Aims: The purpose of the study is to use Fast Voltage Stability Index to find out the
weakest line of the system so that the weakest transformer of the system can be find out.
Methods: In this paper, a technique is proposed to decide the priority selecting the out of service
transformer for repair/replacement. Based on voltage stability, priority is assigned for repairing or
replacing the particular transformer.
Results: By using this method, a number of out of service transformers in the transmission line can
be determined and then replaced or repaired. The technique has been implemented in MATLAB
software, which is used to rank all the out of service transformer in the system. This MATLAB program
has been developed to conduct load-flow studies including Voltage Stability Index. The FVSI
proposed by Musirin et al. has been used in this work to rank the transformers which needs repair/
replacement. Transformer located at weakest line should be repaired first technically.
Conclusion: The proposed method in this paper aims to improve the reliability and to manage the
congestion of the transmission system by repairing or replacing out of service transformer.