Cumulative Effect Properties of Transformer Insulating Paper under Multiple Short-Circuit Impacts

The insulating paper for transformer windings is an essential component in power transformers, serving the purpose of electrical insulation and mechanical support. The stability of mechanical properties of insulating paper determines the reliable operation of the transformer. The cumulative effect properties of insulating paper under multiple short-circuit impacts remain unclear. In this paper, a dynamic short-circuit force platform was built, which can generate impact forces with a transient component at 50Hz to simulate real short-circuit forces. Cumulative plastic deformation of insulating paper under different conditions such as the magnitude of short-circuit force, degree of aging, type of short-circuit, and number of short-circuit occurrences were obtained. The results indicate that the cumulative deformation of insulating paper is positively correlated with the magnitude of short-circuit force, with a maximum difference of 114.05%. The cumulative deformation of insulating paper exhibits a growth-saturation characteristic with increasing short-circuit occurrences, showing a saturation hysteresis effect, and the mathematical model conforms to the power function relationship. The cumulative deformation is positively correlated with the degree of aging, with a maximum increase of 202.78%. For aged insulating paper, the cumulative deformations caused by long-interval short-circuits are greater than those caused by short-interval short-circuits, with a maximum difference of 15.40%. The algorithm model of the equivalent relationship between short-circuit impacts with different magnitudes was proposed. The elastic modulus of insulating paper increases with raising amplitude of short-circuit forces and decreases with deepening of aging. This study demonstrates the cumulative effect properties of transformer insulating paper under multiple short-circuit impacts, which supports calculation of transformer short-circuit dynamic response and differentiation assessment of transformer short-circuit withstand capability under various conditions.