Experimental Comparison of UHF Sensor Types for PD Location Applications
2009 IEEE Electrical Insulation Conference, (2009)Abstract
In this work, transient response characteristics obtained from different
types of UHF sensors were investigated by means of laboratory experiments.
Three typical UHF sensors (i.e., disc-, monopole- and spiral-type)
were tested using an artificial PD source freely moved around a tank
that was used to represent a small power transformer. The aim was
to identify the UHF sensor characteristics that are most effective
for locating PD sources. A threshold-crossing method based on the
signal power waveform was chosen to determine the arrival times of
UHF signals because it has proved to be effective in many practical
applications. Locating PD sources in the tank depends on time differences
obtained from the arrival times. Our experiments compared the measured
time differences between UHF signals with those expected based purely
on geometrical calculations. Results suggest that disc-type would
allow high ability for determining arrival times accurately, while
the spiral-type illustrates a potential problem of slower energy
build-up with broadband antennas that have a complex and electrically
long structure. This experimental work highlights an important issue
for UHF PD monitoring installations, especially for sensor design
and selection.