Abstract
Oil-impregnated paper is widely used in power transmission equipment as a reliable insulation. However, copper sulphide deposition on oil-paper insulation can lead to insulation failures in power transformers. This paper presents the influences of copper sulfur corrosion and copper sulphide deposition on copper wires and oil-paper insulation in power transformers. Thermal aging tests of paper-wrapped copper wires and bare copper wires in insulating oil were carried out at 130 °C and 150 °C in laboratory. The corrosive characteristics of paper-wrapped copper wires and bare copper wires were analyzed. Dielectric properties of insulation paper and insulating oil were also analyzed at different stages of the thermal aging tests using a broadband dielectric spectrometer. Experiments and analysis results show that copper sulfide deposition on surfaces of copper wires and insulation paper changes the surface structures of copper wires and insulation paper. Copper sulfur corrosion changes the dielectric properties of oil-paper insulation, and the copper sulfide deposition greatly reduces the electrical breakdown strength of oil-paper insulation. Metal passivator is capable of preventing copper wires from sulfur corrosion. The experimental results are helpful for investigations for fault diagnosis of internal insulation in power transformers.
Highlights
Oil-paper insulation plays an important role of the internal insulation of power transformers
This paper presents the influences of copper sulfur corrosion on copper wires and oil-paper insulation in power transformers
This paper presents the influences of copper sulfur corrosion and copper sulphide deposition on copper wires and oil-paper insulation in power transformers
Summary
Oil-paper insulation plays an important role of the internal insulation of power transformers. Aging of transformer insulation is a gradual procedure which can eventually threaten the safe operation of power transformers [1,2,3,4]. During long-term operation of power transformers, oil-paper insulation is exposed to multiple stresses, including electrical, thermal, and mechanical factors. Corrosive sulfur is a factor that influences aging of oil-paper insulation, when it is dissolved in insulating oil. An approach to test corrosive sulfur in transformer oil was first proposed in [5]. Failures resulting from corrosive sulfur in transformers and reactors have happened frequently and raised the attention of researchers and engineers again [6].
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