Condition assessment model for GIS operating under tropical conditions

Gas Insulated Switchgear (GIS) has been in use in transmission system for more than 30 years with good reliability. However, in our case study of 631 CB-bays of GIS operating under tropical conditions, we observed failure rates over twice the value reported in the 3^rd CIGRE's survey of 2007. Following this observation, it becomes practically important to develop a condition assessment model for GIS operating under tropical conditions. As a part of this process, knowledge rules for humidity content in SF6 insulation were investigated through the experiment inside the HV Laboratory in TU Delft with a solid-and-gas insulation setup with AC voltage stress. The controlled parameter used in the experiments were resembling the actual condition in tropics. In this paper, the condition assessment model for GIS is proposed. To support the model, different diagnostics to assess the critical components of GIS operating under tropical conditions are discussed. Following that, an example of knowledge rules to interpret the outcome from the diagnostics is also given.