- 期刊
變電所氣封開關設備外殼雜散電流與開關突波探討
Study on Stray Current and Switching Surge of GIS Enclosure of Substations
摘要
大環境變遷與因應高科技產業快速發展，為提高供電品質，高壓輸電線路之規劃設計已逐漸由架空方式轉變為地下化；同時採用氣封開關設備（GIS, Gas Insulated Switchgear）之室內變電所設計方式日益普及，逐漸取代傳統屋外型變電所。由於電力系統開關操作時，GIS金屬外殼易發生感應暫態過電壓，與其他設備具電位差時（如電纜遮蔽層），極易造成過電壓火花放電，成為對電力品質一潛在影響因素。GIS金屬外殼分成數段，各段GIS內的相導體對外殼有分佈電容存在。為避免造成環流，支持鐵架與避雷器接地線分別單獨接至共同接地匯流排。因此兩端電壓差即可能造成環流及暫態電壓之火花放電。本文以台電公司之345kV GIS為研究對象，除模擬雜散電流外，同時探討斷路器投入時對GIS外殼感應電壓影響；文中利用ATP-EMTP電磁暫態軟體進行模擬。透過實測及模擬，本文發現利用GIS外殼三相短接後再接地方式，可有效降低金屬外殼間雜散電流；此外，若GIS斷路器三相接點投入不同步，可能在GIS外殼與電纜金具間產生數百kV之暫態電壓，可採加裝突波抑制元件方式，避免火花放電。
並列摘要
Owing to the change of living environment and rapid growth of Hi-Tech industry, the power transmission systems are gradually designed as the underground type instead of overhead type for better power quality. The gas-insulated switchgear (GIS) is widely employed for the indoor-type substations. When the switching operations are performed, the transient voltage occurred on the enclosure of GIS. This transient voltage may lead to flashover between the junctions with different voltage (like sheath layer of power cables). The phenomenon of flashover will result to the danger of crews and the influence of the power quality. GIS is composed of several segments of metal compartment, the capacitance exists between the phase conductor and enclosure. To reduce the induced loop current, the grounding of supporting shelf and sheath layer of power cable are connected to ground network independently. In this paper, based on the Taiwan Power Company 345 kV GIS substation, the stray current and switching transient voltage of the enclosures of GIS are studied. The ATP-EMTP software package is used for simulations. In this paper, it is found that by bonding three phase enclosures together and connected to the ground network, the induced loop currents can be mitigated effectively. In the meanwhile, transient voltage of several kilo volts will occur for the asynchronous switching action of three phase contacts of circuit breakers. The surge voltage limiter (SVL) can be adopted to avoid the flashover caused by the switching transient voltage.