Analysis Of Press Field And Leakage Magnetic Field On Large Power Transformers

With the rapid development of electric industry, the quantity of transformers has beenincreased fast. Meanwhile, the design and manufacture of transformer is more and moredifficult with the larger capacity and higher voltage. When the short circuit appears in theelectric system, transient state short circuit current would be Several times more than that ofrated current. At this moment, the electrodynamics force would be dozens times more thanthat under normal operation, which would form serious threat to insulation and mechanicalconstruction of transformer for such large mechanical force. In addition, with the increase ofproduct capacity, leakage magnetic field of transformer has increased, stray loss has alsoincreased, and even more serious thing is that partial overheating appeared by eddy currenteffect due the distribution of stray loss is uneven in some metal parts. If controlled not well,overheating metal parts would promote transformer oil or insulators aging and produce gasesso that transformer would be caused failure and the service life would be decreased. Finally, itwould cause thermal aging and breakdown of insulators. Even worse, it would cause sealinggaskets damage if there were some nearby and besides, cause incidents of leakage of oil etc.Therefore, in order to relieve the both above influences of leakage magnetic field, it mustbe analyzed to the leakage magnetic field of transformer. Major content as follow：Introduction the electromagnetic field theory, the type and the effect of leakage magneticfield, finite element method and MagNet software were introduced at the same time accountof the major work done in this paper.Select one power transformer three phase, two winding with OFTC, model ofSFP-1140000/500, Using MagNet software a transformer single-phase short circuitcalculation finite element model has been established, simulation the transformer short-circuittest state, to take the high voltage is applied before the low-voltage in circuit mode. transientelectromagnetic field were calculated and analyzed. The axial and radial magnetic leakagefield distribution of the winding, current waveform of short circuit, radial and axialelectromagnetic force distribution of each winding unit were gained. And then, according tothe method of GB of the winding for the dynamic stability and thermal stability ofshort-circuit strength check, the results were obtained some theoretical significance andengineering practical value, and it may provide some reference for large capacity, extra-highvoltage power transformer winding short circuit of the electromagnetic force calculation andverification.Use this power transformer model of SFP-1140000/500as a example to analyses thePotentially overheating in tank near the LV lead, Calculate eddy current losses in the tank nearthe LV lead, and contrast test results.