Akinobu Miyazaki

Partial discharge measurement in a long distance SF/sub 6/ gas insulated transmission line (GIL)

We evaluated the generation, radiation, and propagation characteristics of partial discharge (PD) signals in 275 kV full-scale SF/sub 6/ gas insulated transmission line (GIL) model with a length of 168 m. We analyzed the correlation between the PD current pulse and the radiating electromagnetic wave by comparing their frequency spectrums. In addition, simultaneous measurement was performed on the current pulse waveform of a single PD and the corresponding electromagnetic wave as propagated in GIL, with the phase gate control method. As a result, the PD signal attenuation rate of 50 MHz and 300 MHz for the propagation of 100 m was obtained as 2.5 dB and 8.7 dB, respectively. Furthermore, by selecting an appropriate measuring frequency, even a 1/spl sim/2 pC PD could be detected at the measuring site 168 m away from the PD source in the GIL.

Line constant measurements and loading current test in long-distance 275 kV GIL

This paper reports on the results of a loading current test and measurements of the line constants of a long-distance gas-insulated transmission line (GIL) in a tunnel. The loading current test was carried out at 80% rated current, to verify the soundness of the thermal expansion and contraction of the GIL. As a result, the performance of the GIL was confirmed to be appropriate in terms of the thermal expansion and contraction. With respect to the line constants and transient enclosure voltage, each of the measured values was found to be at an appropriate level presenting no problem for the service operation of this line.

Gas pressure monitoring system for GIL using fiber-optic gas density sensors

The authors have developed a fiber-optic gas pressure monitoring system with new gas density sensors for detecting the leakage of insulation gas of gas-insulated transmission lines (GILs). In this system, the gas pressure of over one hundred gas compartments can be monitored with several optical fibers and without electric power supply to the sensors. This simple and highly reliable system enables speedy gas leakage detection, allowing one to take appropriate measures before reaching its critical pressure. The developed sensor makes a mechanical bend of an optical fiber when there is gas leakage, and causes optical transmission loss as the detected signal. Using a conventional optical time domain reflectometer with these sensors, a multi-point sensing system can be constructed. In this paper, the authors report the principle of this sensor and the design of the monitoring system for Japans Shinmeika-Tokai GIL.

Long-distance 275-kV GIL monitoring system using fiber-optic technology

This paper reports the monitoring system applied for a long-distance 275 kV gas-insulated transmission line (GIL) using the latest fiberoptic technology. The monitoring system consists of two major parts. One monitors the GIL itself, for example, the insulated gas pressure and the surface temperature of the GIL enclosure, fault localization, and so on. The other monitors the condition of the tunnel where the GIL is installed. To construct a simpler and more reliable system, we have developed and applied certain kinds of optical sensors and measuring equipment. This system was verified to be effective through a loading test on an actual GIL and a high voltage test, etc. and has been put into actual operation service since February 1998.

Results of Partial Discharge Measurements in a Long-Distance 275 kV GIL

In this paper we introduce a newly developed measuring system for partial discharges (PD) in after-laying tests on site for a long-distance gas insulated transmission line (GIL) in a tunnel. We evaluate the length of harmful particles for the overvoltages to be considered for the Shinmeika-Tokai GIL. The length ofparticles detectable by the PD sensors is compared with the length of harmful particles. The highly sensitive PD measuring system took advantage of low noise levels in the tunnel. We applied the system to the after-laying test on site and confirmed that the developed system was effective to verify the required performance of a long distance GIL in a tunnel.