Impact of Rain On Transmission Lines’ Ampacity: Scotland as a Case Study

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.