Assessment of efficiency and condition based optimum loading of transmission lines

Abstract

Transmission lines in any transmission network is the critical part or the one of the major limiting factors for power transfer capability of the transmission network. The thermal power transfer capability of Overhead Transmission lines is primarily a function of the height of the conductor above the ground. This height affects the safety of the public and is therefore clearly specified in legislation. Different methods for determination of Power Transfer capability of transmission lines are available. These include deterministic and various probabilistic approaches. The latter include a model simulating condition that affect the safety of the transmission line relating specially to the conductor position from which a measure of safety is developed. This measure can be used by designers to optimally design the transmission line from current loading point of view. The deterministic approach has been used by most utilities around the world, as it is quick and simple. That method assumes bad cooling conditions that will result in the line design temperature being achieved. Probabilistic methods use actual weather data and conditions prevailing on the line to determine the likelihood or probability of a certain condition. In this project, condition was taken as the conductor temperature rising up to the design temperature, which is 75 degree Celsius. Designing of transmission lines in Sri Lanka has been done considering average weather conditions through out the year. Whereas in the real situation, weather conditions are seasonally varying. Therefore, based on the seasonal variation of weather condition in Sri Lanka, existing transmission network can be optimally loaded delaying future construction of transmission lines