Enterprise background
A well-known listed company mainly produces and sells white cardboard, cultural paper, cardboard paper, gypsum protective paper, and papermaking wood pulp. The company has offices in 30 provinces, cities, and autonomous regions across the country, and its products are exported to Southeast Asia and other countries and regions.
The listed company has an annual production capacity of one million tons of machine made paper. Information media paper and writing paper are national inspection free products, and the enterprise's information construction is listed in the top 500 in China. The company attaches great importance to scientific and technological research and development. In recent years, it has continuously increased investment in research and development, introduced and trained scientific and technological talents, and established cooperative relationships with multiple research institutes. It now has multiple inventions and patents, and has undertaken the construction of the Torch Plan of the Ministry of Science and Technology. The company has obtained international quality system certification and adopted the international standard product logo certificate, and the product quality standards are in line with international standards.
Main equipment and test data of the project
01 On site situation
The production of the company cannot be separated from the paper machine, as the matching ABB frequency converter can be connected in series between the paper machine and the power supply to achieve the adjustment of the motor speed. However, due to the fact that the frequency converter is a non-linear device, it will inevitably generate high-order harmonics during operation, which will have adverse effects on the motor. The frequency of the input current of an electric motor operating under variable frequency speed regulation is a variable, and adjusting the motor speed can be achieved by changing the frequency of the input current. However, due to the variation of input current frequency, it will have an impact on the shaft power output of the motor.
However, for motors operating under variable frequency speed regulation conditions, the input current contains a considerable amount of high-order harmonics, which can cause additional losses due to harmonic currents. At the same time, due to the influence of harmonic currents, there is a decrease in output shaft power, a decrease in operating efficiency, an increase in temperature rise, and other abnormal situations. In addition, the additional magnetic field generated by harmonic currents, which rotates at a high speed relative to the shaft, generates a higher shaft potential and can break through the oil film of the bearing, causing the shaft current to flow through the bearing and cause damage. There is distributed capacitance between the coils of the electric motor. When high-order harmonic voltage is input, the voltage sharing between the coils is uneven, leading to accelerated insulation aging of the high voltage bearing coils and resulting in insulation damage to the first turn coil. In the variable frequency speed control drive system, the amplitude of the output voltage of the frequency converter is three times the rated voltage, and coupled with the high voltage change rate (du/dt) of the frequency converter, the oscillation caused by it causes the motor coil to receive greater stress, leading to insulation aging of the coil. Under high switching frequency conditions, if the length of the connecting cable between the frequency converter and the motor is too long, it will generate standing waves, which will lead to an increase in the motor terminal voltage. This high voltage will also accelerate the aging of the coil insulation and affect the service life of the motor.
Main testing equipment
Advanced power quality features and unprecedented power analysis performance
Include Fluke 435 II three-phase power quality analyzer as your insurance policy. No matter what happens to the device, with the F435 II three-phase power quality analyzer, you can rest assured. Equipped with advanced power quality measurement and energy loss cost calculation functions, this model can solve any power consumption problem.
Electrical parameter waveform data capture - capture fast RMS values to view each waveform, thereby determining how the values of voltage, current, and frequency interact with each other
Power inverter efficiency - Power inverter efficiency
Electric Energy Assessment - Quantifying the Improvement of Energy Consumption of Energy Saving Equipment Before and After Installation
First line troubleshooting - quickly diagnose screen display issues to restore online operation status
Preventive maintenance - monitoring and prediction before power quality issues cause downtime
Long term analysis - identifying difficult to detect or intermittent issues
Load Study - Verify the Capacity of Electrical Systems Before Increasing Load
Before the renovation, GE passive filtering was used to control on-site harmonics as shown in the following figure, but the harmonic control effect was not ideal enough; After the transformation, using our company's active filtering, as shown in the figure, the harmonic control effect is obvious.
Transformer Name: Main Transformer 5AA0204 Transformer Specification: 2500kVA 10/0.7kV
Transformation effect: After the power quality and harmonic control of the 6AA0202 transformer in the low-voltage distribution room, the power factor was increased to above 0.95, and the highest content of the 5th harmonic was reduced from 22.6% before the transformation to 4.8%.
Transformer Name: Main Transformer 5AA0204 Transformer Specification: 2500kVA 10/0.7kV
Transformation effect: After the power quality and harmonic control of the 6AA0608 transformer in the low-voltage distribution room, the power factor was increased to above 0.95, and the highest content of the 5th harmonic was reduced from 29.3% before the transformation to 19%.
Evaluation basis
Harmonic standards and user allowable values
01 National standard harmonic voltage limit
The harmonic voltage limits for public power grids specified in the national standard GB/T 14549-93 "Power Quality - Harmonics in Public Power Grids" are shown in the table below; The harmonic voltage distortion rate of each harmonic current in the 0.4kV busbar load injection system of a 10kV substation should be less than the harmonic voltage limit of the 0.4kV voltage level listed in the table below.
Harmonic voltage limit of public power grid (phase voltage)
02 National standard harmonic current allowable value
According to the national standard, the allowable values of each harmonic current injected into the system common contact under the approved benchmark short-circuit capacity are shown in the table below. The national standard 0.4kV standard short-circuit capacity specifies 10MVA, and the 10KV standard short-circuit capacity specifies 100MVA.
The total allowable value of harmonic current injected into the common connection point Ihp (A)
Product features and main functions
The role of active power filters
01 Enhance the operational safety and reliability of the power system
Have you ever encountered such a problem:
During the operation of transformers, there may be severe overheating without reason, even leading to serious accidents such as transformer burnout;
Unintentional action of power system protection devices, frequent burning of PLC systems, disconnection of system power, or failure of protection devices to act when they should, resulting in loss of protection of the power system and causing huge losses;
Frequent system grounding faults caused by insulation aging occur in cable lines that are still in use;
Common electrical equipment such as air conditioners often experience switch burnout faults;
Computers, televisions, and other display devices used display distortion and screen shaking;
Lighting equipment often flickers without reason
Wait
Most of the above problems are caused by harmonics in the power grid.
A more serious problem is that after an accident, due to the lack of measurement methods by users, many hidden dangers caused by design defects often make it difficult to confirm the responsibility for the accident.
The use of active power filters can effectively solve the above problems for you.
The role of 02 in energy conservation and efficiency enhancement
The harmonics present in the power system can reduce the operational efficiency of various power equipment, and the use of active filtering equipment can save some energy losses.
Harmonics will generate a portion of harmonic reactive power demand, as ordinary reactive power compensation equipment cannot compensate for harmonics. So in practice, the reactive power demand generated by harmonics has not been addressed, which has a certain impact on the operation of various power equipment. The use of active filtering equipment can be improved in this regard, playing a certain auxiliary role in the compensation of ordinary reactive power compensation equipment. By using active filtering equipment, energy savings can reach 5%.
The role of 03 in reducing consumption and emissions
The harmonics present in the power system can cause significant heat loss to users. For example:
Harmonics in the power grid can increase line losses by two times:
It will cause severe local overheating of the transformer, increasing copper and iron losses by 2.5 times;
Harmonics cause overheating and insulation aging of equipment such as transformers, capacitors, and cables, reducing their service life;
Harmonics cause a significant increase in the failure rate of most power equipment, increasing the maintenance cost for users.
Using active power filtering equipment can help you recover losses in this area.
Project summary
Through monitoring, it was found that the listed company has a high content of 5th and 7th harmonic frequencies on site; By putting into use the 690V active filtering device of Jiangsu Sifel Electric, the harmonic current generated by the load is automatically tracked and compensated, which significantly reduces the N-line current and effectively suppresses each harmonic current, improves the stability of the power supply system, eliminates the harm of harmonics on the communication system, and achieves good operating results, ensuring the safe and reliable operation of the entire system.
Through its application in the listed company, the 690V active filtering device has been put into use, ensuring that the harmonic current of the listed company decreases significantly and improving the power factor of the incoming cabinets of each transformer to 0.98. With sufficient capacity, the on-site current distortion rate has decreased from 26% to about 5%, receiving unanimous praise from users.
