A highly accurate algorithm for SF6 leakage detection

Abstract

Sulfur hexafluoride (SF6) is widely used in high‐voltage applications such as gas‐insulated switchgear (GIS) because of its excellent arc‐quenching properties. The main drawback of SF6 is that it is a strong greenhouse gas. Detecting small SF6 leakages in GIS is very important to protect the environment and to prevent the failure of aged GIS. To detect SF6 leakage, the gas pressure is measured and compensated by gas temperature. Usually, the temperature of the container surface is measured instead of the actual gas temperature. However, the temperature of the container surface is affected by ohmic heating of the internal components and by ambient temperature changes. These factors lead to a difference in temperature between the container surface and the gas inside the container, causing significant fluctuations in the compensated gas pressure. To remove such fluctuations, we have developed a computational fluid dynamics (CFD) transient model that simulates the correlation between the mean gas temperature inside the container and the container's surface temperature. The CFD simulation factors in the load current and ambient temperature to estimate the true temperature of the gas inside the container as accurately as possible. The mean gas temperature inside the container is obtained using CFD simulation and by measuring the surface temperature. The fluctuations in the compensated gas pressure were reduced from 2.4 to 0.48% by using the proposed algorithm based on pressure compensation with the mean gas temperature. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.