processes of the stator winding insulation system in marine generators are: interturn insulation failure, coil movement, and deterioration of the voltage stress coatings. The latter, the stress coatings, is impacted by the variable ambient conditions, but more significantly, the severe harmonic surroundings. Voltage stress coating deterioration does not usually develop into a failure mechanism; however, it can eventually lead to coil movement which can precipitate a failure. Over 50 years of experience with on-line partial discharge (PD) testing in motors and generators rated 3.3 kV or above has shown that years of warning is often given of possible winding failure [3] [4] [5]. These sparks or discharges occur when voids exist in the insulation, or between the insulation surface and the stator core, or between components of different phases. On-line PD testing at variable operating loads and temperatures and ambient conditions detects most (but not all) of the common manufacturing and deterioration problems, including: To be presented at the FMMS 2013 of ASNE conference in August 2013 1

PARTIAL DISCHARGE COURSE - Iris Power Engineering
investigations into the effect of humidity on stator winding partial ...
continuous on-line partial discharge monitoring of generator stator ...
Partial Discharge Testing of Random Wound Stators ... - IEEE Xplore
Partial Discharge Testing of Random Wound Stators ... - IEEE Xplore
A Perspective on Online Partial Discharge Monitoring for ...
experience with partial discharge testing - Iris Power Engineering
Using Partial Discharge and Flux Density Testing to Postpone Stator ...
practical on-line partial discharge tests for turbine generators and ...
EXAMPLES OF STATOR WINDING PARTIAL - Iris Power Engineering
on-line partial discharge measurements on turbine generators ...
Partial Discharge Diagnostics and Electrical Equipment Insulation ...
Partial discharge test to evaluate windings of low - Motor Diagnostic ...
partial discharge testing: a progress report - Iris Power Engineering
propagation of partial discharge and noise pulses in turbine
a new on-line partial discharge test for turbine generators
pas trans 84 - application of partial discharge to hydrogen mtce.pdf
Partial Discharge - Iris Power Engineering
partial discharge testing: a progress report - Iris Power Engineering
Partial Discharge Flyer 2007.qxd - Iris Power Engineering
cigre 06 - experience with continuous on-line partial discharge ...
experience with in-service partial discharge testing of generator
epri 93 - experience with on-line partial discharge testing of motors ...
Cost/Benefit Analysis For Using Partial Discharge Testing
Objective Methods to Interpret Partial-Discharge Data on Rotating ...
American Falls Partial Discharge Activity Study - IRMC 2013
High Frequency Equivalent Circuit Model of the Stator winding in ...
in-service partial discharge testing of generator insulation.pdf
investigation of the voltage influence on partial discharge ...