Page 77 - Basic PD Theory

References

slot portion the portion of the coil/bar located within the stator core section
wideband antenna installed beneath the wedges or between the bars, which is capable of
stator slot couplers (SSC)
distinguishing PD based on pulse characteristics
the very thin layer of insulating material applied to individual copper strands in a winding
strand insulation
- may be glass fiber, Dacron fiber, enamels, film, etc.
stray current losses the losses attributed to undesired circulating currents within a stator winding - these
currents create heating losses and reduce efficiency
machine protection device that is designed to short-circuit high frequency signals from
surge capacitor lightning or system surges
temperature effect when a change in temperature affects the PD levels
Turbine Generator Analyzer - test instrument for monitoring PD activity using a
TGA
directional sensor configuration
Thermal cycling frequent changes in the machine’s load current due to either real or reactive power swings
a coil insulating system whose binding materials become somewhat soft and pliable with
thermoplastic
an increase in temperature – asphaltic-mica is a classic example
thermoset a coil insulating system whose binding materials set up rigidly and are relatively unaffected
by normal operating temperatures – epoxy-mica is an example
a noise separation technique that compares the arrival of pulses at two different couplers
time-of-arrival to determine the direction of the PD source

top bar the bar closest to the arotor
Continuous PD monitoring systems for monitoring PD activity in hydro and turbine
Tracs
generators and motors – HydroTracs, BusTracs and PDTracs
Second generation continuous monitoring systems for monitoring PD activity in
Trac II
generators and motors
transmission travel of an electrical current through a conductor
turn insulation a dedicated layer of insulation surrounding each turn in a multi-turn coil
vacuum pressure impregnation an impregnation process that involves creating a vacuum, injecting resin, and applying
(VPI) pressure - can be done on a batch of coils or the entire stator
the application of semi-conductive and grading materials to control coil insulation surface
voltage stress control electrical stresses
wedge tap tests an off-line test that involves tapping each wedge to feel, look, and listen for looseness

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