Effects of Harmonic Distortions Emanating from Domestic Loads on Low Voltage Installations Low Voltage Switchgears: Case Study
AbstractApplication of loads such as computing devices, mobile chargers, audio-visual, air conditioner and energy saving bulbs like Compact Fluorescent Lamps (CFLs) at domestic power end users has resulted in the increase of harmonic distortions in low voltage network. The main difference between domestic loads of today and that of few decades ago is penetration of electronic appliances with Switch Mode Power Supply (SMPS). These appliances are rapidly increasing due to technology advancement of semiconductor devices and digital controllers. The presence of harmonic distortions have adverse effects on low voltage network installed switchgears such as premature loss of distribution transformers, over-loading of neutral conductor and heating of reactive compensating feeder capacitors. In recent time, loss of distribution transformers prematurely has contributed to myriad outcry of power users and high cost of operational and maintenance (O&M) costs to power utilities. The business daily of May 2017 showed that the residential loads constitute up-to 75% of the total connected loads in Kenya (4.4 million) power end users are in the category of domestic consumers. In this regards, their effects on power system cannot be ignored/ assumed. This study investigated the level of current harmonic distortions of modern domestic appliances and harmonic levels at distribution transformers and the impact they have on distribution transformers. It was found out that current harmonic distortions were significantly higher than permissible levels at point of common coupling. The third current harmonic was found to be the most dominant harmonic order at secondary side of the distribution transformers. Worth mentioning is that Total Current Harmonic Distortions (THDi) was low when various loads were supplied together due to damping effects vis-à-vis harmonic generated by TV alone- CRO-type. It is recommended that mitigation of current harmonics using active power filter to be done at point of common coupling (PCC) to reduce the negative impact of harmonic distortions on low voltage installed switchgears.
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