Tabu Search-based optimal choice of lines for voltage derating in lightly loaded, high voltage constrained networks

Abstract: In power system planning, the general concern is the ability of a power system to supply increasing loads without undervoltages. Nonetheless, decrease in loads can also occur in power systems, e.g., when mines are decommissioned leading to shrinkage in load. Depending on the scale of the load reduction, problem of steady overvoltages can arise. This study proposes an investigation of using of step-down transformers to reduce steady state overvoltages in a lightly loaded network comprising of long corridors. The investigation evaluates the proposal of installing transformers at both ends of the length network, forming a ring of transformers to derate the operating voltage of the derated network. The load flow simulation studies are initially carried out manually by scaling the load down using the Power System Software for Engineers (PSS/E). The load flow studies for the lowest load served without violations are carried out for the case without transformers and the derated case with transformers. The study further proposed the use of Python program to automate the studies through scaling the load down until the voltage limits are reached by sending commands to PSS/E using Python syntax. In addition to this, the use of Tabu Search (TS) algorithm is proposed for optimally selecting a combination of lines to accommodate the least load within the voltage limits. The load is scaled down automatically in PSS/E using Python program with the least load served as an objective function and the constraints being the voltage limits. The study found that the use of step-down transformers can successfully reduce the steady state overvoltages in a lightly loaded network. The introduction of Python program to automate the studies was successful. Lastly, intelligence of Tabu Search algorithm can successfully select the optimal combination of lines to serve the least load without voltage violations.M.Phil. (Electrical and Electronic Engineering