Investigation of UHF Probe Performance for Partial Discharge Detection in Power Transformers

Recently, UHF partial discharge (PD) detection on power transformers attracts lots of attentions. For the transformers already installed in power network, the UHF signals can be captured only by UHF probes installed through oil drain valve. Although UHF probes are commercially produced, there are a lot of missing information on characteristics and features of these probes for PD detection. In this paper, a detailed study on characteristics of UHF probe including proper detection frequency range, radiation pattern, polarization, influence of position of probe and insertion depth of probe on captured PD signals is presented using an exhaustive laboratory measurements and electromagnetic simulation works. Most of parameters are introduced for the first time in application of UHF PD detection in power transformers. After providing UHF probe characteristics, optimize situation of each parameter is presented. Using the information given in this paper, prevents incorrect detection and analyzing of PD and wrong decision about insulation status of power transformer