Automatic Reactive Voltage regulator
With the rapid development of national economy and the improvement of people’s living standard, people’s demand for electricity is increasing day by day. It puts forward higher request to the reliability and quality of power supply. However. Distribution network construction is seriously lagging behind, the grid is weak, facilities aging, line length, small diameter, most of the power distribution transformers are high energy consumption, network loss is increasingly prominent.
Voltage quality is one of the important indicators to measure the power quality of power system, and its quality depends on whether the power flow distribution is reasonable or not. Due to the increasing load and the power supply, the network structure of the power system not only changes the network structure of the power system, but also changes the power distribution of the system. May even cause serious problems in local areas, the situation is generally low voltage level. This is not only related to the power system to provide users with power quality issues, but also directly affect the safety and economic operation of the power grid. At the same time, it is necessary to consider the power factor and voltage of the network, because the network power factor and voltage reduction will make the electrical equipment is not fully utilized, thereby reducing the transmission capacity of the network, and cause loss increase.
- Improves system power factor
- Reduces network losses
- Avoid penalty charges from utilities for excessive consumption of reactive power
- Reduces cost and generates higher revenue for the customer
- Increases system capacity and saves cost on new installations
- Improves voltage regulation in the network
- .Increases power availability
The need for capacitors in electric power system
Rated voltage：6kV to 35kV
（30kV—230kV Power transformer substation）
Rated frequency：50Hz, 60Hz
Rated reactive power capacity：50kvar—36000kvar
Compensation taps：9 to 25 taps
Voltage regulation range：50%Un—100%Un
Regulation reactive power range：25%Qn—100%Qn
Controller system：DWK controller
The work principle of Farady regulating type capacitors is that: Connect all the capacitors to the electric network with voltage regulator ,the output reactive power will be adjust by voltage regulator, refer to the capacitor output power formula: Qc=(U/Un)²Qn.
The set of equipment is made up by following equipments:
- Load break switch
- Insolating switch
- Voltage regulator
- Intelligent controller
- Lighting arrester
- Metering CT, PT
Assuming that the nominal capacitance of the capacitor is Qn , the connected voltage regulator regulation range is 50%Un—100%Un, so refer to the formula ,voltage regulator is designed with 9 taps tap changer to change the network voltage, see figure 2 , the output reactive power in every regulator position
The traditional way of reactive power compensation is changing the quantity of capacitors to adjust output reactive power, change method is usually switch or contactor, will result in following hazards
- The conventional reactive power compensation method has a large compensation capacity and the adjustment is not flexible, it will lead to the compensation is not suitable , often appear over and not enough.
- The capacitor switching can cause over-voltage and inrush current, and it will seriously affect and reduce the service life of the switch.
- When the capacitor is switched on, as the capacitor will charged and discharged, when it need to switch on again, which affects the speed of the switching.。
According to the above problems, o company developed the FLYK type reactive power compensation device, has the following advantages：
1.Energy conservation: Farady voltage regulating type capacitors will change the output reactive power by regulating voltage on capacitors, so that the reactive power can be adjusted smoothly. Comparing with other method, it can ensure the capacitors in best condition, the energy saving effect is much better
2.Low cost：If the old power transformer substation need to reform, only need to add a voltage regulator between the circuit breaker and capacitors, the original circuit breakers, reactors, capacitors can be reuse, greatly reduce the cost of transformation
3.Maintance Free：When traditional circuit breaker and contactor switching, switching devices and capacitors often damaged because of the above problems, result in high maintenance costs, using Farady devices, automatic control reactive power output, there is no potential risks of other equipments, greatly reducing maintenance and staff costs in power transformer substation
Figure 3 DWK controller
- A controller can control the 1-2 power transformer, 1-2 capacitor group, through the menu settings to meet different control situation. The control panel circuit can be used in different equipment. Especially considering a series of adjustable capacitors and with a set of adjustable capacitors, to achieve the maximum performance.
- A voltage regulator is designed in accordance with the nonlinear voltage, so that the reactive power capacity of each tap is equal. According to reactive power control and not according to the power factor control, switching shocks does not appear.
- According to the line switch and the main switch automatically determine substation operation mode and automatically adjust reactive decision signal.
- Dedicated capacitor protection, while protecting both the two regulator and capacitors, it will set the protection value according to tap position of voltage regulator. Also with current delay, instantaneous trip, opening voltage, overvoltage and under voltage protection system.
- Each capacitor can be cast back at any time by pressing plate. Capacitor failure can automatically exit the fault equipment, does not affect the operation of other equipment. Automatic removal of the capacitor switch cabinet, and alarm.
- With the communication interface and the contact type pressure regulating interface, convenient and comprehensive automation.
- A variety of models to meet the different needs of the controller.
This type of devices install all electrical components in the cabinet that required, cabinet made of galvanized steel or stainless steel, the voltage is 3 5kV and below, capacitance below 4000kvar will use such structure. This type of structure is orderly, the installation and the maintenance are convenient, the occupied area is small, and the structure is suitable for the interior installation of a new power transformer substation.
This install type with a fence around the equipment enclosure , occupy an area of slightly larger, but the maintenance is very convenient, also have in indoor and outdoor for use, this kind of installing usually for old power transformer substation reforming and factory reactive power compensation.
1．When capacitor is the main compensation power, the reactive power problem is solved, the line power factor is improved, the voltage drop is reduced, the reactive power loss is reduced, and the terminal voltage level of the stable line is reduced. Suitable for urban and rural fringe areas, since the overhead line is long, result in the voltage is too low,
2．When the reactor is the main compensation reactive power, it mainly solves the problem of large and seasonal voltage difference between day and night, and the problem of voltage instability. Suitable for ultra high voltage hub substation, urban power grid, the day and night pressure difference, the night capacitive reactive surplus places to install and use. The power frequency voltage rise caused by the capacitance effect of long lines can be weakened when the overhead line is empty or light load. Such end Voltage rise is due to the high voltage overhead line no-load or light load, the line of the power grid for capacitive reactive power charging, resulting in line terminal voltage is higher than the first voltage,
3．When the capacitor and shunt reactor are combined as the main compensation of reactive power, can Synthetically solve the problem of voltage reactive power. Suitable for large power, power factor, voltage levels have higher requirements for the installation and use places.
4．The high voltage filter compensation device is used as the main compensation and harmonic control of reactive power which mainly solves the problem of excessive harmonic and low power factor. At the same time, it can also reduce the voltage drop, reduce the reactive power loss and harmonic additional loss, and stabilize the terminal voltage level. For a harmonic source, medium voltage overhead lines long, low voltage, low power factor of the installation site