Radio interference and transient field from gas-insulated substations

Gas-insulated substations (GIS), owing to their compact nature, offer an attractive alternative to conventional substations in areas where space is limited such as in urban areas. Consequently, it is important to address the issue of environmental conditions within the substation and in the surrounding areas. This paper reports the results of radio interference (RI) and transient field measurements at two GIS in Ontario, Canada. For comparison with RI levels taken at the GIS, RI levels outside two hospitals in the Toronto area were also measured. The transient field study covers electromagnetic interference (EMI) levels generated during switching operations, and includes measurements inside and outside the GIS. Measurements show that RI levels from the GIS were either below background levels, or contributed little to the background. RI levels outside the GIS and the hospitals were similar. Peak transient field values up to 580 V/m were measured inside the station building, and dropped to background values of 10 V/m at about 120 m from the station. The transient field (E) dropped off at a rate of 3/2 power with distance (d) from the air-insulated 115 kV bus, i.e. E∝d^-1.5