The reactance caused by the short network of large and medium submerged arc furnaces accounts for about 70% of the operating reactance of the heating furnace. The submerged arc furnace short network refers to the general term for various forms of low pressure and high current electrical conductors from the low group outlet end of the electric furnace transformer to the electric stage. Although the length of the short net of the submerged arc furnace is not large, the short net resistors and reactances have a great impact on the equipment of the submerged arc furnace. Due to its cumbersome structure, the current passing through it reaches hundreds of thousands of amperes. Because the short-circuit reactance value is generally 3 to 6 times that of the resistor, the short-circuit reactance largely determines the efficiency, power factor and energy consumption level of the submerged arc furnace.
The common manual compensation method is to connect the series compensation capacitor bank to the high-voltage bus on the primary side of the submerged arc furnace transformer, that is, high-voltage compensation. Since the compensation effect can only benefit from the line before the access point and the power grid side of the power supply system, the power supply system can meet the requirements related to the power factor of the load line, but cannot compensate for the transformer windings, short network, and electrodes of the mine furnace. The reactive power of all secondary-side low-voltage and high-current circuits, that is, the equipment cannot benefit from the increase in the production of mine furnace products and the reduction in power consumption and mine consumption.
Generally, positioning harmonic countermeasures and concentrated harmonic countermeasures can be combined to form a cost-effective harmonic countermeasure. For harmonic source loads with large power (such as frequency furnaces, inverters, etc.), harmonic countermeasures can be used for positioning harmonic countermeasures , to reduce the harmonic current injected into the grid. Relatively small power and scattered nonlinear loads can be managed uniformly on the bus. Hongyan APF active filter can be used, and harmonic control can also be used.
The submerged arc furnace is a high energy consumption electric melting furnace with the characteristics of a resistor electric arc furnace. The power factor is determined by the arc and resistance R in the furnace and the value of resistance R and reactance X in the power supply circuit (including transformers, short-circuit nets, collector rings, conductive jaws and electrodes).
cosφ=(r #+r)/resistance x value of resistor r generally does not change when the submerged arc furnace is in operation, they depend on the design and installation of short network and electric stage layout. The resistance R is related to the current intensity of the short-circuit upstream components during the operation process, and the change is not large, but the resistance R is an important factor in determining the power factor of the submerged arc furnace during the operation process.
Since the submerged arc furnace has weaker resistance than other electric smelting furnaces, its power factor is also reduced accordingly. In addition to the natural power rate of the general small mine furnace reaching above 0.9, the natural power rate of the large mine furnace with a capacity above 10000KVA is all below 0.9, and the larger the capacity of the mine furnace, the lower the power factor. This is due to the larger inductive load of the submerged arc furnace transformer in a large space, the longer the short network, and the heavier the waste material inserted into the furnace, which increases the reactance of the short network, thereby reducing the power factor of the submerged arc furnace.
In order to reduce power grid consumption and improve the quality of the power supply system, the Power Supply Bureau stipulates that the power factor of the power company should be around 0.9, otherwise the power company will be punished with huge penalties. In addition, the low power factor will also reduce the incoming line voltage of the submerged arc furnace, which will harm the calcium carbide smelter. Therefore, at present, large-capacity submerged arc furnaces at home and abroad need to install reactive power compensation devices to improve the power factor of submerged arc furnaces.
Low voltage filter compensation
1. Principle
Low-voltage compensation is an ineffective compensation device that uses modern control technology and short-network technology to connect large-capacity, high-current ultra-low voltage power capacity to the secondary side of the mine furnace. This device is not only the best performance of the principle of reactive power compensation, but also can make the power factor of the mine furnace run at a higher value, reduce the reactive power consumption of the short network and the primary side, and remove the third, fifth and seventh harmonics. Balance the three-phase output power to increase the output capacity of the transformer. The focus of control is to reduce the unbalanced degree of three-phase power and achieve equal three-phase power. Expand the clamp pot, concentrate the heat, increase the temperature of the furnace surface, and speed up the reaction, so as to achieve the purpose of improving product quality, reducing consumption, and increasing production.
This technology applies the traditional mature on-site compensation technology to the secondary low-voltage side of the mine furnace. The reactive power generated by the capacitor passes through the short line, part of which is absorbed by the mine furnace transformer from the system, and the other part compensates for the reactive power of the mine furnace transformer, short network and electrodes. Power loss increases the active power input into the furnace. At the same time, phase-separated compensation is adopted to make the active power on the three-phase electrodes of the submerged arc furnace equal, so as to improve the power factor, reduce the unbalance of three-phase power, and improve the production index.
2. Application of low voltage compensation
In recent years, due to the gradual improvement of low-voltage compensation technology, the design scheme has become more and more perfect, and the volume has been greatly reduced. Submerged arc furnace manufacturers have also learned about its performance in improving the economic benefits of submerged arc furnaces. Low-voltage compensation equipment has been widely used in Submerged arc furnace transformer.
Solutions to choose from:
plan 1
Use high-voltage filter compensation (this scenario is a common compensation, but the actual effect does not meet the design requirements).
Scenario 2
On the low-voltage side, dynamic three-phase fractional compensation filter compensation is adopted. After the filter device is put into operation, the active power on the three-phase electrodes of the submerged arc furnace is equalized, so as to improve the power factor, reduce the unbalance of three-phase power, and improve the production index.
Post time: Apr-13-2023