Application of modern diagnostic techniques to assess the condition of oil and pressboard

Aging of oil-paper insulation was investigated under controlled laboratory conditions. Traditional and modern diagnostic tools and techniques are discussed. Insulation condition testing includes common chemical diagnostics such as acidity tests and several new chemical techniques such as determination of relative content of dissolved decay products by spectrophotometry, solid suspension by turbidimetry, Fourier transform infrared spectroscopy, and electrical diagnostic techniques that have gained exceptional importance for utility professionals, such as polarisation/depolarisation current and frequency domain dielectric spectroscopy measurements. Based on the preliminary results, the suitability of each method analyzed along with its interpretation scheme. Finally, recommendations for further investigation are presented.