M. Honda

Impulse Voltage Field Emission Characteristics and Breakdown Dependency Upon Field Strength in Vacuum Gaps

High voltage impulses were used to investigate various possible factors influencing the prebreakdown current and breakdown in vacuum gaps of sphere-to- sphere and rod-to-plane.

Breakdown Characteristics of Moving Transformer Oil

As a result of investigating breakdown characteristics of moving oil, it has become clear that the breakdown voltage of ac and dc for moving oil is higher than that for stationary oil by 10-15 % at a moving velocity of 5 cm/s region; the former voltage becomes almost equal to the latter voltage in the region of 25 cm/s, and the former is reduced to lower than 90 % of the latter when the moving velocity exceeds 100 cm/s. However, for impulse voltage, the breakdown voltage of moving oil is the same as that of stationary oil.

Partial Discharge Automatic Monitor for Oil-Filled Power Transformer

This paper describes a new type of partial discharge (PD) automatic monitor capable of detecting possible troubles caused by PD inside a transformer in the field and preventing the unfavorable phenomenon from expanding.

V-T Characteristics of Epoxy Mold Insulation for Sustained AC Voltage

This paper describes experiments conducted to determine the cause of epoxy mold insulation breakdown under sustained applied AC voltage. It can be readily understood that epoxy mold insulation, widely used as solid insulation in gas-insulated switchgear, is subject to breakdown under sustained applied voltage when the mold insulation contains large voids. However, epoxy mold insulation which is practically void-free also deteriorates under sustained applied voltage. It has been clarified by conducting experiments using various embedded electrode materials that the deterioration of this void-free epoxy mold insulation is primarily caused by an electric field concentration due to micro-protrusions on the embedded electrode surface and a small partial discharge which occurred at minute debonded portions around the micro-protrusions.

Life Performance of Zinc-Oxide Elements Under DC Voltage

The voltage-current, watt loss, and characteristics of three kinds of ZnO elements were compared when subjected to ac and dc voltages.

Local Voltage Oscillation in Interleaved Transformer Windings

In this paper, local voltage oscillation of each turn within sections of interleaved transformer winding are discussed. Because of interlacing of turns, each turn within a pair of sections of the winding has initial voltage distributions quite different from final voltage distributions. This difference brings about local oscillation when a steep impulse voltage enters the winding.

Problems of Long-Term Reliability for UHV Transformer Insulation

Through long-term (3 years) partial discharge (PD) tests on some component models for transformer insulation, the authors have revealed that transformer insulation has a threshold voltage, Vol below which no partial discharge will occur regardless of how long the voltage may last. The value of VO is more than 62.5 percent of a 50-percent probability PD inception voltage at one-minute ac test.

HVDC Breakdown of Transformer Oil and the Effect of Space Charge on it

Experiments have been conducted on high voltage dc breakdown characteristics with large oil gaps of typical electrode setups, which are plane to plane and cylinder to plane. These have been confirmed in a voltage-range up to 800 kV and in gap length up to 307 mm.

DETERIORATION OF EPOXY MOLD INSULATIONS DUE TO VOLTAGE ENDURANCE

ABSTRACT This paper describes experiments to determine the cause of epoxy mold insulation breakdown under sustained applied voltage. It can be readily understood that epoxy mold insulations, which are widely used as solid insulation in gas insulated switchgear, break down under sustained applied voltage when the mold insulations contain significantly large voids. The working electrical life of such insulations can be expressed as a gradient plotted against sustained applied voltage. However, epoxy mold insulations which are practically void-free also deteriorate under sustained applied voltage. The experiments described in this paper show that the deterioration is caused by small discharges occurring in the minute space at the embedded electrode/epoxy resin interface.

Testing Facilities for Developing UHV Equipments

The testing facilities of UHV (Ultra High Voltage) laboratory are described in this paper. The voltage rating of testing facilities and dimensions of the laboratory for developing UHV substation equipments, especially transformers and gas insulated equipments, are discussed on the basis of research and development experiencies of UHV equipment manufacture.