Optimization of Transformer Sparing and Replacement Strategies using Probabilistic Simulation

An optimal strategy for pro-active replacement and sparing of transformers within a transmission system will balance the costs of transformer replacement and the purchase of spares against the cost of transformers being out of service and the possibility of load-drop. To develop such a strategy, the failure, repair and replacement of equipment in a transmission system was simulated over many years to evaluate how various transformer and sparing strategies compare in terms of the numbers of transformers replaced and the predicted frequency of load drop from the system. The sequential Monte-Carlo simulation employed modeled transformer failures as a function of transformer age and condition. Cascading failures and failure bunching were also modeled in detail. It was concluded that an optimal strategy would combine the pro-active replacement of transformers based on their condition and their contribution to load drop and an increased number of spare transformers.