The aging of transformer is a challenging problem faced by power grid system. When the transformer approaches the end of its service life or the test cannot pass and cannot be repaired, the risk of accidents in the continuous operation of the transformer increased. At this time, the equipment needs to be retired according to the relevant decommissioning guidelines, especially the design life of the transformer. In practice, the design life of transformers was 30~40 years. But at present, the vast majority of retired transformers do not exceed the their design life. The investment benefit of transformer was low, resulting in huge waste and loss. In order to improve the asset utilization of transformers, it is necessary to study and quantify the use cost and operation risk of the whole life cycle of transformers, which can be used to support the formulation of decommissioning strategy for old transformers. Firstly, the operation risks of old transformers and the reasons for the decommissioning of transformers were summarized and analyzed in this paper. Then the the method to determine the economic life of transformers was put forward . Taking 220kV power transformer as an example, its LCC cost curve and annual average cost curve were calculated, and its economic life was obtained. Finally, the decommissioning principles and decommissioning disposal strategies of old transformers was put forward, so as to improve the utilization rate of transformer assets.
 

Old transformer, Operational risk, Life cycle cost, Economic life, Retirement strategy.