The determination of economic benefits of increasing transmission capability by dynamic line ratings is a multifaceted task. In addition, there are many parties concerned within the complex electricity markets. This paper suggests a method for the evaluation of economic feasibility and benefits, as well as for the minimum potential assessment of employing dynamic line ratings. The suggested deterministic method considers very conservative assumptions in order not to compromise the power system reliability, even though the method is intended for the power system planning and not for the operation purposes. The method is applicable for congested transmission connections between electricity market price areas and it is demonstrated with a distinct case study of congestion on the power transmission from Sweden to Finland. Despite the very conservative assumptions used in the ampacity calculation to be on the safe side, the method can clearly point out the motivation to consider the implementation of dynamic line ratings on congested transmission connections in order to relieve bottlenecks and provide benefits for the society.