Influence of Transformer Axial-Clamping Loss on the Vibration of Transformers

Due to ageing and dynamic loads, the short circuit strength of transformers in secondary distribution can be reduced. An insufficient short circuit strength may result from reduced axial winding clamping. Vibration analysis offers a promising way in a non-invasive manner to identify changes in the winding clamping. In this paper, experimental investigations are carried out to analyze the influence of axial clamping losses on the transformer vibration. The vibration is measured by fourteen vibration sensors positioned at the side surface of the transformer tank. The clamping of the windings is incrementally decreased to analyze its influence. For each decrement, the transformer is powered in ohmic load scenarios ranging from no-load tests up to rated power tests. The impact of these clamping reductions on the 100 Hz vibration component is analyzed. The results show that the identification of clamping loss depends on the sensor position. Based on the chosen evaluation criteria, only two out of fourteen sensors enable an identification of clamping loss. Furthermore, it can be concluded that the identification of the winding clamping loss is load-dependent. The optimal load to identify winding clamping loss for the tested transformer ranges from 56 % rated power to 65 % rated power.