To decrease and remove of many noises that are detected in PD (partial discharge) measuring test, we forced on detection of those. We made W-LC filter for measuring PD, which adapted that to field test. We tested after design laboratory circumstances like field line, and then the phase change properties of detected signal in UHF sensor were measured by Lemke probe and oscilloscope (TDS-3054, Tektronix). Eventually we checked decrement of noises from experimental result. Also from experimental result at the joint box of 22.9 kV distribution line, we obtained good data which enable noises to decrease. Hereafter those results will be adapted at ultra-high voltage for trouble prevention and on-line cable watch, diagnosis of those