What does power quality mean and why power quality is so important

What does power quality mean and why power quality is so important

Electrical energy is the most important and widely used as a convenient form of energy. Modern life is depended upon the continuity of electrical power, and this makes the system reliability and power quality issues an important factor in the electric power system. Power quality refers to the quality of the voltage, the quality signifies the deviation of the voltage magnitude and frequency from the rated values and the deviations of the waveform from a pure sinusoid. So power quality is so important in our modern-day to day life. A good power quality doesn’t have a variation of the voltage magnitude, outages, impulses, flicker, a variation of the frequency, and unbalances in three-phase systems. Power quality can be defined as the arbitrary point of the system.

What is a good power quality and what is power quality problems

A good power quality means it has good voltage quality, it means that the voltage magnitude and frequency won’t be varied from the rated values and also the waveform won’t deviate from the pure sinusoid. In a good power supply there won’t be any variation in voltage, there would be a steady supply of voltage and it would stay equal to the rated values. If the power quality is not good then it would badly affect the equipment which uses this power, there is a good chance for the malfunction of the device or it could be permanently damaged. Power quality problems are created by auxiliary sources, non-linear circuit components, or non-linear loads.

What are the major power quality issues and what are the causes of poor power quality

Some of the major problems regarding the power quality are power factor correction capacitor failure, tripping of circuit breaker for no visible reason, malfunction of computer or communication failure, conductor failure of heating, shutting down of electronic equipment, fuses blowing for no apparent reason, motor failures, and over-heating, neutral conductors and terminal failures, overheating of metal enclosures, transformer failures and overheating. These issues which can be caused in a production plant would result in great loss, damage to the equipment, and this would create a lot of economic loss.

Poor power quality can be caused by the variation of voltage magnitude and frequency. Variation in magnitude can be caused by the sudden rise or fall of the load, outages, power electronic converters. Frequency variation could happen by system dynamics

What is an interruption in power quality

Interruption in power quality occurs when the supply voltage or load current decreases to less than 0.1pu for a period of time not exceeding 1 minute. They are occurred due to power system faults, equipment failures, and control malfunctions.

What is power quality monitoring

Power quality monitoring can be done by using digital fault recorders these instruments can be used to check the power quality. SCADA can be used to monitor the power flow in a power system it is a software, which will detect and report faults.

What are the effects of bad power quality

  • Computers/communication systems: loss of data
  • Automated manufacturing: loss of production
  • Failure of capacitor used for power factor correction
  • Increased loss in cables, transformers, and conductors
  • Error in energy meter reading
  • Incorrect operation of protective relays
  • Malfunction and failure of power system components

What are the major power quality problems


Transients can also be called as surge, the duration of transients varies from several microseconds to few milliseconds. Transients can cause destruction of components and of insulation materials, electromagnetic interferences. Transients are classified into two types impulsive and oscillatory.


Overvoltage is an increase in RMS AC voltage which would be greater than 110 percent at the power frequency for a duration longer than 1 minute. They occur as a result of switching of large loads, energizing capacitor banks.


An under-voltage is a decrease in the RMS AC voltage to less than 90 percent at the power frequency for a duration longer than 1 minute. They mostly occur while switching on of large loads.

Voltage swag

It is the reduction in the RMS voltage in the range of 10-90 percentage for a duration greater than half a mains cycle and less than 1 minute. It is caused by the faults in the transmission or distribution network.

Voltage swell

Voltage swell is an increase in voltage between 1.1 and 1.8 pu in the RMS voltage or current at power frequency for the duration from 0.5 cycles to 1 minute. It is caused by the start-stop of heavy loads, badly dimensioned power sources, and badly regulated transformer.