Transmission system; technical losses; prediction; software.

Losses occur on all elements of the transmission system. While they cannot be eliminated, they can be minimized. Losses can be measured or calculated using transmission line parameters. The accuracy of the calculation depends on which loss causing influences are taken into account. Among the most important external loss causing influences is the effect of the ambient temperature. The paper compares results of calculation of technical losses based only on line parameters taking into account the ambient temperature in relation to a particular transmission system using prediction software. Further, it deals with technical losses caused by a configuration change of a selected part of a transmission system related to the operation of Dlouhe Strane pumped storage hydro power plant.