Page 76 - Basic PD Theory

References

an incomplete, or partial, electrical discharge that occurs between insulation and either
partial discharge
insulation or a metallic electrode
Partial Discharge Analyzer - test instrument for monitoring PD activity using a
PDA-IV differential configuration
PD that is phase-to-phase dependent and originates outside of the slot from
phase-to-phase PD Activity Contamination, electrical tracking, or Phase to phase discharges - clumps 30° phase-
shifted from the classic positions or 15°, 75°, 195°, and 255°
polar 2-D plot that displays the pulse magnitude versus the reference phase-to-ground ac
polar pulse density plot (PPD) sine wave. Color is used to identify pulse repetition rate.
when the Qm of one polarity is greater than that of the other polarity, or there is a
polarity predominance
separation of the two lines on the 2-D plot
polyamide, polimide films an organic resin applied to magnet wire as insulation similar to enamels in appearance
polyester organic resin used to bond tape layers - usually thermoset
when the amount of positive classic PD, near 225°, is higher than the amount of negative
positive predominance
classic PD, near 45° -- indicative of surface activity
positive effect When an increase in the operating or ambient condition causes a increase in PD – can be
attributed to load, temperature, hydrogen pressure or ambient humidity
a type of partial discharge characterized by current pulses of relatively small amplitude,
pseudo-glow discharge and, generally, a long rise time
pulse distribution the pulse distribution pattern can reveal the geometry of the PD sources
2-D plot that displays the pulse magnitude versus the pulse repetition rate in pulses per
pulse height analysis plot (PHA)
second
3-D plot that displays the pulse magnitude and pulse repetition rate with respect to one
pulse phase analysis plot (PPA)
phase-to-ground AC cycle
Qm peak PD magnitude in mV at 10 pps
radiation energy emitted from a central point in the form of waves or particles
radio-frequency any of a range of electromagnetic wave frequencies used for carrier-wave radios and
television transmissions
property of a material that describes its ability to reduce the electric field intensity
relative dielectric constant ε r between charged parallel conducting surfaces
tapes that are epoxy-loaded and are directly applied to the bars - they are cured with heat
resin-loaded tapes (B-stage)
and pressure
rise-time the time required for a pulse to increase from 10% - 90% of its pulse magnitude
RTD resistive temperature detector - used for monitoring stator winding temperatures
either a carbon-loaded tape or paint that is applied to the outside of the portion of the
semi-conducting slot coating
coil/bar that will be in contact with the core - used for voltage stress control
side packing the material used to fill up the space between a coil (bar) side and the stator iron - can be
rigid or conformable and is usually semi conducting
the ratio of the PD signal to the PD-like noise. A high SNR is necessary for noise
signal-to-noise ratio (SNR) separation.
skin effect the phenomenon that current flows on the outside surface of a conductor
discharges that occur on a random basis involving a large surface of coil or bar, separated
slot discharges
from the grounded core by an air gap – positive predominance

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