With the rapid development of China's economy and society, the problem of power quality has become one of the increasing concerns of power users. For power users, the development of power quality management, although there are some fixed investment in the early stage, but the late return is considerable.

 

To carry out power quality management on the user side can not only avoid the power users from being fined by the power grid company because of the power factor not up to the standard, but also effectively save electricity charges and ensure the safe, stable and efficient operation of the equipment. Therefore, power quality management on the user side is gradually recognized by most power users. Then, what are the main power quality problems on the user side? In which industries are power quality problems concentrated? China electric power news reporter interviewed hebei wobang electric power technology co., LTD. (referred to as "wobang") general manager ma hongliang, wobang marketing manager li zhichao.

 

Harmonic control and reactive power compensation are the main melody

 

Ma hongliang introduced that, compared with the power grid, the power quality problems on the user side mainly include many harmonics and low power factor, so harmonic control and reactive power compensation are the focus of power quality control on the user side.

 

Harmonics are generated from various nonlinear loads. With the development of power electronics technology, the number of nonlinear load devices in the equipment used by power users increases greatly, from a small energy-saving lamp, a computer, to large rail transit traction equipment, medical CT machine, and so on. These devices are all sources of harmonics.

 

The loss of harmonics generated by various nonlinear loads to power users should not be underestimated. First, it will cause the aging and overheating of electrical equipment, aging will reduce the service life of equipment, pull up the use cost of equipment, overheating is easy to cause fire. Second, it will affect the use of equipment quality, such as motor vibration and noise, affect production and life. Third, it will cause misoperation and rejection of equipment, resulting in such as measuring device error, relay protection device abnormal action and other accidents.

 

The harm of harmonic is many, but harmonic is a power quality problem which is not easy to be found, so the majority of power users need to pay special attention to it.

 

For example, li zhichao said: "for a period of time, the production equipment of a factory often produces a variety of noise, and the yield of products produced greatly reduced, the factory always did not find out the reason at the beginning, and finally through the power quality testing institutions found that the 'culprit' is too high harmonic distortion rate.

 

If the influence of harmonics on power users is hidden, the influence of power factor on power users is much more obvious. In order to improve the energy efficiency, power grid companies will impose fines on power users whose power factor does not meet the standards.

 

The power factor is the ratio of active power and apparent power. In a certain case of apparent power, the power factor can be improved by increasing active power. In order to ensure the maximum value of active power, it is necessary to install a reactive power compensation device on the load side to minimize the value of reactive power transmitted by the power grid.

 

For power users, the increase of power factor through reactive power compensation can not only avoid the penalty of power factor not up to standard, but also save some electricity charges for power users, increase the transformer margin, and drive more power equipment.

 

After decades of development, China's reactive power compensation devices have been developed from pure capacitor compensation devices to series reactor safety capacitor compensation devices and low voltage SVG compensation devices. With the development of technology, the compensation effect of reactive power compensation device is more and more obvious, and the compensation method is more and more flexible.

 

Five industries are key areas

 

In the power user market, the five major industries are the concentrated areas of power quality governance demand and the important growth poles of governance demand.

 

In recent years, with the rapid development of electronic information technology in China, the number of data centers is increasing and the scale is increasing. At the same time, the problem of power quality in data center is becoming more and more prominent.

 

Li zhichao said that the data center on the one hand requires high power quality, on the other hand is an important source of harmonic generation, take the bank's data center as an example, power quality problems may lead to the loss of bank data, resulting in economic losses. However, the power supply system of the data center, such as UPS, IT system and refrigeration system, such as variable frequency air conditioning, refrigeration equipment, etc., will generate a large number of harmonics. With the development of cloud computing and big data industry in China, there will be more and more data centers in the future, and the power quality governance needs of data centers will be more and more vigorous.

 

Rail transit is also one of the fields with many power quality problems on the user side in China. The main problems include harmonic, low power factor and three-phase imbalance.

 

At present, the subway vehicles in China are drawn by dc, and the traction power supply equipment will produce a large number of high order harmonics. The more vehicles, the shorter the interval, the greater the harmonic. In addition, due to the need of energy saving and consumption reduction, a large number of frequency conversion equipment. Such as: variable frequency fan, electronic rectification energy-saving lamp, UPS, etc. These loads produce a large number of low - order harmonics. During the operation of the subway, the work harmonics of all kinds of nonlinear loads are large, and a large amount of capacitive reactive power is returned to the grid due to the low load and long cable, resulting in a fine.

 

In the car industry, too, power quality is a problem. There are different power quality problems in each type of workshop, among which the equipment in the stamping workshop adopts frequency conversion method to adjust the oil pump, which is easy to generate harmonics. The electric load of coating workshop is mainly fan and rectifier, and the rectifier also contains a lot of high order harmonics. Welding workshop spot welder is a typical impact load, spot welder intermittent work, power factor is low, generally around 0.5.

 

In the hospital, the power quality problem produces the source many, the harm is great. The hospital's power distribution system and some medical equipment, easy to produce a large number of harmonics, these harmonics will cause the medical equipment to lose the image, data, heavy will cause the equipment to die, and even cause the internal electronic device discharge and breakdown, bring huge losses.

 

In addition, the power system, lighting system and office system in municipal buildings are also areas where power quality problems are concentrated. With the continuous improvement of office intelligence level, the requirements for power quality will be correspondingly improved.