Comprehensive economic benefit evaluation method of transformer update based on risk assessment theory

The economic benefit evaluation of transformer update is the key issues to promote the energy-saving reconstruction of distribution systems in China. In this paper risk assessment theory is applied to evaluate the benefit of distribution transformer update. Transformer failure modes are analyzed in view of the different failure mechanisms in various operating phases and characteristics of all kinds of failure modes are introduced. Unavailability of repairable and non-repairable forced failures is separately derived based on the probability theory. Quantified unavailability is integrated with the corresponding power outage loss caused by transformer failures to calculate transformer operational risks. And the risk difference also known as risk return between old transformer and updated transformer is calculated by discrete numerical analysis. Based on payback period method, the comprehensive economic benefit model of distribution transformer update is presented by integrating the risk return,old transformer residual value,decreasing reactive power compensation cost, decreasing transmission and generating capacity investment and annual power loss saving of networks. Simulation shows that as risk return and decreasing transmission and generating capacity investment are taken into account, the payback period of transformer update project becomes greatly shorter, furthermore SH15-type transformer´s energy-saving effect is superior to S13-type transformer. The proposed model is more integrated and rational than traditional evaluation methods in accord with Entire Life-Cycle Management Viewpoint and offers a new idea for economic benefit evaluation of transformer update project.