Hideo Tsukioka

Suppression of static electrification of insulating oil for large power transformers

Streaming electrification in transformers occurs at the interface between the insulating oil and the insulating material as the oil circulates in the transformer. As a result, the insulating oil and the surface of the solid materials become charged and dielectric breakdown is possible within the oil or at the interface of insulating materials.

Niew Apparatus for Detecting Transformer Faults

A diagnostic apparatus for detecting gases dissolved in transformer oil is described, in which a tetrafluoroethylene-perfluoroalkylvinylether copolymer membrane is used to separate H2 CO, CH4, C2H2, C2H4, and C2H6 from the oil. These gases are detected with a new gas detector, which consists of a catalytic gas sensor and a gas chromatograph using air as the carrier gas. Using the gas concentration, the apparatus automatically determines whether a transformer is operating normally or not and, in the latter case, what kind of fault may have occurred. By the above diagnostic apparatus, a transformer could be diagnosed simply and inexpensively. This apparatus should prove useful for identifying what kind of fault may have occurred.

New Apparatus for Detecting H2, CO, and CH4 Dissolved in Transformer Oil

This report presents a new method of separating H2, CO, CH4, C2H2, C2H4, and C2H6 dissolved in transformer oil and detecting H2, CO, and CH4, in which a tetrafluoroethylene-perfluoroalkylvinylether copolymer membrane is used to separate gases from the oil. The quantities of H2, CO, and CH4 that permeated through the membrane were relatively large. These gases were detected with a new gas detector, which consists of a catalytic gas sensor and a gas chromatograph, and which uses air as the carrier gas. Compared with conventional methods of gas analysis, H2, CO, and CH4 dissolved in transformer oil can be analyzed simply and inexpensively with this method. As a result, this new method should prove useful in determining whether a transformer is operating normally or not.

Development of low-permittivity pressboard and its evaluation for insulation of oil-immersed EHV power transformers

The development of a low-permittivity pressboard obtained by blending polymethylpentene fiber with cellulose fiber is described. The permittivity is 3.5, which is lower than that of conventional pressboard. With this pressboard, insulating characteristics of intercoil models were investigated under lightning impulse and AC voltage conditions. It is demonstrated that a spacer fabricated from this pressboard material increases the partial discharge inception and breakdown voltages up to 30% compared with conventional pressboard spacers. >

Apparatus for Continuously Monitoring Hydrogen Gas Dissolved in Transformer Oil

This report presents an apparatus for continuously monitoring of hydrogen gas dissolved in transformer oil, in which a polyimide membrane is used to separate the hydrogen from the oil. The hydrogen is allowed to permeate through the membrane and contact a gas sensor every 72 hours. The characteristics of the permeation of the hydrogen gas through the polyimide membrane and of the detection of the hydrogen gas by the gas sensor are described under various conditions. Problems encountered when the apparatus is installed on a tran are also studied and solved. As a result, this new apparatus was found useful in determining whether a transformer is operating normally or not.

Development of low dielectric constant pressboard

High breakdown strengths of oil-impregnated insulating materials are expected and the insulating design is improved if the dielectric constant of cellulose material is close to that of insulating oil. This paper presents a low dielectric constant pressboard which can be obtained by blending polymethylpentene fibre with cellulose fibre. The dielectric constant is 3.5, which is a very low value compared with the 4.7 of conventional pressboard. By using the new pressboard, decreased insulating distances and smaller transformer sizes are expected.

Developmetn of transformer insulation utilizing new low-permitivity pressboards

A pressboard providing both low permittivity and good mechanical properties is required as for insulating material in oil-immersed transformers insulation. Using a newly developed pressboard, insulation characteristics of intercoil models are investigated under lightning impulses and AC voltage conditions. it is demonstrated that a spacer fabricated from the new pressboard material (permittivity of 3.5) increases the partial discharge inception and breakdown voltages up to 30%, compared with those of conventional pressboard spacers (permittivity of 4.7).