Line Reactor, How it Works?
The line reactor is the general name of the inductor and the reactance device. As inductor appeared earlier on the history of electrical equipment and was called line reactor, capacitor is also called reactance device. Common line reactors include the incoming line reactor, which is used to restrict the sudden voltage change and current impact caused by overvoltage. It can also smooth the spike pulse contained in the power supply voltage, thus improving power quality. Single phase DC line reactor is mainly used between the DC link and link in the inverter system, its main function is to limit the AC component superimposed on the DC current to a specified value.
A conductor will produce magnetic field in a certain range of space it occupies when it's powered on, so all electric conductors carrying current are inductive on a general sense. However, a long straight conductor often generates a small inductance, the generated magnetic field is not strong, so the actual line reactor is a wire wound solenoid, which is also called air core line reactor. Sometimes an iron core would be inserted into the solenoid to generate greater inductance, which is called iron core line reactor. Reactance is divided into inductive reactance and capacitive reactance, in the more scientific division, both impedor (inductor) and reactance (capacitor) are called line reactor. However, as inductor appeared earlier and was called line reactor, the capacitor people often say only refers to the reactance, and line reactor refers specifically to the inductor. Main function of three-phase output line reactor is to compensate the influence of long line distributed capacitance, restrict the output of harmonic current and improve output high frequency impedance, thus protecting the inverter.
Common line reactors include the core-type line reactor. Such a line reactor has small size and low magnetic flux leakage, loss. It can be used in the high-voltage board. However, it also has many disadvantages, such as large noise, easy magnetic saturation (which may lead to burn out of coil), poor harmonic suppression and poor short circuit current resistant. Dry-type air core line reactor has strong flow capacity, simple but tough mechanical structure, it can be used outside. However, it has disadvantages of high active power loss and large electromagnetic interference to surrounding electrical equipment . Moreover, half core-type line reactor and magnetic shielding line reactor are also common. Therefore, the converter has many types and functions, proper line reactors shall be selected by demands in actual power systems.
line reactors used in power grids are actually air-core coils without magnetic material. It can be arranged vertically, horizontally and triangle according to needs. When the power system is short circuited, a large short circuit currents will be generated, if this current is not limited, it will be difficult to maintain the dynamic stability and thermal stability of electrical equipment. Therefore, in order to meet the requirements of interrupting capacity of some circuit breakers, line reactors are often connected in series at the breakers to increase the short circuit impedance and restrict short-circuit current. Due to the line reactor, the voltage drop on the line reactor is larger when the short circuit occurs, so it also maintains the voltage on the busbar, ensures a stable operation of electrical equipment on normal branches.