HILBERT CURVE FRACTAL ANTENNA FOR DETECTION AND ON-LINE MONITORING OF PARTIAL DISCHARGES IN POWER TRANSFORMERS

This article describes the design of UHF Hilbert curve fractal antenna (HCFA) specially adapted for the partial discharge monitoring system. The authors present the mathematical apparatus for calculating resonant frequencies of Hilbert fractal antenna and results of a computer simulation of the developed prototype. In the design process, the antenna's working environment (mineral oil) and the mechanical construction of the transformer inspection window were taken into consideration as well. The article also shows the results of laboratory tests carried out in the transformer tank model with different type of partial discharge sources. Both simulations and partial discharge measurements showed that the HCFA, due to such properties as: multi-resonance, small size, low fabrication cost and high sensitivity, is an interesting alternative to other UHF probes installed in transformer inspection window.