Detection of partial discharge caused by repetitive voltage pulses using high frequency current transformers
Maurizio Zajadatz, Lucas Braun, Jonas Reiter, Laura Hörmann, Michael Suriyah, Sebastian Coenen, Thomas Leibfried · IET conference proceedings. · 2024
In the evaluation of insulation systems, partial discharge (PD) diagnostics have proven to be a recognized means of nondestructive testing. Normally, PD is expected at high voltage equipment. However, high electrical field strengths also occur in low-voltage equipment like low-voltage motors and consequently PD occur, especially in low-voltage machines that are subjected to pulsed voltages. In order to be able to differentiate these PD pulses from interference caused by a voltage pulse with fast rising edge, measurements in the range of triple-digit MHz have to be considered. In this work it is shown that PD in the high frequency range can be measured on twisted pair devices under test (DUTs) as well as on real motor windings of a 3 kW asynchronous machine. It was irrelevant whether the DUTs were stressed with sinusoidal voltages or repetitive steep-edged test voltages. The repetitive test voltage is generated by a 3-Level Neutral Point Clamped (3L-NPC) inverter. Measurement results are given on the sensitivity of the measurement method and the location of the PD occurring on the test samples were investigated.