Acoustic Emission (Ae); Surface Tracking; Acoustic Sensor; Specification - Baur PD-SGS User Manual

P D-S G S
6 A
COUSTIC
Acoustic emission is ultrasonic energy that is emitted by discharges on electrical insulating
surfaces or sometimes called Surface Tracking.
6.1

Surface Tracking

Surface Tracking is the formation of a permanent conducting path across an insulator
surface. Usually the conducting path results from degradation of the insulation. Tracking
most readily occurs when the insulation is a carbon based compound.
A high-voltage plant is often very difficult to clean, so dirt and contaminants can build up over
time. In the presence of moisture, these contaminating layers give rise to leakage current
over the insulator surface. This heats the surface and through evaporation causes
interruption in the moisture film. Large potential differences are generated over the gaps in
the moisture film and small sparks can bridge the gaps. Heat from the sparks causes
carbonisation of the insulation and leads to the formation of permanent carbon tracks on the
surface. Under such conditions this process will develop over time and eventually lead to
flashover and full breakdown of the insulation.
6.2

Acoustic sensor

The ultrasonic acoustic sensor is designed for use on air-insulated terminations where there
is a clear sound path between the electrically stressed insulation and the probe. The sensor
is extremely sensitive when pointed directly at the discharge source.
The transducer is embedded into the rubber moulded cover at the front of the device so it
can be easily directed towards the parts of electrical plant where tracking may occur.
6.3

Specification

Specification
Measurement range
Resolution
Accuracy
Convertor sensitivity
Convertor average frequency
822-162-1
E (AE)
MISSION
-6 to +70 dBµV
1 dB
±1 dB
-65 dB (0 dB = 1 V/µbar
level)
40 kHz ± 1 kHz
Ac ous tic E mis s ion (AE )
sound pressure
rms
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