What are the main power quality problems? Such as voltage instability, the emergence of suspension or interruption, the frequency and current deviation, three-phase imbalance, or poor continuity of supply, these issues are power quality problems. In the current power system, the more serious and common problem is voltage pause or interruption and voltage waveform distortion.
The voltage is too large, and the duration of more than 1 minute, this is a typical over-voltage phenomenon, the value of 1.1-1.2 times the nominal value. This situation is mainly due to the capacitor group has been reactive compensation or load removal. If the transformer tap is not set properly will lead to over-voltage appears.
Insufficient voltage and duration of more than 1 minute, this is the under voltage phenomenon, the amplitude of 0.8-0.9 times the nominal voltage. This condition may occur during the cut-off of reactive power compensation capacitor banks and load inputs. An overvoltage can also occur if the voltage tap settings are not correct.
Voltage imbalance phenomenon is the three-phase voltage amplitude asymmetry, voltage imbalance can be said that three-phase unbalance unbalance will exceed 2%, a short period of time will be more than 4%. Various imbalances in the power system can cause three-phase voltage imbalance.
The voltage drops abruptly, in which case the voltage rms plunges in a short period of time and the value is 0.1-0.9 times nominal, which may last 0.5 cycles or one minute. This situation is likely to occur because the power system has failed.
Sudden increase in voltage, the voltage surge in a short period of time, the sudden rise of 1.1-1.8 times the nominal value, duration and voltage sag is the same, this situation is also due to power system failure caused.