With the development of steel industry and smelting technology, more and more into the production of electric arc furnace equipment, its capacity is more and more big. Due to its own operating characteristics, the problem is becoming more and more serious harmonic pollution, the serious influence to the power quality, harmonic governance is imminent.
One, the basic overview
Electric arc furnace is generally three phase type, through the special arc furnace transformer power supply, transformer high voltage side usually is 6.3 KV, 10 KV, 35 KV, 110 KV, low voltage side is usually more than one hundred v to one thousand v. At present commonly used arc furnace specification mainly between the furnace 2 t to 100 t.
Electric arc furnace is a nonlinear load, in the process of work will produce higher harmonic, power consumption is very big, and electric furnace furnace transformer capacity from megavolt ampere to dozens of megavolt ampere. From the points of steel and iron smelting process, the working process of the electric arc furnace can be divided into three phases: the melting period, oxidation period and reduction period. Steel in melting period of power consumption is very big, oxidation period and reduction period of power consumption is decreased obviously. Steel during the melting period of arc furnace power consumption not only is the largest, and at this stage due to drop electrode arc starting and burden collapses electrode contact scrap the short circuit, followed by rapid ascension electrode and snap arc circuit, produce very big during the period of short circuit current, three-phase imbalance. In the smelting process due to the electromagnetic force and the effect of air flow in the furnace and the flow of molten steel and slag, make the arc discharge path changing and changing arc gap ionization degree, leading to changes in load current frequent change big, fast changes, and no rules. Melting period due to a large number of solid not molten material, the furnace state is not stable, then irregular current waveform, harmonic content, mainly is 2, 3, 4, 5, 6, 7, such as relatively low harmonic wave and contains a lot of rich gap voltage fluctuation and flicker, lead to the distortion of grid voltage and current. Refining period stable electric arc furnace, the harmonic content is not big.
Harmonic filter is suppress harmonic voltage and harmonic current distortion is one of the main way. Currently KYSVC high-pressure static type dynamic reactive power compensation device is the most mature technology of electric arc furnace harmonic governance.