Characteristics of parallel reactors

1. Weaken the power frequency voltage rise caused by the capacitance effect of the line during no-load or light load periods.
(1) This voltage rise is caused by the voltage drop across the inductance of the line due to the capacitance (ground capacitance and phase to phase capacitance) current of the line under no-load or light load. It will cause the line voltage to be higher than the power supply voltage. When the situation becomes more severe, usually the longer the line, the greater the capacitance effect and the greater the increase in power frequency voltage.
(2) For ultra-high voltage long-distance transmission lines, the charging power of the line capacitor is very high when unloaded or lightly loaded. Usually, the charging power increases sharply with the square of the voltage. The huge charging power not only causes the above phenomenon of power frequency voltage rise, but also increases the power and energy loss of the line, as well as causing self excitation and synchronization difficulties. Installing parallel reactors can compensate for this charging power.
2. Improve the voltage distribution along the line and the reactive power distribution in light load lines, and reduce line losses.
When the power transmitted on the line is not equal to the natural power, the voltage at various points along the line will deviate from the rated value, sometimes even significantly. If compensation is relied on by parallel reactors, the line voltage can be lowered and increased.
3. Reduce the secondary current, accelerate the extinguishing of the secondary arc, and improve the success rate of automatic circuit reclosing.
(1) The so-called secondary current refers to the residual current present in the arc light at the fault point after the fault phase is disconnected on both sides when a single-phase instantaneous grounding fault occurs.
(2) The reason for the generation of secondary current: Although the fault phase is cut off from the power supply, the non fault phase is still running with electricity. Through the influence of phase to phase capacitance, the two phases provide capacitive power supply to the fault point; Due to the influence of mutual inductance between phases, a potential will be induced on the faulty phase. Under the action of this potential, a circulating current will be formed through the fault point and the relative ground capacitance. The sum of the two currents is usually referred to as the secondary current. The existence of secondary current makes it impossible for the secondary arc at the point of single-phase instantaneous grounding short circuit in the system to extinguish quickly, which will affect the success rate of single-phase automatic comprehensive circuit breaker.
(3) The neutral point of the parallel reactor is compensated for the secondary arc current by grounding it with a small impedance, thereby accelerating the extinguishing of the secondary arc.
4. It is beneficial to eliminate the self excitation of the generator.
When a synchronous generator is loaded with a capacitive load (no-load or light load operation of a long-distance transmission line), the voltage of the generator will spontaneously establish and not correspond to the excitation current of the generator, that is, the generator will self excite. At this time, the system voltage will rise. By connecting a parallel reactor on a long-distance high-voltage line, the output impedance of the generator terminal on the line can be changed, effectively preventing the generator from self exciting.
5. Improve the power factor of the power grid.