Notes

POWER QUALITY PROBLEMS & ISSUES
POWER QUALITY (PQ) is the ability of power system to operate loads without damaging or disturbing them and, also the ability of loads to operate without disturbing or reducing efficiency of the power system. IEEE Institute of Electrical and Electronic Engineers (IEEE) Standard IEEE1100 defines power quality as,“ The concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment.” Ideally, the best electrical supply would be a constant magnitude and frequency sinusoidal voltage waveform. The Power Quality of a system expresses to which degree a practical supply system resembles the ideal supply system. If the Power Quality of the network is good, then any loads connected to it will run satisfactory and efficiently. If the Power Quality of the network is bad, then loads connected to it will fail or will have a reduced lifetime, and the efficiency of the electrical installation will reduce. Electrically operated or connected equipment is affected by Power Quality. Determining the exact problems requires sophisticated electronic test equipment.
Listed here are a few symptoms that are indicators of Power Quality problems:
• Piece of equipment misoperates at the same time of day.
• Circuit breakers trip without being overloaded.
• Equipment fails during a thunderstorm, rainfall, lightning etc.
• Automated systems stop for no apparent reason.
• Electronic systems fail or fail to operate on a frequent basis.
• Electronic systems work in one location but not in another location, and many more such electrical power-related events.
The commonly used terms those describe the parameters of electrical power that describe or measure power quality are Voltage sags, Voltage variations, Interruptions Swells, Blackouts, Voltage imbalance, Distortion, Harmonics, Harmonic resonance, Interharmonics, Notching, Noise, Impulse, Spikes etc.
The issue of electric power quality is gaining importance because of several reasons:
• The society is becoming increasingly dependent on the electrical supply and its main concern is the reliability and quality of supply.
• Modern equipments and machinery in industrial and public sectors are more sensitive and highly susceptible to power quality variations.
• Failures due to such disturbances create high impact on production cost; even a small power outage has a great economical impact on the industrial consumers.
• A longer interruption harms practically all operations of a modern society.
• The advent of new power electronic equipment, such as variable speed drives and switched mode power supplies, has brought new disturbances into the supply system.
• In practice, power systems, especially the distribution systems, have numerous nonlinear loads, which significantly affect the quality of power supplies. Apart from nonlinear loads, some system events like capacitor switching, motor starting and faults also causes power quality problems.