Low-pressure compensation device of submerged arc furnace

Abstract

The utility model discloses a submerged arc furnace low-voltage compensation device which comprises a power grid, a furnace transformer, a harmonic monitoring energy management and control device, a submerged arc furnace, a submerged arc furnace low-voltage filtering compensation power-saving device and a short net system compensation filter arranged in the submerged arc furnace low-voltage filtering compensation power-saving device. The furnace transformer is connected with the submerged arc furnace low-voltage filtering compensation power-saving device through the harmonic monitoring energy management and control device, the submerged arc furnace low-voltage filtering compensation power-saving device is connected with the short net through a water-cooling copper pipe, and the short net system compensation filter comprises a first transformer. According to the low-voltage compensation device for the submerged arc furnace, the submerged arc furnace short net low-voltage reactive compensation device sleeve is additionally arranged, the primary current of the submerged arc furnace short net is reduced, and meanwhile, the active power is greatly improved, so that the operating parameters and the consumption index of the submerged arc furnace are greatly improved, the smelting efficiency of the submerged arc furnace is improved, and the electric energy consumption is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of low-pressure compensation for an ore-fired furnace. Background Art

[0002] Over the years, workers at home and abroad who are engaged in the research, design, manufacturing and production of electric furnaces and their equipment have never stopped exploring and improving a series of compensation methods for electric furnaces. In my country, the introduction or self-design, manufacturing and technical equipment such as specially manufactured medium-voltage compensation with a third winding circuit transformer, secondary compensation with an anti-boost transformer connected to the secondary lead-out end of the circuit transformer, and specially manufactured longitudinal reactive power compensation with a series transformer have been put into operation in the field of electric furnaces and have achieved corresponding results. These compensation methods have their own advantages in terms of technical compensation effect and investment.

[0003] The short-circuit of the submerged arc furnace is the main power supply equipment for the secondary circuit between the transformer and the electrode of the electric furnace. It is characterized by large current, complex combined busbar, harsh working environment, large primary current of the short-circuit and large power consumption of the submerged arc furnace. The submerged arc furnace is a typical time-varying nonlinear resistor. The submerged arc furnace not only has the problem of low power factor and power quality, but also has very serious harmonic pollution. The current-voltage characteristics of the arc have obvious nonlinearity. Under the action of the sine fundamental voltage, the submerged arc furnace generates non-sinusoidal current, and the current harmonic content mainly includes 2nd, 3rd, 4th, 5th, 7th, 11th, etc., among which 2nd, 3rd, 5th, and 7th are the main ones. Under the power supply voltage level, the 2nd, 3rd, 5th, and 7th harmonic contents are 11%-14%, 6%-20%, 8%-10%, and 4%-7% respectively. These harmonic currents are injected into the power supply system of the electric furnace in large quantities, causing the voltage of the public power grid to be distorted, resulting in harmonic pollution. Utility Model Content

[0004] The utility model aims to provide a low-pressure compensation device for an electric arc furnace to solve the problems raised in the above-mentioned background technology.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A low-voltage compensation device for an ore-heating furnace comprises a power grid, a furnace transformer, a harmonic monitoring energy management device, an ore-heating furnace, a low-voltage filtering compensation and power-saving device for the ore-heating furnace, and a short-net system compensation filter arranged in the low-voltage filtering compensation and power-saving device for the ore-heating furnace, wherein the power grid is connected to the furnace transformer, the furnace transformer is connected to the ore-heating furnace through the short-net, the furnace transformer is connected to the low-voltage filtering compensation and power-saving device for the ore-heating furnace through the harmonic monitoring energy management device, the low-voltage filtering compensation and power-saving device for the ore-heating furnace is connected to the short-net through a water-cooled copper tube, the short-net system compensation filter comprises a first transformer, the positive pole of the first transformer is connected to an ammeter, the output ends of the ammeter are respectively connected to a load electrical appliance and a filter, the positive and negative poles of the load electrical appliance are both provided with a short-net resistor, the positive pole of the ammeter and the short-net resistor and the negative pole of the first transformer and the short-net resistor are connected to the compensation device through a second transformer.

[0007] As a further solution of the utility model: an active and reactive power measuring device connected in parallel with the ammeter is installed on the line between the first transformer and the load electrical appliance.

[0008] As a further solution of the utility model: the positive and negative poles of the first transformer are respectively connected to a voltmeter and a display, and the voltmeter is connected in parallel with the load electrical appliance.

[0009] As a further solution of the utility model: a grounding wire is connected to the neutral line of the second transformer, and the neutral line of the first transformer is also connected to the grounding wire.

[0010] As a further solution of the utility model: the first transformer is also provided with an oscilloscope.

[0011] As a further solution of the utility model: the filter is provided with a compensation unit, which is composed of a three-pole switch, a fuse, a capacitor, a reactor and a load cable, and is respectively connected to the a and x terminals of the filter.

[0012] Compared with the prior art, the beneficial effects of the utility model are:

[0013] 1. The low-voltage compensation device of the submerged arc furnace adds a low-voltage reactive compensation device set of the submerged arc furnace short network, which reduces the primary current of the submerged arc furnace short network and greatly increases the active power, thereby greatly improving the operating parameters and consumption indicators of the submerged arc furnace, improving the smelting efficiency of the submerged arc furnace and reducing power consumption.

[0014] 2. The low-voltage compensation device of the ore-heating furnace adopts a hybrid filter combining a series active power filter and a passive filter to control the harmonic pollution of the ore-heating furnace according to the characteristics of passive filters and active filters and the harmonic characteristics of the ore-heating furnace itself, thereby reducing the probability of harmonic generation and ensuring the safety of the power grid, laying a technical foundation for the optimization of the secondary low-voltage short network of similar ore-heating furnaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of a compensation power path of a low-voltage compensation device for an electric arc furnace;

[0016] Figure 2 It is a schematic diagram of a short-net low-voltage filtering compensation energy-saving device of a submerged arc furnace in a low-voltage compensation device of a submerged arc furnace;

[0017] Figure 3 A schematic diagram of a compensation filter for a short-circuit network system in a low-voltage compensation device for an electric arc furnace;

[0018] Figure 4 A schematic diagram of a compensation filter for a short-circuit network system in a low-voltage compensation device for an electric arc furnace;

[0019] Figure 5 A schematic diagram of the branch boundary of a primary phase unit of a short-circuit network system compensation filter in a low-voltage compensation device for an electric arc furnace;

[0020] Figure 6 The present invention is a schematic diagram of the access principle of the compensation phase unit branch of the short network system in a low-voltage compensation device of an electric arc furnace.

[0021] In the figure: 1. Oscilloscope; 2. First transformer; 3. Ammeter; 4. Voltmeter; 5. Display; 6. Filter; 7. Compensation device; 8. Short-circuit resistor; 9. Load electrical appliances; 10. Second transformer; 11. Active and reactive power measurement equipment. DETAILED DESCRIPTION

[0022] See also Figures 1 to 6In the embodiment of the utility model, the low-voltage compensation device of the submerged arc furnace includes a power grid, a furnace transformer, a harmonic monitoring energy control device, a submerged arc furnace, a low-voltage filtering compensation and power-saving device for the submerged arc furnace, and a short-circuit system compensation filter arranged in the low-voltage filtering compensation and power-saving device for the submerged arc furnace. The power grid is connected to the furnace transformer, the furnace transformer is connected to the submerged arc furnace through the short-circuit, the furnace transformer is connected to the low-voltage filtering compensation and power-saving device for the submerged arc furnace through the harmonic monitoring energy control device, the low-voltage filtering compensation and power-saving device for the submerged arc furnace is connected to the short-circuit through a water-cooled copper pipe, and the short-circuit system compensation filter includes a first transformer 2, the positive pole of the first transformer 2 is connected to the ammeter 3, and the input of the ammeter 3 The output ends are connected to the load electrical appliance 9 and the filter 6 respectively. The positive and negative poles of the load electrical appliance 9 are both provided with a short-circuit resistor 8. The positive poles of the ammeter 3 and the short-circuit resistor 8 and the negative poles of the first transformer 2 and the short-circuit resistor 8 are connected to the compensation device 7 through the second transformer 10. The positive and negative poles of the first transformer 2 are respectively connected to the voltmeter 4 and the display 5. The voltmeter 4 is connected in parallel with the load electrical appliance 9. The secondary low-voltage compensation device uses a low-voltage self-healing power capacitor, uses an imported base film, adopts a silver-zinc coating, uses an aluminum alloy shell packaging, and has a built-in pressure cut-off explosion-proof device. It has the characteristics of low voltage, high current, and good self-healing characteristics. The first transformer 2 and the load An active and reactive power measuring device 11 connected in parallel with the ammeter 3 is installed on the line between the electrical appliances 9. In the design of the short-circuit side compensation system, capacitors are used for reactive power compensation to increase the power factor to above 0.75, and increase the active power output under the condition of reducing the primary side current. For possible harmonic currents, series filter reactors are installed to eliminate and absorb harmonics. Reactors of different ratios are installed to prevent surge currents and absorb the 3rd, 5th, and 7th harmonics, and isolate the 3rd harmonic. The signal collector uses a full-parameter power quality intelligent collector to collect all power quality parameters of the smelting system, including all electrical parameters of three-phase and single-phase This technology applies the original mature on-site compensation technology compatible with power filtering to the secondary low-voltage side of the ore-heating furnace, converts reactive power into active power and suppresses harmonic amplification, and directly transmits it to the vicinity of the copper tile side. At the same time, phase compensation is adopted to make the active power on the three-phase electrodes in the ore-heating furnace equal, so as to improve the power factor, reduce the imbalance of three-phase power and improve the index. It is a reliable user energy-saving technology. For example: the power factor of 25.5MVA ore-heating furnace smelting is relatively low, generally not exceeding 0.65, and dynamic control of short-network reactive power compensation is required to increase the power factor to above 0.75 quality assurance. The low-voltage compensation power path is shown in Figure 1The filter 6 is provided with a compensation unit, which is composed of a three-pole switch, a fuse, a capacitor, a reactor and a load cable, which are connected to the a and x terminals of the filter 6 respectively, to improve the utilization rate of the transformer and the high-current line, and to increase the effective input power of the smelting. For calcium carbide smelting, the generation of reactive power is mainly caused by arc current, short-circuit network and roadside power consumption. The compensation point is moved to the short-circuit network to compensate for the large amount of reactive power consumption of the short-circuit network on the spot, improve the output of the transformer, and increase the effective input power of the smelting. Due to the unbalanced arrangement of the three-phase short-circuit network and the smelting process, the self-inductance and mutual inductance generated after the current passes through are different, and the different voltage drops of the three phases are This leads to the formation of strong and weak phase phenomena. The melting power of the charge is a function of the electrode voltage and the charge specific resistance, which can be expressed as P=U2 / R. Starting from this basic point, at the point where the three-phase short network and the electrode are basically equal in length, single-phase parallel connection is used for reactive compensation. The compensation capacity of each phase is adjusted comprehensively to make the effective working voltage of the three-phase electrode tend to be consistent, balance the electrode voltage, and balance the three-phase charge consumption, thereby changing the strong and weak phase parallel connection of the three phases. After compensation, the smelting gear and the pole center circle and the reactive demand of constant power and constant current are adjusted according to the furnace conditions to expand the electrode operating area to achieve the purpose of increasing production and reducing consumption.

[0023] Reduce the value of high-order harmonics, reduce additional losses of transformers and networks, and improve the power quality of the system. High-order harmonics will be generated during smelting in electric furnaces, especially the 3rd, 5th, 7th, and 11th harmonics, which are the most serious. If they are not restricted and absorbed, they will have an adverse effect on both the equipment and the compensation device. Therefore, in the equipment, we will design the parallel filter capacitor and filter reactor into a filter circuit according to the harmonic conditions of the smelting. According to the formula:

[0024] Un=In(nX-X / n)-0Lc

[0025] Un-harmonic voltage; In-harmonic current; XL-reactor inductive reactance; XC-capacitor capacitive reactance. To reduce and absorb harmonics above nth order, the LC self-resonance frequency should be less than n. For the 3rd and 5th harmonics, we design the tuning frequencies to 134Hz and 189Hz respectively to absorb higher harmonics. Due to the on-site compensation, the higher harmonics generated during smelting can be absorbed by the L-C resonant circuit of the low-voltage reactive compensation system, instead of passing through the transformer and high-voltage network, thereby effectively reducing the higher harmonic value and reducing the additional loss of the transformer and short-circuit network.

[0026] The reactive power consumption of the ore-fired furnace is mainly in the transformer and short-circuit network. The implementation of low-voltage reactive power compensation can not only compensate the loss of the short-circuit network and transformer on site, but also compensate the loss of the high-voltage line. Therefore, compared with high-voltage compensation, the improvement of its power factor is effective for both the power grid system and the furnace. The connection path is shown in Figure 2 ;

[0027] Since the compensation capacity of the secondary low-voltage compensation device is relatively large and the operating voltage is low, its working current reaches several thousand amperes per phase branch. Therefore, the structure is a tray mode, and the installation and maintenance of the equipment are extremely convenient. The large and small units can be interchanged in each phase branch. At the same time, the compensation capacity can be appropriately adjusted when the relevant parameters allow;

[0028] The power-free capacity of the capacitor required for parallel compensation can be calculated by the following formula;

[0029] Q B-C =Q0-Q (1)

[0030] or Q BC =S0(sinø0-sinø) (2)

[0031] Q BC =S0cos ø0(tgø0-tgø) (3)

[0032] Q BC =P0(tgø0-tgø) (3)

[0033] or Q BC =3 I0 2 X-Ssin (4)

[0034] In the above formulas, the parameters before compensation are represented by codes with subscript "0", and the parameters after compensation are represented by codes without subscripts, but the inductive reactance in formula (4) is an exception. It should be represented by 0X with subscripts. Because the inductive reactance of the generalized short-circuit network converted into a star circuit remains basically unchanged before and after the reactive power compensation of the electric furnace is put into use, the inductive reactance is represented by X without subscripts for the sake of simplicity.

[0035] The short-circuit system compensation filter is set to a fifth filter QC = 6716KVAR, 30152A / 3, (5 channels per phase, 15 channels / unit for three phases),

[0036] A 25.5MVA / 148V-176-222V secondary low-voltage short-grid compensation filter device can be used. After it is put into use, the power factor on the short-grid side of the electric furnace can reach 0.75-0.78. The reduction of primary current has greatly increased the effective power, the short-grid measured voltage has increased by 3V-5V, and the power saving rate has reached more than 3%-4%, which has greatly improved the operating parameters and consumption indicators of the furnace.

[0037] In a preferred embodiment, a grounding wire is connected to the neutral line of the second transformer 10, and the neutral line of the first transformer 2 is also connected to the grounding wire.

[0038] In a preferred embodiment, the first transformer 2 is further provided with an oscilloscope 1 .

[0039] It should be noted that the above embodiments all belong to the same utility model concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference can be made to the description in other embodiments.

[0040] The above-mentioned embodiments only express the implementation methods of the utility model, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the utility model patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the utility model, and these all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A low-voltage compensation device for an ore-bearing furnace, comprising a power grid, a furnace transformer, a harmonic monitoring energy management and control device, an ore-bearing furnace, an ore-bearing furnace low-voltage filtering compensation and power-saving device, and a short-circuit system compensation filter arranged in the ore-bearing furnace low-voltage filtering compensation and power-saving device, wherein the power grid is connected to the furnace transformer, the furnace transformer is connected to the ore-bearing furnace through the short-circuit, the furnace transformer is connected to the ore-bearing furnace low-voltage filtering compensation and power-saving device through the harmonic monitoring energy management and control device, and the ore-bearing furnace low-voltage filtering compensation and power-saving device is connected to the short-circuit through a water-cooled copper tube, characterized in that: The short-circuit system compensation filter comprises a first transformer (2), the positive pole of the first transformer (2) is connected to an ammeter (3), the output end of the ammeter (3) is respectively connected to a load electrical appliance (9) and a filter (6), the positive and negative poles of the load electrical appliance (9) are both provided with a short-circuit resistor (8), and the positive poles of the ammeter (3) and the short-circuit resistor (8) and the negative poles of the first transformer (2) and the short-circuit resistor (8) are connected to a compensation device (7) via a second transformer (10).

2. The low-pressure compensation device for a submerged arc furnace according to claim 1, characterized in that: An active and reactive power measuring device (11) connected in parallel with the ammeter (3) is installed on the line between the first transformer (2) and the load electrical device (9).

3. The low-pressure compensation device for a submerged arc furnace according to claim 1 or 2, characterized in that: The positive and negative poles of the first transformer (2) are respectively connected to a voltmeter (4) and a display (5), and the voltmeter (4) is connected in parallel with a load electrical device (9).

4. The low-pressure compensation device for a submerged arc furnace according to claim 1, characterized in that: A grounding wire is connected to the neutral line of the second transformer (10), and the neutral line of the first transformer (2) is also connected to the grounding wire.

5. The low-pressure compensation device for a submerged arc furnace according to claim 1, characterized in that: The first transformer (2) is also provided with an oscilloscope (1).

6. The low-pressure compensation device for a submerged arc furnace according to claim 1, characterized in that: The filter (6) is internally provided with a compensation unit, which is composed of a three-pole switch, a fuse, a capacitor, a reactor and a load cable, and is respectively connected to the a and x terminals of the filter (6).

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