EA Technology UltraTEV Plus
2
Operating Manual 2388L015
Page 5 of 66
4. Non-Intrusive Detection of Partial Discharge
Activity
4.1 What is Partial Discharge?
Partial discharges are electrical discharges that do not completely bridge the insulation
between electrodes. The magnitude of these discharges is usually small, however they
cause progressive deterioration of insulation that may eventually lead to failure.
Non-intrusive partial discharge detection provides a means for identifying these potential
sources of insulation failure. If not detected the discharge may result in failure causing not
only in loss of supply to customers and damage to plant but could also endanger staff.
4.2 How can Partial Discharge be detected?
A partial discharge emits energy in various ways and produces a number of effects which
can be detected:
Electromagnetic:
Radio
Light
Heat
Acoustic:
Audio
Ultrasonic
Gases:
Ozone
Nitrous oxides
The most practical techniques for non-intrusive testing are based on the detection of the
radio frequency part of the electromagnetic spectrum and ultrasonic emissions. The
UltraTEV Plus
2
has specifically been developed to enable electromagnetic and ultrasonic
activity to be detected in a single simple to use instrument.
4.3 Airborne Ultrasonic Discharge Activity
Acoustic emissions from partial discharge activity occur over the whole acoustic spectrum.
Audible detection is possible but depends on the hearing ability of the individual. Using
an instrument to detect the ultrasonic part of the acoustic spectrum has several
advantages; instruments are more sensitive than the human ear, are not operator
dependent and are more directional when operating above the audible frequency.
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