Poor power quality increases electricity bills and often causes equipment failure. Naturally, we want good power quality. Does this mean we need to get rid of harmonics?
Not necessarily. You can have (some) harmonic distortion and not have a problem with your power quality. You can have problems with your power quality and not have harmonics. Power quality encompasses much more than harmonic content.
To determine whether your power quality is adequate, you really need to do an intensive survey of your distribution system and of the power at your critical loads. Two common problems are:
- Power factor. This is a function of how much capacitance and inductance your load has. Motors are inductive loads, so in facilities with many motors you will have low power factor unless you have power factor correction. And that’s always going to be in the form of added capacitance. You want power factor to be close to unity, so you add capacitors to offset this. Don’t add capacitors to motor/drive sets; replace the drive with a power factor corrected one.
- Voltage sags. A sag is a low voltage condition that is longer than merely transient. To figure out what corrective measure to take, you’ll need to collect data using a power analyzer at the service and then at progressively lower levels in the distribution system.
Violations of the NEC, Article 250, Part V are nearly always present in a facility experiencing power quality problems. Look there, first.