| The operation safety and reliability of transformer which is a kind of the necessaryelectrical equipment in grid construction have always drawn people’s attention. With thedevelopment of ultra-high-voltage (UHV) power grid, the inside electromagnetic forceof transformer is growing with the unceasing enhancement of voltage level and theincreasing capacity of transformer. DC bias caused by geomagnectically induced currenthas been a research hot spot constantly since March13,1989when a severegeomagnetic storm in North American affected the normal operation of power systemseriously. Scholars have carried out a lot of related researches about the transformervibration mechanism. But, few research concerns the change of transformer vibrationmechanism under the DC bias affect. Thus, in this paper, researches have been carriedout in this aspect. Theoretic mathematical formula derivation, electromagnetic-structurecoupling field modeling, several research means and methods like developing thetransformer vibration monitoring system, building experiment platform to carry out therelated experiments, separating the transformer vibration data acquired fromexperiments through blind source separation technology were adopted in this paper.The main innovation work of this paper includes the following points:①Considering the DC bias affect and combined with the existing transformervibration related theory, the electromagnetic force equations and displacement equationsof transformer coil and core have been deduced in this paper. Based on this, change ruleof coil and core following the DC bias value are discussed. Considering the influence ofmagnetostriction electromagnetic-structure, coupling field modeling is built. Based onthe model, inside magnetic flux density of transformer, mechanical stress distribution,tension distribution and displacement distribution change rule under the DC biasinfluence are investigated.②In order to further study the influence of the electric power harmonic totransformer vibration, an AC arc furnace model based on chaos circuit is set up. Themodel can well simulate the nonlinear characteristics of practical electric arc voltageand arc current in grid. Especially, it simulates the characteristics of chaos. Using thesimulated electric arc furnace model as harmonic source, winding and core vibrationchange rule under harmonic affect is investigated through simulation. The vibration dataobtained by simulating real environment is more convincing. ③The transformer vibration on-line monitoring system is developed in this paper.LabView is selected as the development platform. The functions like Channel signalreal-time display, real-time spectrum display, channel selection, choice of trigger, triggersettings, and data storage, etc. are achieved in the system. Especially, a new data storagetechnology is applied. Complex monitoring tasks is managed through creating adatabase. The on-line monitoring system can not only accomplish the measurement taskin this paper, but can also be used as a general digital storage oscilloscope. Experimentplatform is built in this paper, on which the work carried out in this paper is completed,including the relation study between the different DC bias value and transformervibration behavior, the affect of different load and three-phase imbalance to transformervibration under the same DC bias, etc.. This work fills the blank of the direction of thistopic research.④The research method of blind source separation technology based on FastICAis proposed in this paper to investigate the relationship between DC bias andtransformer vibration. According to the characteristics of isolated signal, coil and corevibration signals are identified. Winding and core vibration change rule under DC biasis investigated respectively. Compared with researches in the related subjects using thetransformer body vibration signal as research object, it well reveals the essence oftransformer vibration. |
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