The main indicators to measure power quality are frequency, voltage and waveform.
Frequency: rated frequency is 50 Hz. The change of frequency corresponds to the change of active load in the system, and the adjustment of frequency is one of the main responsibilities of dispatching.
Voltage: The rated voltage standards specified in national standards include: 220V for low-voltage single-phase and 380V for three-phase; The high voltage is 10, 35, 110, 220, 330, 500 and 750 kV. The change of voltage corresponds to the change of reactive load in the system, and the monitoring and adjustment of voltage are jointly carried out by the dispatching and substation. The common method is to adjust the tap of transformer and switch capacitor bank.
Waveform: The voltage waveform shall be sine wave. The harmonic current injected into the power grid by various nonlinear electrical equipment shall be limited.
Strictly speaking, the main indicators of power quality include voltage, frequency and waveform. Generally speaking, it refers to high-quality power supply, including voltage quality, current quality, power supply quality and power consumption quality.
The power quality problem can be defined as the deviation of voltage, current or frequency that leads to the failure or failure of the electrical equipment, including frequency deviation, voltage deviation, voltage fluctuation and flicker, three-phase unbalance, instantaneous or transient overvoltage, waveform distortion (harmonic), voltage sag, interruption, rise and power supply continuity.
