1. The nonlinear problem of power system components.Power quality monitoring仪Mainly including: harmonics generated by the generator; Harmonics generated by transformers; Harmonics generated by direct current transmission; The amplification effect of transmission lines, especially ultra-high voltage transmission lines, on harmonics. In addition, there are factors such as parallel capacitor compensation devices in substations that affect harmonics, among which DC transmission is currently the larger harmonic source in the power system.

2. Nonlinear load: In industrial and domestic electricity loads, nonlinear load accounts for a large proportion, which is the main source of harmonic problems in the power system. Electric arc furnaces are the main nonlinear loads, and their harmonics are mainly caused by the delay of arc initiation and the severe nonlinearity of the arc. In the living load of residents, the volt ampere characteristics of fluorescent lamps are severely nonlinear and can also cause serious harmonic currents, with a high content of third harmonic. High power rectification or frequency conversion devices can also generate serious harmonic currents, causing serious pollution to the power grid and reducing power factor.

3. Internal and external faults in the operation of power systems can also cause power quality problems, such as various short circuit faults, natural disasters, human error operations, changes in the working status of generators and excitation systems during power grid faults, and startup of power electronic equipment in fault protection devices.

The issue of power quality is a collective term for many single types of interference problems in power systems, and its essence is voltage quality issues. Power quality problems can be divided into steady-state power quality problems and dynamic power quality problems based on their generation and duration.