Comparison of Substation Uprating Techniques Using a Novel Graphical Method Based on System Planning Constraints

This paper presents a comparison of different fault-current mitigation techniques used for adding an extra transformer to an existing substation whose fault-current level is close to nominal. Emphasis is placed on evaluating the net increase in substation loading capability provided by each technique while taking into account apparatus and system planning constraints. Operation under unusual peak loading conditions is investigated in terms of maximizing the use of substation assets. A graphical method based on linear programming is introduced to simplify the comparison of the techniques studied based on conventional passive technologies. The main strengths of the method are its ability to assess all techniques with a single general formulation and its possible generalization to complex problems. This paper shows that the avoided cost for reconfiguring a network and balancing the loads on the substation transformers could potentially justify more expensive techniques.