Modeling the Effect of Total Harmonic Distortion on Power Quality of Supply Case Study- Hisham Hijjawi College of Technology)

This research analyzed the impacts of total harmonic distortion on the power quality in the College. The College fed by 6.6KV line from Northern Electrical Distribution Company 'NEDCO'. It purchases the electricity bill at the low voltage side, the rate is “0.7"NIS for each kWh consumed, the college transformer capacity 1000KVA and, the college using one diesel generator with 130 KVA as standby supply, and The power factor in the College changing from 0.83 to 0.94 . The objective of this research is to estimate the impacts of the THD on the electrical including ,cable losses, transformer losses, the effect of THD on the power factor, how we can reduce THD, environmental impact of low power quality in the College, and to find answers to the main question ‘why do we have harmonic distortion in the College?’. Total harmonic current distortion THDi changes during the day from (8%-24%).we can note that the worst case of the THDi occurs in the night due to discharging lamps, which act as a non-linear load. The electrical energy saving will be around 74 kWh/year by improving the power factor from 0.89 to 0.98 through installing variable capacitor bank with capacity QC=25KVAR. The electrical energy losses due to THDi increase the electrical energy losses in the transformer by 41KWh/year, and also increase the electrical energy losses in cable by 68KWh / year. From other side the low load factor of the transformer in the college increased the electrical losses of the transformer by 7230KWh/year, as its effects on energy efficiency. Through the analysis of THD we found that the useful capacity of the transformer in the college decreases from 1000KVA to 887KVA due to harmonic losses. The low load factor of the transformer in the college, affecting on the level of the THDi, we also found out that when the load factor of the transformer in the college changes from (10% - 100%) the THDi decrease from (15%-5%). We used MATLAB/SIMULINK to show the impacts of the THD on the power factor as well as to reduce the THD using "Passive Filter, Shunt Active Filter, and Pulse Width Modulation "PWM". By using, Pulse Width Modulation "PWM" we noted that the THDi decreases (26%-3.7%) when the carrier frequency increases from (50-2000Hz), also we found out that THDi’s decreases from (185%-4%) when the modulation index increases from (0.1-0.9) and a passive filter the THDi reduces from (30%-3.6%), and shunt active filter which reduce THDi from (21%-2.8%). The electrical energy losses due to low power quality lead to more coal combustion, which in turn leads to increase environmental impacts. We found out that the electrical energy saving is 7900KWh/year when improving low power quality in the College which in turn saves 4.3 tons of coal per year, and 7.5 tons of carbon dioxide per year.