Page 73 - Basic PD Theory

References

I. Glossary

Term Definition

absolute dielectric constant ε 0 8.85418781762 E-12
aging the development of failure mechanisms
amplification An increase in magnitude
asphalt Thermoplastic binder to consolidate insulating tape layers
attenuation a reduction in magnitude
coils made in half-sections for easier installation in long core or small diameter bore
bar (half coil)
machines - one turn per coil
bottom bar the bar furthest from the rotor
breakdown voltage the voltage at which a pulse spark will occur across a void
capacitance is the electrical property that stores an electrical charge by impeding a change in voltage
PD sensors that block the 50/60Hz signal and pass the high-frequency PD signals (80pF
capacitive couplers
capacitors)
capacitive coupling travel of a high-frequency signal due to the capacitance property of materials

pulses that occur within the slot portion of the coil and are phase-to-ground voltage
classic PD pulses
dependent - negative clumps near 45° and positive near 225° on the 3-D plot
cold tests tests at lower than normal operating temperatures - compared to hot tests to find
temperature effects
low magnitude sparks that occur as an energized coil intermittently vibrates against the
contact sparking
grounded core
Contamination the presence of any conductive material in the endwinding area
corona visible arcing that occur when the gas adjacent to an exposed conductor ionizes
PD that is dependent on the phase-to-ground voltage of another phase - clumps +/-
cross-coupled PD activity
120° from the classic positions
Dacron a synthetic organic material that is usually woven
often called da-glass - refers to a mixture of glass and dacron fibers formed as a thin
Dacron/glass
insulating layer on magnetic wire
the loss of mechanical strength of a resin which bonds layers of insulting tape together;
debond
also called delamination
delay time In a directional (BUS) install, the time in nanoseconds it takes for a high frequency pulse
to travel from one coupler to the other
a style of sensor installation that uses simultaneously pulse arrival for disturbance
differential (PDA) separation – primarily used in hydrogenerators
a style of sensor installation that uses arrival time for disturbance separation – primarily
directional (BUS)
used in turbine generators, motors and small hydrogenerators
dispersion An increase in rise-time - lower frequency characteristic
the theoretical V/mm stress of a gas medium that if exceeded will result in an arc - for air
electrical breakdown
it is E BD = 3kV/mm at STP

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