Reason for Poor Quality of Power

	There are various reasons why the power supplied by the power lines is far from ideal. Some of them are:
	Switching of high current drawing devices like lift motors, pumps, and air conditioners.
	Interference from the Telephone lines running parallel to the Power cables.
	Induction due to high voltage lines nearby, or due to lightening.
	Heavy machinery that throws a lot of noise on the lines.
	All the above-mentioned sources of disturbances create problematic conditions on the mains, which can be summarized into 9 kinds of power problems as under:
	Power Outage: This is of course the most basic power problem that is complete failure of power, i.e. mains voltage is absent.
	Power Sags: A condition wherein the mains voltage is lower than 10% of the rated supply voltage for more than 100 milli-seconds. This condition is generally caused by heavy electrical equipment being turned on.
	Power Surges: A condition wherein the mains voltage is higher than 10% of the rated supply voltage for more than 100 milli-seconds. This condition is generally caused by heavy electrical equipment being turned off.
	Brown-out: Mains voltage remaining at less than 20% of the rated voltage for extended periods of time. This is caused by an overload on the mains wiring.
	Spikes: Short bursts of high voltage on the line. Typically they are of duration less than 100 milli-seconds, and can reach voltages in excess of 1000 volts. Switching equipment, arcing or static discharge generally causes them.
	Switching Transients: Extremely short bursts of very high voltage on the line. Typically they are of duration less than 20 milli-seconds and can have voltage crossing 10,000 volts. They are generally caused by induction due to lightening.
	Line Noise: This is generally a high frequency noise super-imposed on the mains. This is caused when there is inadequate noise suppression on equipment using electric motors, relays and thyristors.
	Frequency Variation: A change of more than 4% in the mains frequency. Overloading of the mains, or excessive hunting in the power generating equipment causes this.
	Harmonic distortion: Harmonic distortion is a parameter whish defines the purity of sine- wave. An ideal or pure sine wave will have a distortion factor or harmonic content of 0 %, which is not possible practically. Any deviation from pure sine wave is called as distortion. The extent to which a wave deviates from pure sine wave is measured thro' a parameter called distortion factor or harmonic contents.
	All these results into poor quality of power supply which is not visible to the naked eye and can only be detected with help of sophisticated instruments. However, the effect of these is felt by the delicate components, which leads to damage of expensive equipment.