EVALUATION CRITERIA OF INSTALLED TRANSFORMER POWER AT DISTRIBUTION SUBSTATIONS OF ELECTRICAL NETWORKS

Abstract

This work is devoted to approaches to determining and substantiating the optimal power value of transformers that installed at distribution substations. During the selection of the transformer under working the electrical load schedule of consumers of distribution substation in the power grid, it is necessary to ensure in full using of every unit of installed transformer capacity. For example, there are three transformers that belongs to the 10 kV, 35 kV and 110 kV voltage levels. It is shown the calculation of the optimal value of the transformer power and the selection of this power is performed, based on the nomenclature of transformers. It was carried out a technical and economic comparison of possible combinations in number and capacity of transformers to set the optimal power level.
 Active energy losses, profit from the transporting of active energy and the total discounted costs function are the estimation of the installed transformer capacity. The transformers chosen for installation at the substation of the power grid are estimated for the ability to work at the highest ambient temperature level of +40°С, based on the temperature of the hot-spot point on the surface of the insulation of the windings.
 This work ends by conclusion in comparison of the results of two approaches to estimating the lifetime and residual operation life - when the hot-spot point is in stationary and when it moves during electric load changes.