Study On Application Of Vibration Analysis To The Condition Monitoring Of Power Transformers Windings

In the fault diagnosis field, electric scientists and engineers have founded some methods to monitor the conditions of internal structure such as short-circuit reactance online test, transfer function online test and etc. Practice shows that these electric means are not convenient, precise and sensitive to fault detection and identification. So considering from mechanical structure, vibration caused by windings may be used to extract eigen-parameters which contain the information about winding's fault.Theoretically the winding's vibration leads to the transformer tank and cooling-oil vibration, the conditions of the winding may be diagnosed by analyzing the vibration signal measured on transformer tank. In this thesis, taking winding and the whole transformer as research object, which are studied by theoretical analysis combined with test method. The thesis involved the following aspects: the relation between the winding vibration and axial clamping pressure, the relation between the transformer body and axial conditions, the relation between the complete transformer's vibration and clamping pressure when short-circuit, the vibration character of on-load transformer and how to monitor it online. The main work and conclusions are correspondingly listed below:The equivalent mathematical model of finite element modellings for the winding and core are proposed, the relationship between winding's vibration and its clamping pressure is discussed. Finite element modelings of the windings and core were build and there inputting parameters where identified by frequency response function gained from vibration test.Besides windings and core, the vibration tests were also done to get the frequency response function of transformer body.The primary part of this paper is to study how to monitor the clamping state of windings by the measuring the vibration of tank. In this paper, finite element modeling are used to calculate the acceleration of tank when the windings are clamped with different pressure. Rated-current tests are done to verify the calculated results. The clamping pressures are estimated along with a group of short-circuit tests. The vibration is caused by electric force whose frequency is 100Hz and the vibration signal's frequency is corresponding 100Hz with integral multiple harmonics (200Hz, 300Hz) measured by 7 acceleration and 7 pressure transducers.This paper also indicates a new method, Sensitivity Analysis of Vibration on Load to monitor the transformer when it is working. The load and no-load tests imply that this method is highly feasible.