What is the role of the reactor?
Published time: 2019-07-04
Reactors are a very important electrical device and are widely used in power systems. With the continuous development of power systems, the performance requirements of reactors are getting higher and higher. In many power system situations, it is more desirable that the reactance values of reactors can be adjusted or controlled according to actual needs.
What is the role of the reactor?
There are several types of reactors that have different effects. A reactor is connected in series in the circuit to increase the loop impedance and reduce the short-circuit current in the event of an accident. It is widely used in circuits below 10KV. One is a shunt reactor, which acts to transmit the inductor current of the power grid, and is generally used in a transmission circuit of more than 330KV. Due to the high voltage of the high-voltage and ultra-high-voltage transmission lines, the capacitance effect of the line is also high. If the inductance is not supplemented to offset the capacitance effect, high voltage will be caused in the middle of the line due to the capacitance effect, which jeopardizes the line insulation. Another type is used to form a resonant circuit with a capacitive element. The capacitor is connected in parallel with the reactor. If the parameters are properly matched, a certain frequency will be resonated, so that the voltage of the resonant wave appears on the parallel circuit. The voltage is drawn to obtain a signal of a certain band. Generally used for long-distance signal transmission.
The use of reactors in the rectification loop where AC changes to DC has two functions. One is to reduce the short-circuit current level of the loop. The main thing is to use the reactor to have a characteristic that the current cannot be abrupt, and other components in the loop (capacitors) Or resistance), to play the role of leveling DC fluctuations.
1，The role of shunt reactor
It has many functions that can change and improve the reactive power related operating status of power system, and is often used in reactive power compensation. Simply speaking, the reactor can improve the voltage distribution on the long transmission line, and can realize the charging capacitive reactive power in the absorption cable line, and the reactor can effectively prevent the self-excitation when the generator has a long line. This resonance phenomenon.
2, the role of the series reactor
in general, it is mainly used to limit the short-circuit current, not only that, but also in the filter and capacitors in series or parallel, which can limit the production in the grid Higher harmonics, in fact, series reactors are used to limit current.
3, the role of DC reactor
usually installed in the frequency conversion system between the DC rectifier link and the inverter link between the two units, the main purpose is to be able to limit the AC component superimposed on the DC current to a specified value The current can ensure the continuity of the rectified current and reduce the current pulse value, so that the DC reactor can make the operation of the inverter link more reliable and stable, and at the same time improve the power factor of the inverter.
4, the role of the input reactor
mainly used to limit the sudden change of voltage in the power grid or the current impact phenomenon when operating overvoltage, and also when the smoothing power supply voltage such as spikes, smooth bridge rectifier circuit When the phase causes voltage defects, etc., the input reactor can effectively protect the frequency converter and improve the power factor, and can prevent interference from the power grid while reducing the pollution of the harmonic current generated by the rectifier unit to the power grid.
5, the role of the output reactor
can play the compensation line is the part of the capacitance of 50 meters to 200 meters, but also suppress the output harmonic current to improve the output high frequency resistance, and suppress DV / DT reduce high frequency Leakage protects the frequency converter and reduces equipment noise. When the reactor is in the state of compensating power, it is usually subject to impact from harmonic voltage and current, resulting in capacitor damage and power factor reduction, so it is necessary to control the harmonics during compensation.
6, the role of current-limiting reactor
relatively speaking, it is much simpler, mainly used in the power system, when the fault occurs, it will limit the feeder over-current (specifically, as shown in the figure below).
7，The role of the smoothing reactor
It is a very important component for the rectifier circuit. It is mainly used to limit the short-circuit current when used in the intermediate frequency power supply. That is to say, when the inverter thyristor is performing the commutation At the same time, the conduction is equivalent to the short-circuit fault of the rectifier bridge load. Therefore, if there is no reactor, it will be directly short-circuited, and the effect of suppressing the intermediate frequency component on the power frequency grid can be suppressed.
The filtering function is that when the rectified current has an alternating current component, the high-frequency alternating current is different, and after a large inductance causes the rectified output waveform to be continuous or intermittent, a current time of zero occurs, and the inverter bridge at this time occurs. Then immediately stop working and cause the rectifier bridge to open. The input power of the parallel inverter circuit has the throughput of the reactive component. Therefore, the reactor of the inverter bridge must have a reactor with the effect of energy storage.
8,The role of the inverter reactor
This type of reactor is generally installed on the DC converter input of the inverter or the output terminal, mainly to suppress the three to five harmonics generated by the inverter. Waves transmit motion to the grid, and reduce the interference of harmonics caused by frequency conversion on other components, while improving the stability of the overall grid and improving the power factor, and can also limit the abnormal fluctuation of the grid voltage and the impact on the grid. Current, smooth waveform, reduce the impact on the inverter.
In addition to the above, the inverter reactor has several important functions: firstly, it can achieve the capacitive effect on the light load or the light load line, which leads to the reduction of the transient overvoltage phenomenon of the power frequency. Secondly, it can improve the voltage distribution on the transmission line and prevent the self-excited resonance phenomenon of the generator with a certain probability of long lines. Finally, the reactor can be used to balance the reactive power in the line as lightly as possible, while preventing the occurrence of improper flow of reactive power and reducing the excessive power loss on the line.
9,The role of the filter reactor
This reactor is often widely used in high and low voltage filter cabinets. When installed, it will be connected in series with the filter capacitor, and tuned to a certain resonant frequency to absorb the grid. The corresponding frequency harmonic currents appear in the process, as well as the elimination of higher harmonics for the main transformer or other electrical equipment components of the system. Filter reactors mainly play a role in absorbing power grid harmonics, improving system power factor and safety.
The main functions of the reactor are as follows:
1. Capacitance effect on light airborne or lightly loaded lines to reduce power frequency transient overvoltage;
2. Improve the voltage distribution on long-distance transmission lines;
3. Make the reactive power in the line as light as possible on the light load, prevent the irrational flow of reactive power and reduce the power loss on the line;
4. When the large unit is in parallel with the system, reduce the steady-state voltage of the power frequency on the high-voltage bus, so that the generators can be juxtaposed;
5. Prevent self-excited resonance phenomenon that may occur in generators with long lines;
6. When the neutral point of the reactor is used to pass the small reactance grounding device, the small reactor can also be used to compensate the phase and phase capacitance of the line to accelerate the automatic extinguishing of the submersible current, which is convenient to adopt.
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