Improvement in the measurements of partial discharges in hydrogenerators through high-frequency grounding of couplers

In the balanced coupler technique for the detection of discharges in rotating machines, it is common practice to omit grounding the coaxial-line shielding near the couplers in order to avoid induced current loops. Recent measurements demonstrate that providing a high-frequency ground to the coaxial shielding at the capacitive couplers reduces the magnitude of the high-frequency signal propagating along the outside shield. The signal coupling between adjacent coaxial cables is thus reduced, providing a higher signal level and a better signal-to-noise ratio at the detector end