Effect of detector and analyzer settings on partial discharge measurement and representation

Partial discharge (PD) measurement is usually performed with PD detector and analyzer system. The data collected during the test is generally represented as distributions. These distributions are interpreted to reveal the PD phenomenon and the state of the insulation. The paper demonstrates the effect of instrument characteristics on measurement and representation of PD phenomenon with experimental results obtained from short time PD endurance tests on oil pressboard samples. The instrumentation, a combined narrowband detector and multi-channel analyzer (MCA), is analyzed for the effect of the detector resolution and gain settings on the PD distributions. The results show the instrument dependence in the PD characteristics due to differences in measurement ability at various instrument settings. These differences in representation lead to multiple interpretation for the same phenomenon or state of the insulation and hence to wrong classification. The paper emphasis is that interpretation of the results should be made to account for the measurement ability of the instruments in use.