Development of a high‐pressure air‐insulated 72/84‐kV disconnecting switch corresponding to bus‐transfer current switching

Abstract

SUMMARYSF 6 gas has excellent dielectric strength and current interruption performance. For these reasons, it has been widely used for gas-insulated switchgear (GIS). Today, such global environmental problems as global warming are important issues of concern. SF 6 gas is known as a greenhouse gas with a long atmospheric lifetime, and has global warming potential of 23,900. SF 6 -free 72-kV GIS was recently developed by using high-pressure air and a gas/solid hybrid structure. But an alternating current disconnecting switch (DS) has yet to be developed thus making this type of SF 6 -free 72-kV GIS unsuitable for double bus-bar application. Consequently, the development of a high-pressure air-insulated DS corresponding to bus-transfer current switching has been expected. The bus-transfer current is the highest among all current interruption requirements for the DS. To develop an alternating current DS, efforts must be made to reduce arcing damage to the electrode. This paper describes the fundamental characteristics of current interruption in the plain break type and the magnetic field driven type. Then, average arcing time of the magnetic field driven type was estimated by magnetic flux density. Finally, two types of DS, which were a high-speed plain break and a low-speed magnetic field driven, were confirmed to comply with bus-transfer current switching requirements on JEC standard.

Development of SF6 Gas‐Insulated Disconnecting Switch with Spiral Electrodes Using Motor Operating Mechanism

“…Figure 10 shows the variation in the arcing time for repeated current interruption when using a real type B electrode. The arcing time is 40 ms at a maximum, and the average arcing time is approximately 19 ms. Based on past test results [5], the average arcing time for 200 interruptions in a disconnecting switch that satisfies the loop current interruption requirement is 5 to 60 ms. Their values are confirmed to be within this range in the magnetically driven disconnecting switch described in this paper.…”

“…GIS in recent years has been reduced to about 40% of the installation surface area compared to the 1970s [1], and research on lowering the oper-ating force while reducing weight and size continues [2,3]. However, a method of reducing the arc time without increasing the acting force or contact parting speed so as to reduce device size and increase reliability is preferable [5]. In the JEC ratings [4], the voltages are as follows: 300 V between electrodes in a substation with a bus length more than 100 m longer than the loop route length, and 100 V between electrodes when the length is less than 100 m. The current must be taken into consideration up to the rated current values.…”

“…To reduce the arc time, in present-day disconnecting switches for loop current interruption the contact parting speed has been increased to about 1.0 m/s by using spring-action devices. However, a method of reducing the arc time without increasing the acting force or contact parting speed so as to reduce device size and increase reliability is preferable [5]. Thus, development of disconnecting switches that satisfy the need for loop current interruption by using a motor-operated method is under way [6].…”