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This dissertation presents a survey of harmonic voltage and current distortion levels at 40 substation transformers in the north of Taiwan in order to get existing harmonic data. The 95% cumulative probability is doadopted to get background levels of harmonic voltage. The regression modelare used to predict growth trends of harmonic voltage and current for trantransformers with different load types. The prediction results show that hharmonics have higher growth trends when the substation transformer upplisupplies residential and commercial customers and the harmonic distortionsin the off-peak load period are more serious than during the peak. While the linear regression analysis is suitable for harmonic voltage, the xponexponential regression analysis is good for harmonic currents. The models of feeders and loads and the methods of harmonic analysis in a distributiosystem are studied. It is important that proper load models are used for different customers in the simulation. In order to get information of armharmonic behaviors in a distribution system, the methods of harmonic flow and frequency scan are adopted in the simulations on a basic distribution network for feeders with different load types. The results of simulations show that (1) if substation capacitor units are switched off, the resonantfrequencies of the distribution network are close to the 5th and 7th armoharmonic orders. (2) the resonant frequencies will be changed if there aredifferent feeder capacitor units. (3) the points of resonant frequency areshifted significantly by high voltage capacitor units of customers so thatharmonic distortions are more serious than basic network. (4) the harmonicflows are affected by load transfer. (5) the effects of customer loads on harmonics depend on the system conditions. It is a feasible method that xexisting feeder capacitor units are changed into filters to solve harmonicproblems. The resonant points could be shifted to other orders so that arharmonics are amplified. In order to ensure filters safety, it is ecommenrecommended to install protection equipment for unbalance, surge, and overvoltage protection. At last, in the review procedures of a utility forharmonic customers, the voltage and current distortion, ampers of harmoniccurrent, and resonant point are recommended to be included within the review procedures. The better strategies to solve harmonic problems must include (a) producing lower harmonic equipment by manufacturers, (b) reducing harmonic current to the power system from customers, and (c) checking electrical diagram by the utility.
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