RF PD signal propagation in GIS: Comparing S-parameter measurements with an RF transmission model for a short section of GIS

This paper describes work done recently to characterize and better understand propagation of PD signals in the VHF and UHF bands in GIS. While carrying out a routine CIGRE TF 15/33.03.05 UHF PD Sensitivity Verification Step 1 Laboratory Test procedure, RF transmission measurements were made on the same GIS set-up employed for the CIGRE test, using an RF vector network analyzer. In addition, a comprehensive 3-D RF field simulation model of the set-up was created, based on the detailed design drawings of the GIS. The transmission measurements were simulated in the RF model and the results compared with the actual measurement data. This shows once again the extreme complexity of GIS as an RF signal propagation environment, the difficulty describing a transfer function or in extracting useful meaning from such measurements, set against the relative simplicity of the CIGRE procedure for establishing measurement sensitivity and guidelines for sensor placement.