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ULTRASONIC METHOD FOR TESTING OF POWER TRANSFORMERS

Danijel Brezak ; Končar - Electrical Engineering Institute Inc.
Dalibor Filipović-Grčić ; Končar - Electrical Engineering Institute Inc.

Sažetak

Ultrasonic method of detecting PD is based on the fact that the electrical energy of the PD
transforms in a mechanical energy, an ultrasonic acoustic wave that spreads through the transformer to
the tank wall. From time difference of wave detection on different sensors, a possible location of the
source can be estimated. Ultrasonic method can detect other transformer deficiencies such as loose
contacts and local overheating of oil (T>200°C).
Three case studies are given in this paper. The first case was where DGA indicates the thermal
problem in the oil and the result of ultrasonic testing points at OLTC contacts. In the second case an
ultrasonic method was performed after electrical method detected high levels of PD at voltages much
lower than the nominal. Ultrasonic method detected non-grounded parts of the returning limb electrostatic
screen. In the third case, a failure of transformer, namely a breakdown from the HV bushing end shield,
initiated a series of tests on similar transformers installed at the same substation. The assumption was
that PD occurred in the shied epoxy insulation and eventually caused the breakdown.

Ključne riječi

diagnostics; power transformer; partial discharges; ultrasound; acoustic emission

Hrčak ID:

199220

URI

https://hrcak.srce.hr/199220

Datum izdavanja:

15.8.2017.

Posjeta: 740 *