Yoshihide Aoshima

Influence of Humidity on Lightning and Switching Impulse Flashover Voltages

A long run flashover test was carried out from 1967 to 1969 to investigate the effect of atmospheric humidity on lightning and switching 50-percent flashover voltages of air gaps and suspension insulators. From the test results, it was found that the influence of humidity on flashover voltages of air gaps varied greatly from their flashover voltage-gap length characteristics.

Influence of Air Density on Flashover Voltages of Air Gaps and Insulators

Flashover tests were conducted with the cooperation of the Central Research Institute of Electric Power Industry, the Tokyo Electric Power Company, Inc., and the Chubu Electric Power Company, Inc., at the top of Mount Ny?gasa, 1850 meters above sea level and the Takeyama Laboratory, nearly at sea level, to obtain comparative data to evaluate the influence of air density on the flashover voltages of air gaps and insulators.

Influence of Switching Impulse Wave Shape on Flashover Voltages of Air Gaps

Flashover tests were conducted by using three kinds of positive polarity switching impulses, exponential, damped oscillatory and linearly rising impulses. The influence of switching impulse wave shape on the flashover characteristics of air gaps was investigated and the basic data were obtained concerning the minimum 50-percent flashover oltage of air gaps and the time to crest of these switching impulses.

A High Quality Voltage Divider Using Optoelectronics for Impulse Voltage Measurements

By applying an optical measuring system, which consist of light emitting diode, optical fiber light guide and photomultiplier, a high quality shielded resistance divider for impulse voltage measurements, whose response time is less than 5 ns, has been obtained. The characteristics have been verified experimentally.

Impulse Flashover Characteristics of Long Air Gaps and Atmospheric Correction

The flashover voltages of long air gaps such as rod-rod and rod-plane gaps vary with impulse waveform, polarity, gap spacing and atmospheric conditions.

Development of a high voltage universal divider

A new high quality universal voltage divider was developed as a result of theoretical and experimental investigations. Various kinds of tests have been carried out on the divider in order to confirm its performance. The results show that the divider has a response time of about 10 ns and is capable of measuring voltage of various waveforms accurately from lightning impulse to dc voltage.

Resistor Divider with Dividing Element on High Votage Side for Impulse Voltage Measurements

The response characteristics of a resistor divider with dividing element on high voltage side were investigated theoretically and experimentally. As the results, it was revealed that it could be realized a divider having an excellent response characteristic by this method.

DC Voltage Distribution Characteristics on Polluted Insulator String

Equipment for measuring the DC voltage distribution on polluted insulator strings was manufactured, utilizing opto-electronic techniques, and voltage distribution characteristics were measured through artificial pollution tests

A consideration on measurement of voltage callapse during chopping in chopped impulse test of transformer

In the chopped impulse test of a transformer, a steep voltage collapse appears across the terminals of the transformer to be tested. This paper clarifies the wave shape of the voltage collapse during chopping and the requirements of a device for measuring the voltage collapse.