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Acoustic testing of busducts

Acoustic testing of instrument transformers

Acoustic testing of cable joints and bushings in the switchgears

Acoustic testing of the switchgears

Acoustic testing of power transformers

Implementation of the system of control of electrical insulation characteristics

New approaches to monitoring of the technical condition of the switchgear equipment



To detect insulation defects accompanied by partial discharges inside busducts of 6-10 kV, the acoustic method is the most effective non-invasive diagnostic method which is performed under operating voltage. Detection of defects in busducts and timely repairs allow avoiding unplanned outages.

The survey is conducted under operating voltage without disconnecting and removing the load, usually before the scheduled maintenance. The survey is conducted in accordance with the approved methodology. Recommendations about hazard criteria of partial discharges and making decisions on the need for repairs are based on the amount of acoustic signal. Usually discharges in busducts are related to relaxing of the joints of the support insulator to the bus. At this point there may be spark discharges on a "floating potential." In addition, there may be partial discharges in the cracks of insulators.

Equipment used for surveys: acoustic partial discharge sensors like РЧР, digital oscilloscope АСК-3107, computer, ultrasonic moderator "Dolphin".

Acoustic sensors are installed manually or with a rubber mount in the control point on the insulator ring with lubricant ЦИАТИМ. Ultrasonic moderator "Dolphin" converts the signals from sensors into digital form, stores the data, stretches the signal in 100 times, and is able to reproduce it. With the use of a computer, the analysis of the spectrum of the ultrasonic signals can allow to determine the type of defect. The fact that the observed signals are sparks is also confirmed by TrEasyAnalyzer discharge sounds recognition program, developed at the Physics Department of Moscow State University. Test points are selected in the neighborhood of the insulators on the insulator ring. Defective insulators are marked with a cross.

For example, during the survey of 10 kV bus systems the signals were detected from the discharges in the insulator rings of all phases of vertical sections of bus systems ШТ-Г-2 in the engine room under the generator. The signals are of high frequency spectrum and repeat the frequency response of the sensor. Therefore we can conclude that the source of the signal is an electrical discharge

Photo of defective insulators and waveform of acoustic signal from insulator ring of phase 3 for two periods of the line (the signal amplitude is 120 mV).

The results in TrEasyAnalyzer.

After the repair it is usually impossible to detect the signals.