Study of correlation between the parameters of dielectric absorption when diagnostics of insulation of three-core power cables by applying aggregate measurements

Three-core power cables with paper-impregnated insulation in a common metal sheath contain several layers of dielectric formed by phase and belt insulation between the cores and the sheath. When diagnosing the technical condition of the insulation of such cables according to the parameters of electrical capacity and tg δ, the problem of experimental determination of individual parameters for each of the insulation layers of the power cable arises. When evaluating the individual values of the dielectric absorption parameters of each of the insulating layers in three-wire power cables by applying aggregate measurements, the formation of a system of equations can be carried out in two different ways. In the first case, the unknown values of the capacitance and tg δ of each of the 6 insulating layers (of which 3 are formed by the insulation layers between the cores of the power cable and 3 dielectric layers between each of the cores and the sheath) are directly determined by solving a system of 6 linear algebraic equations. In the second case, the individual parameters of the dielectric are determined by minimizing the root-mean-square error of solving the redefined system of equations using the method of least squares. According to the results of the calculations, it is shown that when evaluating the uncertainties of dielectric absorption parameters using aggregate measurements, the correlations between the aggregate values can be disregarded.