The common reactors used in power system are series reactors and shunt reactors. Series-connected reactors are mainly used to limit short-circuit current, and also in series or parallel with capacitors in filters to limit higher harmonics in the power grid. The reactors in the 220kV, 110kV, 35kV and 10kV power grids are used to absorb the charge capacitive reactive power of the cable lines. The operating voltage can be adjusted by adjusting the number of shunt reactors. The UHV parallel reactor has a variety of functions to improve the reactive power operation of the power system, including:
1, light no-load or light load line capacitance effect, to reduce the power frequency transient overvoltage;
2. Improve voltage distribution on long transmission lines;
3, make the reactive power in light load line balance as far as possible, prevent the irrational flow of reactive power and reduce the power loss on the line;
4, when the large unit is juxtaposed with the system, the steady-state voltage of the power frequency on the high voltage bus is reduced, which is convenient for the generator to be juxtaposed at the same time;
5, prevent the generator with a long line may appear self-excitation resonance phenomenon;
6. When the neutral point of the reactor is used through the small reactance earthing device, the small reactor can also be used to compensate the line phase-to-phase and phase-to-ground capacitance to accelerate the automatic extinction of the latent power supply current, which is easy to use.
The wiring of reactor is divided into series and parallel two ways. Series reactors usually act as current limiting, and shunt reactors are often used for reactive power compensation.
1, half core dry shunt reactor: in the ultra-high voltage long-distance transmission system, connected to the transformer on the tertiary coil. It is used to compensate the capacitive charging current of the line, limit the system voltage rise and operating overvoltage, and ensure the reliable operation of the line.
2, half core dry series reactor: installed in the capacitor circuit, in the capacitor circuit input from.
Current limiting and filtering function of reactor:
With the expansion of power network capacity, the rating of system short-circuit capacity increases rapidly. For example, in the low-voltage 35kV side of the 500kV substation, the maximum three-phase symmetric short-circuit current effective value has been close to 50kA. In order to limit the short circuit current of the transmission line and protect the power equipment, the reactor must be installed. The reactor can reduce the short circuit current and keep the voltage of the system constant at the moment of short circuit.
A damped reactor (i.e. series reactor) is installed in the capacitor loop to inhibit inrush current when the capacitor loop is put in. At the same time, the harmonic circuit is formed together with the capacitor bank to filter each harmonic. For example, in the capacitor circuit of 35kV reactive power compensation device in 500kV substation, in order to limit the inrush current when the capacitor is put in and restrain the higher harmonics of the power system, the damping reactor must be installed in the 35kV capacitor circuit. When the third harmonic is suppressed, the rated voltage is 35kV and the rated inductance is 26.2mH. Rated current 350A dry hollow single-phase outdoor type damping reactor, it and 2.52Mvar capacitor to the third harmonic resonance loop, that is, the third harmonic filtering loop.
Similarly, in order to suppress the fifth or more higher harmonics, a single-phase outdoor resistive reactor with rated voltage of 35kV, rated inductance of 9.2mH and rated current of 382A is used. It forms a resonant loop with a 2.52Mvar capacitor to the fifth or more higher harmonics. Has played a role in the suppression of high harmonics, it needs to be explained that in the national standard "reactor" GB10229-88 and IEC289-88 international standards for the use of the damping reactor and technical conditions have made provisions. But at present some domestic departments will be damped reactor called series reactor, strictly speaking is not appropriate, because there is no series reactor this name in the above standards.