Power quality and its index


An ideal power system should supply power to users with constant frequency and sinusoidal waveform according to the specified voltage level. In the 3 phase AC power system, the voltage and current of each phase should be in a symmetrical state with equal amplitude and 120° phase difference. Because the parameters of system components are not ideal linear or symmetrical, coupled with imperfect control means, different load characteristics and randomness of its change, operation and various faults, this ideal state does not exist in practice, so the concept of power quality came into being.


Power quality can be defined as: the voltage, current or frequency deviation that leads to the failure of electrical equipment. Its contents include frequency deviation, voltage deviation, electromagnetic transient, power supply reliability, waveform distortion, 3 phase imbalance, voltage fluctuation and flicker.




With the emergence of new power loads and their increasing requirements for power quality, power quality problems have gradually attracted the attention of power companies and power customers. The main reasons are as follows:


  • In order to improve labor productivity and automation level, a large number of control equipment and electronic equipment based on computer system have been put into use. These devices are very sensitive to power quality, and even an abnormality of a fraction of a second may cause chaos in the factory. The user's tolerance of unqualified power supply is strictly limited to 1-2 frequency cycles of continuous power frequency.




  • Great changes have taken place in the power load structure of modern power system. Due to its nonlinearity, impulsive and unbalanced power consumption characteristics, the voltage waveform of the power grid is distorted, or the voltage fluctuation and flicker as well as the 3 phase imbalance are caused. It even causes system frequency fluctuations, etc., which can cause serious interference or "pollution" to the quality of power supply.

  • As a commodity, under the power market operation mechanism, different power generation companies, including independent power producers, compete on the generation side. The transmission and distribution system (i.e. the power company) is separated from the power generation, the independent operation and management provides the power transfer service for the generation companies and users, and the user side can also participate in the price control as an independent entity.



Application of power quality analyzer


Power quality analyzer can measure and analyze different aspects of power quality, and provide theoretical basis and data support for the next step of power quality governance.


01 Harmonic measuring:

Among various indicators of power quality, harmonic is the most common, because of the rapid growth of non-linear load and the continuous improvement of harmonic level of power grid. The abnormal and accident of electrical equipment caused by harmonic interference is increasing year by year. Therefore, the public grid harmonic standards play an important role in controlling the harm of harmonics and ensuring the safety, economic operation and normal production of the power grid and users.


02 Voltage fluctuation & flicker:

Voltage fluctuation in power grids is generally caused by fluctuating loads, the main fluctuating loads are:

  • Electric arc furnace for steelmaking;

  • Load of frequent starting motor, such as rolling mill or winch;

  • Loads intermittently energized, such as resistance welding machines and arc welding machines.

Harm of voltage fluctuation and flicker:

  • The electric light flickers, causing visual fatigue and even unbearable;

  • Motor, screen image distortion, swing, roll and brightness change;

  • The uneven speed of the motor affects the product quality and even damages the motor;

  • Computer monitoring and control equipment is not working properly.



03 Three phase voltage unbalance:

The 3 phase unbalance has the following application environment impact, long-term abnormal operation of the equipment will lead to equipment damage.

  • The influence of asymmetric operation on generator;

  • Induction motor operates under unbalanced voltage;

  • Asymmetric operation of transformer;

  • False start of relay protection and automatic device;

  • Non-characteristic harmonics of the converter;

  • Interference to computer system;

  • The increase of transmission line loss.




04 Voltage deviation:

Voltage is one of the important indicators of power quality. The quality of voltage has an important impact on the safety and economic operation of the power system, ensuring the safety of production and product quality of users, as well as the safety and life of electrical equipment. Reactive power compensation and reactive power balance are the basic conditions to ensure voltage quality.


For enterprises, ensuring the safe and stable operation of power system is to improve production efficiency. At present, the installation of voltage regulators, filters, surge suppressors, UPS uninterruptible power supplies and other power quality products in related industries has become standard configuration. With the increasing number of projects such as data centers, industrial Internet and artificial intelligence edge nodes in the future, the market opportunities for power quality management products will also continue to increase.


We are in such an open and competitive operating environment, which will inevitably inevitably puts forward higher and higher requirements for power quality, and promotes the development and continuous improvement of power quality standardization. Jiangsu Sfere Electric's research on the harm of power quality indicators to electrical equipment has made a lot of achievements. If you encounter problems in the process of solving relevant electrical problems caused by power quality, Sfere Electric will provide you with an effective solution suitable for the current situation of the enterprise. Click on our online customer service for consultation, or call the service hotline directly. We look forward to you to solve the problem for you!


Copyright © 2019.Company Name All Rights Reserved.