The reactor used in power grid is essentially a hollow coil without magnetic materials. It can be arranged vertically, horizontally and three forms of assembly according to needs. When the power system is short circuited, it will generate large numerical short-circuit current. If not restricted, it is very difficult to maintain the dynamic stability and thermal stability of electrical equipment. Therefore, in order to meet the requirements of the interrupting capacity of some circuit breakers, the reactor is always connected at the outlet circuit breaker, increasing the short-circuit impedance and limiting the short-circuit current.
Because of the use of reactor, the voltage drop on the reactor is larger when a short circuit is short circuited, so it also plays the role of maintaining the voltage level of the bus, which makes the voltage fluctuation on the busbar less, and ensures the stability of the operation of the electrical equipment on the non fault line.
In recent years, in the power system, in order to eliminate the fault of capacitor caused by high order harmonic voltage and current, the series reactor is used to change the system parameters in the circuit of the capacitor, and the remarkable effect has been achieved.
The working principle of the reactor:
220kV, 110kV, 35kV and 10kV reactors are used to absorb capacitive reactive power in cable lines. The operation voltage can be adjusted by adjusting the number of shunt reactors. The UHV shunt reactor has many functions to improve the operation status of power system reactive power, including: (1) the capacitance effect on light load or light load line to reduce power frequency transient overvoltage. (2) to improve the voltage distribution on the long transmission line. (3) balance the reactive power in the circuit as far as possible in light load, prevent reactive power from flowing unreasonable, and reduce power loss on line as well. (4) reduce the power frequency steady-state voltage on the high-voltage bus when the large unit is parallel to the system, so that it is convenient for generators to be juxtaposed at the same time. (5) to prevent the self excitation resonance generator with long lines possible. (6) when the neutral point of reactor is used by the small reactance grounding device, a small reactor can be used to compensate the interphase and phase capacitance, so as to accelerate the automatic extinguishing of the submersible current and be easy to adopt.
Depending on the coil current changes of electrical impedance block. It is divided into 7 types by use: (1) current limiting reactor. It is connected in series in power circuit to limit the value of short-circuit current. 2. Shunt reactor.  Generally, it is reactive power compensation between the terminal and the earth of EHV transmission line. (3) communication reactor. It is also called a wave blocking device. It is used to block the carrier signal and transmit it into the receiving equipment. (4) arc suppression reactor. Also called arc suppression coil. Between the neutral point and the ground of the three-phase transformer, it is used to supply the electrical inductive current in the one phase connection of the three-phase power grid to compensate for the capacitive current flowing through the connection place, so that the arc is not easy to ignite, thus eliminating the overvoltage caused by the repeated reburning of the arc. (5) filter reactor. It is used in rectifying circuits to reduce the amplitude of the ripple current on the bamboo flow and to form a circuit that resonate with a capacitor to a certain frequency to eliminate the voltage or current of a certain harmonic in the electric circuit. The electric furnace reactor. It is connected with electric furnace transformer in series to limit its short-circuit current. The starting reactor.  In series with the motor, the starting current is limited.