Power quality has become an important issue as more and more customers install and use electronically sensitive equipment. This section discusses power factor and harmonic distortion.
Power Factor represents the amount of current and voltage the customer actually uses compared to what the utility must supply. A high power factor is considered to be 90% and higher. A low power factor ballast will draw more current than a high power factor ballast for the same wattage lamp. The result is that fewer fixtures can operate on a given circuit.
Some utilities charge customers who have low power factors, because low power factor affects their distribution wires the same way. Low power factors are more common with compact fluorescent technology. Industrial facilities with inductive loads such as motors will very often have low power factor and may be charged extra by the utility.
Harmonic distortion is a specific type of current and voltage contamination. With harmonic distortion the pure sinusoidal waveform is deformed. One of the possible causes is lighting, and in particular, electronic ballasts.
However, today's quality electronic ballasts cause no more distortion than magnetic ballasts (which have been in use for a long time.) Ballasts have Total Harmonic Distortion (or THD) ratings of less than 30%, most falling below 20%.
Other equipment can also generate harmonics including variable frequency drives, personal computers, programmable controllers and solid state switching devices. Harmonics can also enter a facility in from outside, a neighboring facility, for example.
High harmonic distortion can have negatively impact a building's electric distribution system. It can generate excessive heat in motors causing early failures. Heat also builds up in wire insulation causing breakdown and failure. Increased operating temperatures can affect other equipment, causing malfunctions and early failure.
Power quality experts can conduct a survey of the facility to determine the cause of harmful harmonics and recommend solutions. Power filtering devices are available. Also, sometimes, lighting circuits can be isolated from other circuits in the electric distribution system.
High harmonic distortion levels are most common in hospitals, industrial facilities and offices with a high concentration of computers, although any building can be a candidate. Common symptoms of harmonic distortion include: frequently tripped circuit breakers or blown fuses, motor winding failures, computer failures and telephone interference.
