30-05-2012, 03:56 PM
POWER QUALITY-PQ
POWER QUALITY-PQ.ppt (Size: 2.16 MB / Downloads: 79)
What is Power quality ?
Definition : “Power quality problem is any power problem manifested in voltage, current, or frequency deviation that results in failure or misoperation of customer equipment”.
Power quality can be simply defined as shown in the interaction diagram:
Why are we concerned about PQ
North American industries lose Tens-of-Billions of Dollars every year in downtime due to power quality problems. (Electrical Business Magazine)
Load nonlinearities in rising and is expected to reach 50 to 70% in the year 2005 (Electric Power Research Institute) [Computers, UPS, fax machines, printers, fluorescent lighting, ASD, industrial rectifiers, DC drives, arc welders, etc).
The characteristics of the electric loads have changed.
Harmonics are continuous problem not transient or intermittent.
Power Quality Issue and Problem Formulation
Power Quality issues can be roughly broken into a number of sub-categories:
Harmonics (sub, super and interharmonics);
Voltage swells, sags, fluctuations, flicker, and transients
Voltage magnitude and frequency deviation, voltage imbalance (3ph sys.)
Hot grounding loops and ground potential rise (GPR)–Safety & Fire Hazards
Monitoring and measurement.
Power Quality PQ Issue and Problem Formulation
Harmonics and NLL issues:
The harmonic issue (waveform distortion) is a top priority to for all equipment manufacturer, users and Electric Utilities (New IEC, ANSI, IEEE Standards).