SVC Application Fields
A complete set of static VAR compensator (SVC) system can be used to generate varied inductive and capacitive reactive power quickly and constantly. So far, SVC system has been extensively used in electric power system and industrial field.
1. Hoists and Other Heavy Industrial Loads
The hoists and other heavy industrial loads may cause the following effects on the power grid when they are at working state
a. Voltage drop and voltage fluctuation in the power grid;
b. Low power factor;
c. High-order harmonics
Our SVC can perfectly solve the above problems and help customers obtain the following benefits:
a. Increase the power factor by dynamic reactive power compensation
b. Eliminate the voltage distortion caused by harmonic
c. Stabilize the voltage and reduce the voltage fluctuation and flicker
d. Balance the three-phase load current and eliminate the negative sequence current
e. Increase the operation safety of the impact loading equipment and its adjacent electrical equipment
2. Long Distance Power Transmission
In the case of long-distance AC transmission, due to the influence of Ferranti Effect, the voltage will rise along the transmission lines which will limit the transferred power. The capacitive power along the long distance power transmission line is in proportion to the cable length and the square of voltage. This results in the voltage rising of 1.5 to 2 times of rated voltage at the end of the transmission line.
The shunt reactor is usually used to compensate capacitive current to ground to solve voltage rising at the receiving end of transmission lines, but if the shunt reactor is of fixed capacity, it will be removed from the compensation system once inductive current is over desired capacitive current to ground. As usual, the operation of shunt reactor connected in parallel to transmission line has a very high demand for switch, but until now, it is still very difficult to solve the over-voltage surge caused by reclosing switch.
However, our MCR type SVC can solve the above problems; it can regulate reactive power of transmission line dynamically and fast. The TCR type SVC can not be directly installed in transmission lines with voltage over 35KV, but the MCR type SVC can be installed in extra-high voltage and ultra-high voltage transmission lines directly, and it needs no action of switching. So the MCR type SVC is able to improve transmission and distribution performance of the power system remarkably. It should be installed at one or several proper points in the power grid so as to maintain a balanced voltage under different conditions and achieve the following purposes
a. Stabilize voltage of a weak system
b. Reduce transmission losses
c. Enhance transmission capability and make existing power grid more efficient
d. Improve transient stability
e. Increase the damping under small interfering
f. Enhance voltage control and stability
g. Restrain the power oscillation and the sub-synchronous resonance
3. Wind Power Plant
The output power of generator fluctuates frequently because of variable wind power. At present, the popular asynchronous wind generator (including Doubly-Fed Type) needs to absorb parts of inductive reactive power to build magnetic fields. The paralleled capacitor banks can realize compensation, but the stepped switching capacitor banks can not meet fast and dynamic reactive power compensation demand due to variable wind power. Sometimes, if the capacitor banks can not meet reactive power compensation in time, the wind generator will absorb reactive power from the upper power grid, which will result in low power factor of upper power grid and then cause voltage fluctuation. Therefore, the state grid puts forward the "Regulations on State Grid Corporation Wind Farm Grid Access Technology (Amendment)" based on voltage fluctuation, flicker, frequency deviation, harmonics and lack of reactive power:
a. No matter what kind of operating mode the wind power plant is in, it must ensure that the reactive power has essential adjustment capacity. The capacity must be the reactive power capacity determined under the rated power factor of 0.98 (lead to lag). The reactive power of wind power plant can realize dynamic and continual adjustment, and ensure adequate reactive power capacity to adjust the voltage at the point of interconnection of wind power plant to normal level.
b. For wind power base with power over 1000MW, the adjustment capacity of reactive power at single wind power plant must be the reactive power generated under the rated power factor of 0.97 (lead to lag).
c. For wind power plant connected into public power grid through booster station, the configured capacitive reactive power can compensate reactive power loss on output transmission line under full load, and the configured inductive reactive power can compensate charging reactive power on output transmission line under no load.
d. Under the premise of satisfying the above requirements, the actual reactive power capacity range of the wind power plant can be determined through research on connecting wind power plant to public power grid.
The static VAR compensator of MCR type is a good choice for the wind power plant.
4. Secondary Substation (66kV to 110 kV)
In the regional power grid, the stepped switching capacitor bank is usually used to compensate the system reactive power and increase the power factor. But it can only provide capacitive reactive power and it is unable to realize rapid and accurate adjustment according to the load variation. As a result, it sometimes provides much more reactive power than the actual desired amount, thus raising the busbar voltage, endangering electrical equipment, and reducing system stability.
Since the TCR type SVC can not be directly installed in subtransmission lines with voltage over 35KV, our MCR type SVC is a more suitable solution subtransmission. Our product is able to compensate capacitive and inductive reactive power rapidly and accurately. It solves the problems of reactive power backfeed effectively. In addition, when a new SVC system is to be installed, the existing fixed capacitor banks can be fully utilized, thus achieving the best result with the least investment. The MCR type SVC is the most effective way to improve the power quality of the local power grid. The detailed benefits are as below:
a. Reduce the reactive power exchanging with system and improve system stability
b. Rapidly and continuously compensate reactive power, increase power factor and improve power quality
c. Reduce the power losses of distribution system
d. Used in combination of stepped switching capacitor banks to reduce the damage caused by frequent switching of capacitor banks.