The transmission losses increasing during the summer network maintenance

During the summer heats, the power system loads reach winter peaks values due to the air-conditioning. In the same time the routine network maintenance is at its culmination, respectively the network resistance is lower than the winter values. As result, during two years of experience in forecasting hourly transmission losses an increasing is detected when extreme heats are happen. In order to detect accurately losses dependence on combination between network maintenance and summer heats, statistical techniques are applied. Finally, the existing forecasting model of the transmission system operator is upgraded.