In the actual production, the normal production of generators and blast furnaces is restricted by wind, gas, water gas and electricity. The generator is not only the key equipment of the blast furnace power supply system, but also the energy-saving equipment of the blast furnace production. When the power is lost or the voltage fluctuates, the whole furnace power supply system will be paralyzed, and the load will be dragged from the generator to the outside, which will drag the generator and cause the factory to lose power. It can be seen that perfecting the protection of the generator so that the generator can still operate normally after the sudden loss of power of the external power grid becomes the key to solving the power failure of the furnace.

The overall design principle: the phenomenon that the plant or power plant running in parallel is out of synchronization is called oscillation, and the angle between the equivalent potentials on both sides of the power system is periodically changing. There are many reasons for the oscillation of the system. Most of them are caused by the system's transient stability damage due to the long time of resolving the fault. In the weakly connected system, it may also be due to misoperation, generator loss of magnetism or fault trip, disconnection. System or device causes the system to oscillate. After the power system oscillates, it may be restored by the action of the excitation regulator or the automatic device. If necessary, the oscillating power system can be disengaged at the predetermined disconnection point, the unit in the power plant with excess power is cut off, or some These loads are used to restore the system to stable operation as soon as possible.

The original protection device and its original protection device are: 1 The network switch of the generator and the external power grid is equipped with directional overcurrent protection. When the external power grid fails, the protection circuit acts to cut off the power grid; 2 The generator itself has overcurrent and over Pressure and low voltage protection measures; 3 Formulating rules and measures to manually remove the network switch, carry out self-protection power generation, and avoid power failure caused by lightning strikes on the network line. However, these protection devices and measures can only effectively protect the generator, the main transformer, etc., and the problem that the generator is dragged when the external power grid suddenly loses power and the internal power grid is struck by lightning cannot be solved. The reason is as follows: When the external power grid is faulty, first, even if the upper-stage pressure-relief station has been disconnected, other equipment on the line connected to the generator and the line and the fault point still need to pull the load from the generator, resulting in voltage, The frequency drops sharply, the overcurrent is formed, and the generator is dragged. Second, even if the networked switch protection component cuts off the external power grid in time, the generator suddenly changes from heavy load to light load, the speed increases sharply, and the voltage rises, causing the flying car. Causes the generator protection component to trip and stop; the third is that during the operation of the generator, the offset of the protection technical parameters of the equipment will cause the generator to trip prematurely. If the setting value of the voltage relay is too high, the generator voltage will drop. Leading to premature action and tripping; fourth is the weather conditions during the thunderstorm season. Although the network can self-protect the power generation, but the defects are many, the generator and the external power grid cannot be connected to the grid and the power supply is not safe. In addition, the low-voltage power inside the factory The AC contactor supply voltage in the electrical circuit of the device trips when it is less than 85% of the rated voltage.

Improve the protection device and technical parameters to solve the problem that the generator is dragged by external and internal electricity. The technology should be improved on the original basis: the QFK central control system (referred to as the central control) is used to protect the generator, which has automatic Net, net, load shedding and balancing load functions. After the introduction of the central control, the technical parameters matched with the generator are selected according to the actual situation, so that when the external power grid suddenly loses power, the external power grid can be effectively removed within the set time, the load can be balanced, and the generator can be operated according to the generator. In the case, the generator is automatically deloaded. “Central Control” can operate the network in time when the external power grid loses power, but the generator and the network switch and the load shedding switch are simultaneously tripped, which is not allowed. Through the adjustment of the original technical parameters of "Central Control", the needs of generator operation are met. The modified "central control" works well with the generator. Below is a brief block diagram of the central control system. The block diagram of the central console and the conditions that each component should meet determine the magnitude and direction of the differential pressure of the grid-connected device load balance test. When the differential pressure frequency is not met, the lock-close command is issued. At 5 Hz, the speed-increasing pulse (issued at 0~180.) automatically sends different numbers of pulses according to the frequency difference within a certain time. In order to adapt to different adjustment mechanisms, the pulse width should be adjustable (0.1-0.4s). The slip is too large or too small. Both should send multiple pulses. The pressure pulse interval can be in the range of 3 ~ 6s. When the grid is connected, the two power supply voltages, that is, 360V 矣U, 400V, the voltage conditions are satisfied. At the same time, the frequency difference is very high, and the condition should be met: =N3, fuzzy decision is made, the values ​​of N, team and N3 are adjusted appropriately to reduce the error of closing, and to avoid the opportunity of closing. At the same time, it is detected that the phase angle 150' of the two power grids is closed and the latching relay B is closed, and the program starts running.

(2) The automatic disengagement device of the disengagement device is set at the disengagement point, the reaction system oscillates and operates, and the system is disassembled at the predetermined disassembly point, which is an effective measure taken to prevent the accident from continuing to expand after the power system loses stability. one. Power plants or local power systems with roughly balanced loads are listed from the system to ensure the normal operation of the local system, while other measures are still taken to control the accidents in local areas to prevent accidents from expanding.

If the voltage or frequency of the system continues to drop after the system is disconnected from the grid, there is a possibility of voltage collapse or frequency collapse. By monitoring the voltage and frequency of the system by the single-chip microcomputer, when the voltage or frequency of the system continues to decrease after the disengagement command is issued, the automatic low-week grading load shedding is adopted, and the first, second and third stage load shedding commands are issued hierarchically, and some secondary cuts are performed. Load, to ensure the continued safe operation of the system. The requirements that the automatic de-column device should meet should accurately distinguish between short-circuit faults and system oscillations. The execution command shall be issued when the system starts to oscillate, that is, when the angle between the two sides of the potential is just turned on, or the execution command is issued during the first oscillation period in which the stability has been destroyed. It should be possible to determine whether the unit on the installation side of the unit is at the speed of opening or decelerating in order to issue different execution commands according to different requirements. After the power grid signal and generator signal sent by the transformer are processed by “central control”, it is decided whether to balance the load and load load shedding. When the external power grid loses power or voltage fluctuation, the signal is sent from the PT to the “central control”. In other words, when the frequency of the power grid drops to 4S.8HZ or the voltage drops to 85% of the rated voltage, the central control "acts to turn on the network switch. After 0.3 seconds, the external power grid is cut off, and the generator is self-protected. If the two generators are fully loaded, the "central control" will send a balance signal according to the load condition, and turn on the turbine speed regulating motor to balance the power generation; if the power generated by the two generators is less than 4400KW, two The generator can not afford the entire load and needs to be deloaded.

Improve the control circuit of important pumps and fans The waste heat generator uses blast furnace gas as energy source. For furnaces and generators as well as the whole system, electricity, water and gas are highly cyclic and interdependent. This problem is more prominent after the power outage of the external power grid, which will cause the furnace to be shut down and the whole plant to stop production. The generator shutdown is caused by the normal tripping of the AC contactor of the pump motor. Therefore, a relatively complete control circuit is designed. On the basis of the original circuit, a heavy hammer connecting rod and a traction electromagnet are added to make the The circuit not only maintains the original function but also does not trip when the power grid loses pressure. The attracting coil is normally not energized, and the contactor is locked by the heavy hammer link. Overcoming the problem of the release of the power grid and the loss of electrical contactor, the circuit was installed on thirteen important pumps and fans with good results.

Conclusion: This paper discusses the measures for normal power generation and normal operation of the furnace when the external power grid of the factory is out of power, and discusses the limitations of the original equipment and the working principle of the newly introduced equipment and the corresponding control circuit, thus solving the troubled factory. A major problem in power supply has high theoretical value and practical value.

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