Re: Spark-gap sparks vs. solid-state sparks

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Richie,

Yes - most true Partial Discharge (PD) events typically have risetimes of
several nanoseconds, and durations of tens of nanoseconds. The Corona
flashes or streamer flashes I described in my previous posting are
physically much larger, so their risetimes and durations tend to be longer
(i.e., 10's of nanoseconds risetime and hundreds of nanoseconds in
duration). True PD events are characterized by impulse-like spikes of
current as small increments of charge are suddenly redistributed by a
corona discharge. A PD event is accompanied by a step function change in
voltage, a pulse of RF energy, emissions of sound and light, and may also
be accompanied by emission of gas (breakdown products of a solid or liquid
dielectric). PD testers "listen" for various transient signatures in a
variety of ways, including RF detection, acoustic emission, di/dt or dv/dt
impulse detection, etc. As you suggest, some PD detectors use a narrow band
resonant circuit that is shock-excited by a PD impulse - the height and
area of the resulting "ringing" can then be used to estimate the change of
charge that occurred during the event. PD testing is often used for testing
HV cables, power transformers, HV motors and generators, capacitors, and HV
bushings. 

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "R.E.Burnett by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <R.E.Burnett-at-newcastle.ac.uk>
> 
> Hi Bert,
> 
> You said that these transfers occur over nanosecond time frames.  Is this
> behaviour the source of the RF that partial discharge detectors listen
> for ???
>                                                         -Richie,
> 
> > Original poster: "Bert Hickman by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>
> >
> > There's some evidence (again via Bazelyan) that corona and streamer flashes
> > represent mostly a capacitive load to the HV electrode, and that current
> > may not only be "injected" into the surrounding region when the topload is
> > positive, it may also be "extracted" from the surrounding space charge when
> > the topload polarity reverses, returning some of the surrounding space
> > charge back to the topload. If this is primarily a "reactive" transfer, the
> > impact on Q would be minimal, while still impacting Fo of the secondary...
> >
> > -- Bert --