The economics of power transmission requires operators to maximise the power through the network. Increasing knowledge of the impact of environmental factors on the current carrying capabilities of bare wire overhead lines is, therefore, important. Cost savings resulting from enhancing thermal transfer capabilities of transmission lines has motivated many utilities and power systems research centres to investigate techniques for maximising operational parameters. Enhancing power ratings of bare power conductors brings, alongside improved generated power dispatch flexibility, cost savings and economical and technical challenges. The aim of this paper is to examine some of the existing techniques employed to compute the ampacity of bare power lines and discuss practical limitations of these techniques. In addition, the impact of each technique will be considered from an operational prospective. On-line and off-line techniques are summarised and compared based on the nature and quality of power sources connected to the system, e.g. power output of windfarms tends to be of intermittent nature. Index Terms-Ampacity of bare power lines, dynamic thermal ratings, generation dispatch, ruling span of transmission line and thermal time constant.

The worldwide fast pace at which wind power generation technology and its drive train is growing has increased the demand for wind farm connection into the power grid. The UK target of increasing wind energy contribution coupled with the excellent wind profile has led to growing demand for distribution and transmission connection points. The main obstacle hindering large scale of integration of the wind energy is the thermal capacity limits of the existing transmission lines infra structure. Thermal capacity computation techniques are based on heat balance equation stipulated in IEEE 738. This paper analyses the heat balance equation and proposes the addition of new variable to the set of heat balance equations, discusses the economic aspects of dynamic line ratings. The main objective of this paper is to mathematically integrate the effect of precipitation rate into the heat balance equation, based on empirical study conducted. Index Terms-Ampacity of bare power lines, dynamic ratings, ruling span of transmission line, temperature overshoot effect and thermal time constant. I.

The increase in volume of embedded generation, particularly wind farms in the United Kingdom coupled with change in nature of connected load (growing number of electric vehicles and domestic PV) will require system operators to look for ways to reduce network constraints. Increasing the current carrying capacities of transmission lines while ensuring that safety margins are not encroached will result in significant improvements to overall transmission efficiency and reduction in operational costs. It is possible to increase transmission lines transfer capacities through monitoring of conductor temperature in real time; however, there are conditions that will necessitate limitations. One of these is the effect of conductor shading (due to trees for example), another is the temperature overshoot effect (mainly relevant to new conductors running at 90° Celsius). This paper will focus on studying the cooling effect of rain on conductor ampacity. A close relationship (rain Vs conductor temperature) often ignored in studies concerned with ampacity measurements and computation. Index Terms-Ampacity of bare power lines, dynamic thermal ratings, generation dispatch, ruling span of transmission line, temperature overshoot effect and thermal time constant. I.