Overview of the various power quality parameters

In modern energy supply a wide range of single and three-phase, non-linear loads are used in industrial networks right through to office blocks. These include lighting equipment such as lighting controls for headlamps or low energy bulbs, numerous frequency converters for heating, air conditioning and ventilation systems, frequency converters for automation technology or lifts, as well as the entire IT infrastructure with the typically used regulated switched mode power supplies. Today, one also commonly finds inverters for photovoltaic systems (PV) and uninterruptible power supplies (UPS). All of these non-linear electrical loads cause grid distortion effects to a greater or lesser extent, with a distortion of the original "clean" sinusoidal form. This results in the current or voltage waveform being distorted in the same way.

Fig.: Distorted current form through consumer electronics
Fig.: Distorted current form through consumer electronics

The reliable operation of modern plants and systems always demands a high degree of supply reliability and good power quality.

The load on the network infrastructure through electrical and electronic loads with grid distortion effects has increased significantly in recent years. Depending on the type of generation system and the operating equipment (mains feed with converter, generator), mains rigidity at the connection point and the relative size of the non-linear loads, varying strengths of grid distortion effects and influences arise.

The following power quality parameters must be taken into particular consideration:

  • Harmonics
  • Current and voltage unbalance
  • Rapid voltage changes - transients
  • Voltage dips and short-term overvoltage
  • Voltage interruption (SIs - short term interruptions)
  • Flicker
  • Phase shifting and reactive power