General reports/writings connected with the Insulation Diagnostics project
This is a small subset of the many, often trivial, reports and
summaries that I've often started, and less often finished, sometimes
just for my own thoughts or sometimes to try to get comments from
other people. Several of these are in part literature reviews, but
some contain new data also.
Perhaps there'll be something to interest people from outside the
division.
-
lightning.pdf: a summary of several books that I've read,
on the subject of the nature of lightning, and on means of
protection from it.
-
review_pd_measurement.pdf: a review of a few dozen references
on PD (partial discharge) detection and measurement.
This, like most files linked on this page, was written by me and
mainly for me. The intention was that my thoughts are in brackets
([...]), and the rest reports the claims of the papers. In fact,
there are a few other of my views/comments in the main text.
-
review_dielectric_measurements.pdf: a summary of mainly two
references, about low-level measurements and dielectric measurements;
as usual, this was supposed to go further, but was forced to be
cut short by the end of the holidays...
-
pd_in_stator_insulation.pdf: a literature review on the
characteristics of partial discharges (PD) in the (usually) epoxy-mica
composite insulation of stator windings.
-
sic_endgrading_material_properties.pdf: a literature review and
some own measurements, considering good material descriptions of the
SiC-powder based composite used for grading the electric field around
the stator-slot to end-winding overhang regions of HV stator windings.
-
effect_of_recent_excitation_on_stator_pd.pdf: when making
PD (partial discharge) measurements, one would like the
results to be reproducible (to a modest degree of similarity);
it is well known that some `warming up' time of applied voltage
is useful in order to get the insulation closer to a steady state
of PD. With the variable-frequency PD measurements of interest
in this project, the steady state approached at each amplitude and
frequency of applied voltage is different from that of the
next point, which causes results to depend on the order of
application of these amplitude/frequency points. This report
of some lab work shows the extent of the variation, and suggests
ways of getting a result closer to the equilibrium value,
in reasonable time.
-
pd_signal_transmission_in_stator_windings.pdf: PD measurements
on large, inductive apparatus are known to have the problem of
resonances and postition-dependent attenuation. These effects
are important in the current project, as they affect how
much similarity there can be between the measurements of stator
PD by the DS and PD systems. This report surveys literature,
mainly from the 1990s, about pulse propagation in stator
windings. The consensus is that there is a `good' frequency
range of low values, around 10 -- 100 kHz, where attenuation
is small, and that attempting to measure more of the much wider
potential spectrum will result in much greater measured values of
nearby pulses than of more distant pulses.
-
thoughts_on_experimental_methods_with_pd.pdf: this is
rather messy, and was intended to be much more thorough --
it is the result of reading several books about experimental
design and research methods while on holiday... partial
discharge is so stochastic and so time-consuming in its measurement
(especially at varied low frequency) that it seemed sensible to
give some more serious thought to ways of improving the ratio
of reliable data to time and resources spent.