Diagnostic criteria based on the correlation of the measurement of DGA, moisture contents with PD & tan d in MV oil-filled underground cable

Abstract

Gas-in-fluid analysis refers to dissolved gas analysis (DGA). DGA facilitates the observation of the by-products of the oil degradation through its environment, the insulating and pressurizing fluid. The three main degradation processes that generate gases are thermal degradation, partial discharge and arcing. The most significant gases generated from oil decomposition are hydrogen gas (H2), methane (CH4), ethane (C2H6), ethylene (C2H4) and acetylene (C2H2) [3]. The measurements of dissolve gas (DG) were made for the medium voltage oil-filled cable. Partial discharge (PD) measurement was done the MV oil-filled cable to determine the level of PD activities. The correlation of PD magnitude and DGA level were established to determine the severity of the results and for diagnostic purposes. The measurement of moisture contents in the insulating oil was made using Karl Fisher method.