Reactors used in power systems are usually series reactors and shunt reactors.
Series reactor is mainly used to limit the short-circuit current, but also in the filter with capacitors in series or in parallel to limit the higher harmonics in the power grid. Reactors in 220kV, 110kV, 35kV, 10kV grids are used to absorb the capacitive charge of the cable lines. The operating voltage can be adjusted by adjusting the number of shunt reactors. EHV shunt reactors have several functions that improve the reactive power of the power system in relation to operating conditions, including:
1, light-load or light-load capacitive effect on the line to reduce power frequency transient over-voltage;
2, to improve the voltage distribution on long transmission lines;
3, the light load when the line reactive power as far as possible on-site balance to prevent unreasonable flow of reactive power but also reduce the power loss on the line;
4, in large units and systems tied to reduce high-voltage bus voltage on the steady-state voltage, to facilitate the generator side by side over the same period;
5, to prevent the generator with long lines possible self-excitation resonance;
6, when the reactor neutral point through the small reactance grounding device,
Small reactors can also be used to compensate for the phase-to-phase and phase-to-ground capacitors to speed up the sub-current automatically extinguished, easy to use.
Reactor wiring in series and parallel in two ways. Series reactors usually function as current limiters, and shunt reactors are often used for reactive power compensation.
1, semi-core dry shunt reactor: In the EHV long distance transmission system, connected to the transformer on the three coils. It is used to compensate the capacitive charging current of the line, to limit the system voltage increase and over-voltage operation, and to ensure the reliable operation of the line.
2, half-core dry-type series reactor: installed in the capacitor circuit, the capacitor circuit in time.
Reactor current limiting and filtering:
The expansion of grid capacity makes the rating of system short circuit capacity rapidly increase.
For example, in the low-voltage 35kV substation of 500kV substation, the maximum effective value of three-phase symmetrical short-circuit current is already close to 50kA. In order to limit the short-circuit current of the transmission line and protect the electric equipment, a reactor must be installed, which can reduce the short-circuit current and keep the voltage of the short-circuit system unchanged.
Damping reactors (ie, series reactors) are installed in the capacitor circuit, and the inrush current is suppressed when the capacitor circuit is put into operation. At the same time with the capacitor bank to form a harmonic loop, from the harmonic effect of the filter. For example, in a capacitor circuit of a 35kV reactive power compensation device in a 500kV substation, a damping reactor must be installed in a 35kV capacitor circuit to restrain the 3rd harmonic in order to limit inrush current during capacitor input and to suppress high harmonics in the power system , With a rated voltage of 35kV, the rated inductance of 26.2mH, rated current of 350A dry hollow single-phase damping reactor damping, which 2.52Mvar capacitors on the 3rd harmonic resonant circuit, the third harmonic filter loop.
Similarly, in order to suppress the 5th and higher harmonics, a rated voltage of 35kV, the rated inductance of 9.2mH, 382A rated current single-phase outdoor damping reactor, which 2.52Mvar capacitor with 5 times and above higher harmonics Form a resonant circuit. Played a role in suppressing higher harmonics, it should be noted that in the national standard "reactor" GB10229-88 and IEC289-88 international standards are on the use of damping reactors and technical conditions are provided. But at present, some departments in China regard damped reactors as series reactors, strictly speaking, inappropriate, because none of the above standards have the name of series reactors.
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