Consideration of Active Resistances Temperature Dependency of Power Transformers when Calculating Power Losses in Grids

An analytical method for calculating power losses is developed taking into account the temperature dependence of the active resistances in power transformers. The proposed mathematical model is based on the transformation of the nonlinear function of the power loss versus linear dependence. This transformation is based on the integral least-squares method. For the power transformer TMN 6300/35, the power losses are calculated taking into account the temperature dependence of the load losses. The results of comparison of power losses in transformers with power losses in power transmission lines show the need to take into account the temperature dependence of the resistance in transformers.

I. Introduction

Increasing the accuracy of calculations of losses of electric energy requires taking into account the temperature dependence of the active resistance of power transmission lines. At the article [1] the thermal calculation of an isolated wire is given in the steady state regime. The authors in [2] presented a mathematical model of a 4-wire system in insulated wires, which allows to determine the temperature of wires taking into account the mutual influence of the wire of each phase. The described thermal model of the stationary regime of an insulated wire in [3] allows to calculate the temperature of both insulated and bare conductors. At [4], individual aspects of the effect of insulation on thermal processes in the wires of overhead transmission lines were investigated. The simplified model proposed by the authors of [5] for calculating the temperature of power transmission lines in non-stationary modes allows one to determine the temperature by an analytical method. This mathematical model makes it possible to simplify the calculation of nonstationary modes of power transmission lines. The proposed electro-thermal model was used by the authors of [6] to monitor the temperature in power transmission lines in stationary and non-stationary modes. The influence of the current in the conductor and the weather conditions on the resistance of the conductor was separately analyzed in [7]. This analysis makes it possible to distinguish the effect of each component of the heat balance equation on the conductor temperature.