Power Quality

 Is there an international quality standard ISO 100001 for Quality of Power? Not yet. But quality of the important parameters of Power, namely, continuity of service, frequency, voltage, sinusoidal waveshape are to be within acceptable limits.

Tree limbs create a short circuit in electrical lines during a storm. This will result in a power outage around these lines

Continuity of Power:

1. momentory interruption (caused by transient faults)
2. temporary interruption (a bird getting burnt)
3. outage (sustained faults in Line/Station)
4. blackout (outage in a wider area, might take days to weeks to recover)

Voltage variations:

1. voltage dip/sag (momentary): rms voltage is below the nominal voltage - but within 10% drop
2. voltage swell: rms voltage is above the nominal voltage - but within 10% limit
3. flickering : rms voltage goes above & below the nominal repetitively in lights - but within 10% variation
4. undervoltage : rms voltage drop is below 10% of nominal voltage
5. brownout: term similar to undervoltage

Other notable power quality issues:

1. Under-frquency/ over-frequency
2. Harmonics - Total harmonic distortion (waveshape distortion caused by non-linear loads such as SMPS and CFLs)
3. Transients (by switching, lightning or network faults)

Harmonics: From a pure sine wave to square wave (click for animation)