Xu Shuang
Ankerui Electric Co., Ltd., Shanghai Jiading 201801
I. Introduction
Reactive power compensation is the use of reactive power compensation equipment to provide the necessary reactive power to increase the power factor of the system, reduce energy consumption and improve the voltage quality of the power grid. From the basic situation of reactive power consumption in power grids, it can be seen that all levels of networks and transmission and distribution equipment must consume a certain amount of reactive power, especially the low-voltage distribution network. The use of reactive power compensation technology to increase the power factor of low-voltage power grids and electrical equipment has become an important measure for energy-saving work (1).
Two: The main factors affecting power factor
Asynchronous motors and power transformers are the main devices that consume reactive power. The reactive power consumed by the asynchronous motor is composed of two parts: reactive power at no-load and reactive power at certain load. The main component of reactive power consumption of the transformer is that its no-load reactive power supply voltage outside the specified range will also affect the power factor. Therefore, it is necessary to seek some practical methods that can improve the power factor of the low-voltage power network so that the low-voltage network can achieve reactive local balance and achieve the effect of reducing energy consumption (2).
Third, low voltage distribution network reactive power compensation method
The main method to improve power factor is to use low-voltage reactive power compensation technology. There are three main methods that we usually use: random compensation, follower compensation, and tracking compensation (1).
(1) Random compensation: Connect the low-voltage capacitor bank and the motor in parallel, and control, protect the device and the motor. The random compensation at the same time is suitable for compensating the reactive power consumption of the motor, mainly compensating the excitation and reactive power. And the configuration is convenient and flexible, without frequent adjustment of the compensation capacity. Less investment and easy installation.
(2) With device compensation: The low-voltage capacitor is connected to the secondary side of the distribution transformer through low-voltage protection to compensate for the no-load reactive power compensation method of the distribution transformer. It can effectively compensate for no-load reactive power distribution. It is one of the most effective means to compensate for reactive power by restricting the base load of reactive power in rural networks and making this part reactive and on-site balanced, thereby increasing the utilization ratio of distribution transformers and reducing the reactive power loss.
(3) Tracking compensation: refers to the compensation method of compensating the low-voltage capacitor bank on the 0.4KV bus of the large user with the reactive power compensation switching device as the control protection device. It is applicable to special distribution transformers above 100K VA. It can replace random and follow-up two compensation methods, and the compensation effect is good.
Fourth, the choice of ARC power factor controller
Ankerui's ARC power factor controller strictly complies with the requirements specified in professional standards such as DL/T597 "Low-Voltage Reactive Power Compensation Controller Ordering Specifications" and JB/T9663 "Low-Voltage Reactive Power Automatic Compensation Controller" and other professional standards. According to the low-voltage distribution network to track the need for compensation and load characteristics. In general, the controller can be selected from the following aspects:
Table 1 Product Application
model
Load requirements
Compensation method
Switch
Capacitor
Compensation plan
ARC-6/J
ARC-8/J
ARC-10/J
ARC-12/J
ARC-6/R
ARC-8/R
ARC-10/R
ARC-12/R
Three-phase balanced load; and the reactive power is relatively stable, and users who do not need frequent switching of capacitance compensation are required.
Single-load (high-power motor) on-site compensation and low-voltage switchgear centralized compensation
Contactor
Self-healing power capacitor
Three-phase total compensation
ARC-12F-J
ARC-16F-J
Three-phase balanced load; and the reactive power is relatively stable, and users who do not need frequent switching of capacitance compensation are required.
Single-load (high-power motor) on-site compensation and low-voltage switchgear centralized compensation
Contactor
Self-healing capacitor
Three-phase total compensation, sub-supplement
ARC-12F-J
ARC-16F-J
Three-phase balanced load, or three-phase unbalanced load, variable load, impact load.
Single-load (high-power motor) on-site compensation and low-voltage switchgear centralized compensation
Capacitive non-contact switching switch
Self-healing power capacitor
Three-phase total compensation, sub-supplement
Table 2 Product Selection
Product number
Function selection table
Static output
Dynamic output
Overvoltage
Undervoltage
Overcurrent
Under current
Temperature protection
Phase protection
Harmonic protection
communication
Encoding
ARC-6/J
√
√
√
√
√
√
ARC-6/R
√
ARC-8/J
√
√
√
√
√
√
ARC-8/R
√
ARC-10/J
√
√
√
√
√
√
ARC-10R
√
ARC-12/J
√
√
√
√
√
√
ARC-12/R
√
ARC-12F-J
√
√
√
√
√
can
selected
√
√
Optional
√
ARC-12F-R
√
ARC-16F-J
√
√
√
√
√
can
selected
√
√
Optional
√
ARC-16F-R
√
Fifth, reactive power compensation capacity selection method
When the reactive power compensation capacity is mainly for the purpose of increasing the power factor, the choice of compensation capacity is divided into two major categories, namely, the selection of single-load local compensation capacity (mainly motor) and the selection of multi-load compensation capacity (referring to centralized and local grouping). make up) .
5.1 Selection of Local Load Compensation Capacity for Single Load
(1) US data recommendation: Q c = ( 1/3) P e (1/3 of rated capacity)
(2) Empirical coefficient method: Since the number of motor poles is different, the capacitor with a capacity closer to the actual need is determined by determining the empirical coefficient of the number of poles. When this method is generally used at 70% load, the post-compensation power factor may be 0.95 to 0.97. between.
Table 3 Empirical coefficient method
5.2 Selection of Multiple Load Compensation Capacity
The selection of multi-load compensation capacity is determined based on the power factor before and after compensation. Reactive power compensation capacity Qc is as follows:
VI. Benefits of reactive power compensation
Ankerui's controllers installed reactive power compensation devices on the side of the low-voltage line distribution cabinet of Jiangyin Metallurgical Co., Ltd. From the results of post-installation tests, the average current is reduced by 40 (A). The motor power factor is from The increase of 0.5 to 0.95 has reduced the consumption of the company's internal low-voltage power grid. The monthly electricity bill has been reduced from 12,000 yuan/month to 8,000 yuan/month, achieving the purpose of saving electricity. Due to the reduced input of reactive power in the grid, the metallurgical company benefits.
references:
[1] Ankerui Electric Co., Ltd. Product Selection Guide 2013.1.
[2] Selection and Significance of Reactive Power Compensation Applied to Low-voltage Netting Towels Dongtian City, Shandong Province, Administration Square, Ai Tianpeng
About the Author:
Xu Shuang, female, undergraduate, Ankerui Electric Co., Ltd., the main research direction is reactive power compensation and active filter device design; Email: Mobile QQ
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