A case study on alleviating electric transmission congestion using dynamic thermal rating methodology

Electric transmission congestion has always been a longstanding concern faced by Power System Operators of Pakistan (PSOP) due to uncontrollable power demand growth and outdated electric transmission infrastructure. For this reason, reliable and economic power supply is being frequently interrupted in order to relieve congestion even when adequate power supply is available. A possible solution is upgrading and expanding transmission lines by reconducting old lines, or, through construction of new ones. But the huge economic investment and the suffocating national economy are putting serious hurdles for such infrastructure improvement. More importantly, only infrastructure improvement is not a solution because of the exponential demand growth and the increasing need for power utilization from cheap energy sites and renewable energy sources. Hence, there is an urgent need for smart transmission systems that can monitor controlling factors (i.e. weather parameters and conductor thermal condition) in real time and estimate maximum allowable current carrying capacity (or ampacity) for optimal utilization. This paper presents an alternative solution based on Dynamic Thermal Rating (DTR) to alleviate electric transmission congestion and to keep power system intact especially in contingencies. The detailed assessment of Power System of Pakistan (PSP) reveals conservative and static approaches employed in rating overhead transmission lines and fixing protection equipment's settings. As a case study, 132KV transmission line in Lahore region of Pakistan was chosen keeping in view meteorological data availability and prevailing overloading issue in the area. The analysis discovers that smart adaptations based upon varying weather conditions, like ambient temperature, wind speeds, wind direction, solar radiations as well as adjustable conductor temperature, provide a feasible scenario for dynamic rating of transmission lines. Aggregating all supposed conditions, additional line's capacity can be increased up by 38.15% and 51.34% on average for day and night time respectively.