Increasing the permittivity of the propagation medium inside a hollow tube lowers its cut-off frequency, allowing it to transmit a wider range of signal frequencies. This principle is applied to the design of dielectric windows that can be used to facilitate partial discharge (PD) detection at ultra high frequency (UHF) in a HV metalclad plant such as gas-insulated substation (GIS), power transformers and circuit breakers. External UHF couplers mounted on such windows can be removed or replaced without compromising the integrity of the insulation system. By increasing the signal power level incident on a window-mounted external UHF coupler, higher sensitivity to PD can be achieved. The problem is analyzed using waveguide theory and, using GIS as an example, improvements of andap;6 dB are demonstrated by means of coupler sensitivity measurements and experiments using PD sources.
|Number of pages||5|
|Journal||IEEE Transactions on Dielectrics and Electrical Insulation|
|Publication status||Published - 2001|
- UHF measurement
- gas insulated substations
- insulation testing
- electrical insulation