This paper describes the design and application of low voltage reactive power compensation device. Concealed Shower Set,Shower Set,Dual Shower Head System,Rainfall Shower Combo kaiping aida sanitary ware technology co.,ltd , https://www.aidafaucet.com
Ankerui Electric Co., Ltd.
Abstract: With the rapid development of China's economy, enterprises have put forward higher requirements for the demand for power supply and the quality of power equipment. The economics of power system operation is closely related to power quality and reactive power. The design of the power compensation device was elaborated and studied, and the application of the reactive power compensation device in the field was introduced.
Keywords: power quality reactive power reactive compensation design application
0 Preface
In recent years, with the rapid development of the economy, the concept of power quality management has received extensive attention in major enterprises. The concept of “safety of electricity, quality of electricity, economy of electricity†is deeply rooted in people's minds, and reactive power compensation is used as power quality management. The important component has also become the direction of the majority of electric power research. The state has adopted an iron fist policy for enterprises that do not meet the standard of reactive power. The power rate has also become a burden for some power companies. In this paper, the design and selection of low-voltage reactive power compensation device are expounded and analyzed, and the operation and application of low-voltage reactive power device in the field are illustrated.
1 active power and reactive power
In an AC circuit, there are two types of electric power supplied by a power source; one is active power and the other is reactive power. .png)
Active power is the electrical power required to keep a consumer operating normally, that is, the electrical power that converts electrical energy into other forms of energy (mechanical, optical, thermal).
Reactive power is relatively abstract, it is used to exchange electric and magnetic fields in the circuit, and is used to establish and maintain the electrical power of the magnetic field in electrical equipment.
The relationship between apparent power, active power, and reactive power can be derived from the power triangle. The formula is as follows: .png)
.png)
For example, the motor needs to establish and maintain a rotating magnetic field to rotate the rotor, thereby driving the mechanical motion. The rotor magnetic field of the motor is established by taking reactive power from the power source. The transformer also needs reactive power to generate a magnetic field in the primary coil of the transformer and induce a voltage in the secondary coil.
Therefore, reactive power is not useless power, and it occupies an important position in the power system. Without reactive power, the motor will not rotate, the transformer will not be transformed, and the AC contactor will not pull.
2 Introduction to low voltage reactive power compensation device .png)
The low-voltage reactive power compensation device plays a role in improving the power factor of the power grid, reducing the loss of the power supply transformer and the transmission line, improving the power supply efficiency, and improving the power supply environment. Therefore, the reactive power compensation device is in an indispensable position in the power supply system. Reasonable selection of low-voltage reactive power compensation device can minimize the loss of the network and improve the quality of the user's electricity. Conversely, unreasonable selection or improper use of methods may also cause various uncontrollable factors such as voltage fluctuations, flicker, and harmonic amplification of the power supply system.
3 Principle of reactive power compensation device
As can be seen from the power triangle, the user's transformer capacity (S) is fixed. If the reactive power (Q) required by the user's equipment is too large, the output of the active power (P) will be reduced. This will not only make the electrical equipment not work properly, but also cause the equipment to be damaged due to overload of the line. At this time, it is necessary to compensate the power system for reactive power.
As shown in Fig. 1, before the reactive power compensation, the reactive power and active power of the load are all from the power grid through the transformer, which leads to a decrease in the power factor of the power grid, a decrease in power quality, and a poor power utilization efficiency.
Figure 2 compensates the device for reactive power. At this time, the active power of the device comes from the power grid through the transformer, and the reactive power is taken from our reactive power compensation device. Assume that the reactive power of the device is extracted from the reactive power compensation device. At this time, from the grid side, the reactive power (Q) is 0, and the apparent power (S) at this time is equal to the active power (P), and the power factor. Is 1. At this time, the power supply efficiency of the power grid is the highest. Although this situation is an ideal state, in the actual operation process, as long as the compensation is proper, the monthly average power factor is above 0.95. .png)
.png)
Fig.1 Pre-reactive compensation legend Fig.2 Reactive compensation diagram
4 The importance of reactive power compensation
In general, the use of reactive power compensation devices to improve the power factor is reflected in two aspects: First, it can reduce the power loss on the transmission line; Second, the potential of power equipment (such as motors, transformers, etc.) can be fully utilized. Because the electric appliance always works under a certain voltage and a certain active power, if the power factor is low, a large current is used to ensure the normal operation of the electric appliance, and the transmission current becomes large, resulting in an increase in line loss. In addition, any power equipment always works within a certain rated voltage and rated current. If the rated voltage exceeds the rated voltage, it will threaten the insulation performance of the equipment. If the working current exceeds the rated value, the internal temperature rise will be too high, thus reducing the equipment. The service life. For some power generation equipment, the increase of power factor can greatly increase the efficiency. For example, if a generator has a capacity of 1500 kW, when the power factor of the power system is increased from 0.6 to 0.8, the actual power generation capacity can be increased to 3000 kW.
5 Economic benefits of reactive power compensation
The economic benefits of reactive power compensation are mainly reflected in the power rate electricity rate, the power rate electricity rate = active power × electricity price × force rate electricity tariff adjustment factor. The power rate adjustment factor is obtained based on the value of the power factor. See Table 1 and Table 2 for the power rate adjustment factors for different benchmarks.
Table 1 Valuation rate electricity meter adjustment table with 0.90 as standard .png)
Table 2: 0.85 is the standard worth of electricity rate adjustment table .png)
The state also stipulates the standard value. Any user who needs transformer power of 100kVA and above 10kV power supply should conduct power factor assessment. The specific standards are as follows:
♦ For users below 100kVA and 160kVA (excluding 160kVA), the power factor needs to reach 0.85;
♦ User power factor above 160kVA should be above 0.90.
♦ The user's power factor is greater than the standard to reduce their monthly electricity bill, which is lower than the standard increase of their monthly electricity bill.
For example: a transformer user's transformer capacity is 160kVA, using low-voltage metering, a month to change the user's consumption of active power is 25000kWH, reactive power is 27000kWH, assuming electricity costs of 0.68 yuan / kWh. According to the survey data, the active loss of the transformer is 1036 kWH, and the reactive power loss is 3790 kWH. Therefore, the user consumes a total of 26,036 kWH of active power and consumes 30,790 kWH of reactive power. The power factor is 0.65 by the power triangle or table lookup. . Through the look-up table, the user's power rate adjustment factor is +15%, and the total electricity consumption fee is 25000×0.68 for 17,000 yuan. The power rate for the additional rate is 25000×0.68×0.15 for 2550 yuan, totaling 19550 yuan. .
Now the reactive power compensation is used to increase the power factor from 0.65 to 0.95. According to the table, the user's power rate adjustment factor is -0.75%. The total electricity consumption is 25000×0.68, which is 17,000 yuan. The power rate of electricity is 25,000 × 0.68 × (-0.0075) is -127.5 yuan, a total of 16872.5 yuan.
From the example, we can see that the reactive power compensation can generate great economic benefits for the enterprise. Generally, the equipment cost can be recovered from 10 months to one year to generate income for the enterprise.
6 Selection of reactive power compensation
6.1 Capacity selection
6.1 Capacity selection
6.1.1 New Project
New projects cannot be determined due to on-site parameters. In order to facilitate rapid selection, the industry is first classified, and the categories of each industry are as follows ( .png)
, .png)
Refers to the reactive compensation capacity, .png)
Means the capacity of the transformer, .png)
Refers to the industry coefficient of reactive power compensation):
Industry, occasion
category
Industry, occasion
category
Industry, occasion
category
LED screen
II
Coal mine
III
Hospital office
I
Office building
I
Car charging station
III
Bank securities
I
Glass factory
III
Car manufacturer
III
print
III
Large supermarket
II
Commercial plaza
II
cinema
II
Electroplating factory
III
Petrochemical
III
Entertainment venue
II
Television studio
II
food processing
III
papermaking
III
Electronic processing
III
Plastic processing
III
Exhibition Center
II
power plant
III
Tunnel lighting
II
Residential building
I
Textile
III
stadium
II
Hotel
I
Wind power plant
III
library
II
Radar base station
III
Steel
III
Sewage treatment
III
metallurgy
III
port
III
Stage square
II
Medical building
II
Rail
III
Office building
I
tobacco
III
welding
III
SCHOOL
I
Machining
III
Traffic lighting
II
Pharmaceutical industry
III
I: coefficient .png)
Approx. 0.3, suitable for applications such as office buildings, residential buildings, etc., where the reactive power demand is relatively small;
II: coefficient .png)
Approx. 0.4, suitable for applications such as commercial, rail transit and other harmonics with relatively low reactive demand;
III: coefficient .png)
Approx. 0.55, suitable for heavy industrial, manufacturing and other harmonics, where the reactive power demand is relatively large;
6.1.2 Reconstruction project
Reconstruction projects generally need to go to the site for on-site measurement. According to the actual situation of the site, configure the corresponding reactive power compensation scheme. The main points to be measured include: active power, reactive power, apparent power, actual power factor, target power factor, Load status, grid background, etc. The capacity of the reactive power compensation device can be calculated by actual measurement. In the above example, it is assumed that the user transformer is fully loaded before compensation. The user transformer capacity is 160kVA, the power factor is 0.65, and the target power factor is 0.95. as follows:
Compensation front view power is .png)
Power factor .png)
, the active power before compensation is .png)
, the reactive power before compensation is .png)
.
The active power before compensation and after compensation is unchanged .png)
Target power factor .png)
, the compensation after the power is .png)
After the compensation, the reactive power is .png)
.
Therefore, the reactive power that needs to be compensated is .png)
.
6.2 Model Description 
6.3 technical parameters
Electrical parameter
Rated voltage
AC400V
Compensation capacity
60～630kvar
working frequency
50Hz
Response time
≤20ms
Overload capability
Voltage overload 1.1 times, current overload 1.3 times
Target power factor
0.8 to 1.0 (can be set)
Control characteristics
Compensation method
Total complement, sub-complement, and hybrid supplement
Number of control channels
2 to 16 circuits
control method
With manual and automatic switching mode
Switching algorithm
Cycling
Protective function
Overvoltage, undervoltage, phase loss, short circuit protection
Structure
Protection level
IP30
colour
RAL7035 (can be customized according to customer requirements)
Installation method
Indoor installation, fixed way and incoming mode
Environmental conditions
Ambient temperature
-25°C to +50°C
Relative humidity
≤50% at 40°C and ≤90% at 20°C
altitude
Below 2000 meters above sea level
7 reactive power compensation modular scheme .png)
Nowadays, the low-voltage reactive power compensation devices on the market basically adopt the whole cabinet method, which basically belongs to the “one-hammer saleâ€. Although it can meet the compensation requirements of the user site, it is very much in terms of maintenance and capacity expansion after compensation. The inconvenience is that it is very difficult to replace the entire cabinet when the user needs to carry out the transformation. Figure 3 is a reactive power compensation module, which integrates a reactive power compensation loop, including: capacitor, reactance, thyristor switching switch, fuse, and secondary circuit in a module. In actual use, modules and modules They are independent of each other and do not interfere with each other. In maintenance and use, capacity can be increased, decreased, and maintained according to modules. Figure 3 reactive power compensation module
8 ANSVC application case in Jiangsu Hongliu Sheets Co., Ltd.
8.1 Project Introduction
Project Address: Jiangsu Hongliu Sheets Co., Ltd. The project address is located in Jiangyin City, Wuxi City, Jiangsu Province. It is located in the Yangtze River in the north, Taihu Lake in the south, Changshu and Zhangjiagang in the east, and Changzhou in the west. It is located in the “Golden Triangle†geometric center of Suzhou, Wuxi and Changzhou. . The average altitude is about 6 meters, and the temperature conditions are good throughout the year, with four distinct seasons. Jiangsu Hongliu Sheets Co., Ltd. covers an area of ​​150,000 square meters and a building area of ​​120,000 square meters. The project has purchased 2 sets of reactive power compensation cabinets and 1 active filter cabinet. For reactive power compensation, the output side of 1# transformer is measured. The measurement result is shown in Figure 4. The target power factor is 0.98. The harmonic source of the field power distribution system is mainly the inverter and switching power supply. The harmonic frequency is 3 times, 5 times, 7 The second and eleventh times are typical 6n±1 characteristic harmonics, which are controlled by the ANAPF active filter to protect the capacitor. The measurement is shown in Figure 5: (black circle is the measurement point). .png)
Figure 4 Reactive power compensation field measurement results .png)
Figure 5 Schematic diagram of on-site measurement
8.2 Calculation of reactive power compensation capacity
Compensation front view power is .png)
Power factor .png)
, the active power before compensation is .png)
, the reactive power before compensation is .png)
.
The active power before compensation and after compensation is unchanged .png)
Target power factor .png)
, the compensation after the power is .png)
After the compensation, the reactive power is .png)
.
Therefore, the reactive power that needs to be compensated is .png)
.
Considering the difference between the actual compensation capacity and the nominal compensation capacity, considering that the cabinet can only be placed at a depth of 800mm, a 350kvar main cabinet and a 350kvar auxiliary cabinet are selected for a total of 700kvar.
8.3 On-site use .png)
Figure 5 Field installation diagram .png)
Figure 6 on-site completion map
9 Conclusion
This paper expounds the design and selection of low-voltage reactive power compensation device from the basic knowledge, selection parameters, economic benefits and example design of low-voltage reactive power compensation device. A new idea of ​​modular low-voltage reactive power compensation device is proposed. Reasonably configuring the low-voltage reactive power compensation device can not only reduce the line loss, improve the equipment life and operation efficiency, but also reduce the power rate fine for the enterprise, obtain the electricity fee reward, and intuitively create economic benefits.
ã€references】
GB15576-2008-T Low Voltage Complete Set of Reactive Power Compensation Device Ankerui Electric Co., Ltd. Product Manual.2013.01.
About the Author:
Yang Junjun, female, undergraduate. Position: Now working at Ankelui Electric Co., Ltd. Tel, mobile, QQ
Http://news.chinawj.com.cn Editor: (Hardware Business Network Information Center) http://news.chinawj.com.cn