| Summary: | 碩士 === 國立雲林科技大學 === 電機工程系碩士班 === 95 === The power transformers are mainly made for voltage transferring for power, which should withstand high voltage stress, large current, wide temperature range and electromagnetic strength for long time duration. Since a transformer failure usually causes damages and blackout with tremendous losses. Hence it is an important issue to maintain the transformer with normal operations even to prolong its lifetime and predict the failure for preventing damages occurred. This thesis discusses the transformer tests and diagnosis techniques and integrates the related tests for early finding the internal abnormal phenomenon and further determining the failure type and location that will be developed.
Power quality is becoming an increasingly important topic due to the growing numbers and power rating of nonlinear power device used in controlling power apparatuses in industrial power distribution systems.The power quality events could be resulted as motor overheatings,communication interference and malfunction of protection devices in the power systems.
This thesis in accordance with power harmonic theory to use as harmonic and power meter and measured the load center panel of each factory. Use personal computer to record the data of harmonic current and voltage. To test and verify harmonic theory with understand equipment known. To understand equipment unknown related to produce of harmonic.Each factory harmonic data of equipment had record in this paper. The thesis uses the harmonic current measured from the power system to simulate the harmonic voltage distribution of the system with different filters, in order to find the most appropriate filter design,which tends to prevent the system from the resonance.
For improving the power quality, mitigating the damage due to harmonic and to agree with the regulations of harmonic restriction, most of the power consumers with harmonic load install the harmonic filters to reduce the harmonic current to the system and improve the power factor simultaneously. In the broad terms, two categories of harmonic filter namely passive filter and active filter can be used.
It is necessary to select suitable sets of filter which take the variation on system characteristic into consideration. This thesis proposes the optimal installation plan of passive harmonic filter considering the multiple loads and harmonic levels based on muti-type and muti-set of filter.The first stage is optimal planning based on load curve information and the change the parameters of the passive filters based on load levels and harmonic levels to agree with power factor correction and harmonic filtered demand of each load levels.The second part is to add a parallel active power filter in system, whose function is to get the same scale and phase of nonlinear load through sensing equipment and then product the combination of the same scale but opposite phase by active filter to cancel the harmonic caused by nonlinear load.
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