In modern energy construction, renewable energy sources and cables are becoming increasingly common. In order to prevent the circuit system from being negatively affected by irregular active power or reactive power, shunt reactors came into being. Shunt reactors play a vital role in balancing the voltage in the circuit system.
This post primarily explains the fundamental principles and application fields of shunt reactors. The knowledge may provide solutions for your daily applications. Start your journey now!
LTEC Shunt Reactors
1. What Is Shunt Reactor?
2. Why You Need Shunt Reactor?
3. What Are The Applications Of Shunt Reactors?
4. What Are The Construction Of Shunt Reactor?
5. What Are The Characteristics Of Shunt Reactor?
6. What Is The Working Principle Of Shunt Reactor?
7. What Are The Types Of Shunt Reactor?
8. What Is The Shunt Reactor Circuit?
9. What Are The Differences Between Shunt Reactors And Power Transformers?
10. What Are The Differences Between Shunt Reactor And Shunt Capacitor?
11. What Are The Measurements Of Losses In Shunt Reactor?
12. Why Do Shunt Reactors Need To Be Switched?
13. What Are The Considerations In Selecting A Reactor Switching Device?
What Is Shunt Reactor-sourced: teknik
A shunt reactor is an important electrical device in circuit equipment. It is mainly used in high-voltage transmission systems to stabilize voltage under different loads. The main function and structure of this electrical device are the same as those of power transformers. However, unlike power transformers, shunt reactors have only one winding per phase. In long-distance high-voltage transmission lines, it can absorb or compensate for reactive power in the cable, thereby improving the application efficiency of the overall power and energy system.
Shunt reactors are the most economical way to connect long-distance high-voltage transmission lines and cable systems. Its main advantages include:
Improving the energy efficiency of long-distance transmission
Improving the energy efficiency of long-distance transmission-sourced: wikimedia
In long-distance transmission lines, reactive power is generated due to the capacitive effect between the line and the ground. Reactive power hurts the circuit. In order to reduce or balance such energy losses, shunt reactors can absorb or compensate for these reactive powers, thereby improving the power energy efficiency of the system.
Balanced voltage stability
Balanced voltage stability-sourced: mdpi
In low-load circuit systems, the voltage on the transmission line will increase, and shunt reactors can reduce this voltage increase and keep the voltage of the entire transmission line within the required range to improve the voltage stability of the entire system.
Adjust with load changes
Adjust with load changes-sourced: linquip
Since the entire transmission system is affected by daily or seasonal load changes, shunt reactors can continuously compensate, eliminate, or adjust according to the user's load usage requirements over time. This adjustment can make the entire system operate more optimally. It can also be used in conjunction with other systems, such as static VAR compensators or high-voltage DC transmission lines.
Shunt reactors have a wide range of uses, including:
Transmission lines or cables
Transmission lines or cables-sourced: wired
It can be used in various compensation transmission lines and cables, and can absorb or compensate for reactive power in transmission lines or cables to improve energy system efficiency.
High-voltage or ultra-high-voltage systems
High-voltage or ultra-high-voltage systems-sourced: zmscable
Shunt reactors can be used in different systems, such as high-voltage or ultra-high-voltage systems. It can optimize the existing network state or network voltage in dynamic conditions and enhance network stability. When the entire line is running at low load or no load, it can continuously adjust the voltage to improve the quality of electric energy and the stability of voltage.
What Are The Construction Of Shunt Reactor-sourced: studyelectrical
The shunt reactor mainly adopts a three-winding structure. The three windings are star-connected, and the neutral point is accessible. Its neutral point can be connected to the grounding system of the device through the third winding of the power transformer or directly. The built-in protection device of this system is the same as the design structure used in the power transformer.
Because the shunt reactor mainly includes two types, oil-immersed reactor with oil storage cabinet and dry reactor, the auxiliary equipment used by it mainly includes oil pressure relief valve and air respirator. Its protection device and accessories are the same as those of the power transformer, especially in the oil-immersed reactor, the oil pressure in its pressure relief valve and vent valve is the same.
The main characteristics of shunt reactors include impedance, thermal rating, and sound level.
Impedance
To avoid harmonic currents under system overvoltage conditions, the constant impedance of the shunt reactor is 1.5 times the rated voltage, and this impedance must be accurately balanced between the three-phase reactors.
Thermal rating
Thermal rating-sourced: 686
Since the shunt reactor operates at 420 kV, its temperature will rise. Therefore, in order to ensure that the reactor can operate continuously at the rated voltage, the hot spot temperature of any of its components should not exceed 1500℃.
Vibration and audio sound level
Vibration and audio sound level-sourced: nti-audio
To ensure that the noise and vibration of the shunt reactor during continuous operation can be minimized, it is designed to ensure that the natural vibration period of the reactor's housing shield or yoke does not vibrate when excited at the rated frequency. And its audio volume should not exceed the normal acceptance level of the same mVA and rated voltage.
The main working principle of the shunt reactor is:
What Is The Working Principle Of Shunt Reactor-sourced: researchgate
- By absorbing reactive power in the transmission line, the efficiency of the energy system is improved.
- By compensating for reactive power in high-voltage transmission lines and cable systems, the stability of the power system is improved.
- By connecting the shunt reactor directly to the power line or the third winding of the transformer, it can withstand the highest continuous working voltage.
- The temperature of any component in the shunt reactor cannot exceed 150℃, and the voltage is higher than 5% of the rated voltage.
- Since the shunt reactor may produce core losses when operating under normal conditions, these losses must be reduced during use.
Shunt reactors mainly include oil-immersed and dry types.
Dry Shunt Reactor
Dry Type Shunt Reactor-sourced: googleusercontent
Dry shunt reactors are generally installed on the third winding of the transformer and connected to the compensated transmission line. Its limiting voltage is 34.5kV. The center of this reactor is an air-core type. Shunt reactors are mainly suitable for use in indoor or outdoor exposed environments. Compared with oil-immersed shunt reactors, dry shunt reactors are light in weight, low in cost, low in loss, and require less maintenance. The disadvantage is that the rated voltage is limited, and the external magnetic field strength is high. Therefore, there is no iron core at startup, so there is no excitation surge current, etc.
Oil-immersed Shunt Reactor
Oil-immersed Shunt Reactor-sourced: peoplepower
Oil-immersed shunt reactors mainly include coreless type and air-gap iron core type. Both structures have low-frequency, long constant current when the power is off. And the excitation surge current of the air-gap iron core type is more intense than that of the coreless type. The appearance of this reactor is very similar to that of an ordinary power transformer. Its design is all with magnetic shielding. And its magnetic shield surrounds the coil, which can keep the magnetic flux within the inductor tank.
What Is The Shunt Reactor Circuit-sourced: electricaltechnology
The line of shunt reactor mainly refers to the shunt reactor connected at both ends of the ultra-high voltage line. Such a connection design is mainly to prevent the line voltage from exceeding the design value when they are started from one end. Usually, since customers cannot determine which end is powered on or off first, these shunt reactors are connected at both ends of the ultra-high voltage line. Such a connection design is to enhance the regulation of reactive power utilization, and the shunt reactor is also variable.
Although the structure of the shunt reactor and power transformer is the same, there are still some differences in use and function, mainly including:
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Shunt Reactors
Shunt Reactors-sourced: LTEC |
Power Transformers
Power Transformers-sourced: circuitdigest |
|
| Winding | A shunt reactor has only a single winding. | A power transformer has three windings. |
| Function | Shunt reactor is mainly used to consume or absorb reactive power in the circuit system, so as to improve the efficiency of the whole system. | Power transformer is mainly used for voltage change and voltage step-up or step-down in the whole transmission system. |
| Side ampere-turns | Since the shunt reactor has no other windings, its side ampere-turns (AT) are equal to the secondary side ampere-turns (AT). | The primary side ampere-turns (AT) of a power transformer are equal to the excitation ampere-turns (AT); |
| Structural design | In order to prevent hysteresis loss, the shunt reactor is generally designed as a structure without an air core or an iron core. | A power transformer is generally an iron-core structure. |
| Rated capacity | The rated capacity of the shunt reactor is MVAr. | The rated capacity of the power transformer is kVA. |
| Application range | Shunt reactors are mainly used in high-voltage systems and cable networks to improve line system efficiency. | Power transformers are used for voltage conversion and to stabilize system voltage. |
Shunt reactor and shunt capacitor are two different electrical devices; their main differences include:
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Shunt Reactor
Shunt Reactor-sourced: LTEC |
Power Capacitor
Shunt Capacitor-sourced: weishielectronics |
|
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Structure |
A shunt reactor is one or more capacitor units used to improve the power factor. |
A shunt capacitor is specially used to connect to the transmission line to stabilize the voltage when the load changes. |
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Function |
Provide reactive power to the system and improve the power factor. |
Absorb reactive power in the system and stabilize the voltage. |
|
Voltage conditions |
Under light load conditions, it will cause the voltage to increase. |
Causes a slight voltage drop. |
|
Connection |
Directly connected to the power line. |
Directly connected to the transmission line or the tertiary winding of a three-phase transformer. |
|
Others |
It may amplify harmonics in the system. |
Eliminate harmonics in the system. |
What Are The Measurement Of Losses In Shunt Reactor-sourced: ergunelektrik
- You generally need to measure the losses of the shunt reactor at rated voltage and frequency. If the losses are measured under ultra-high voltage, the displayed results will be complicated to analyze. Therefore, you need to measure the losses under any conditions below the reactor system voltage.
- Multiplying the measured losses by the square of the ratio of the rated current to the reactor current gives the transmission system losses at rated voltage.
- When the power factor of the shunt reactor is low, the traditional power measurement loss results are unreliable, and higher measurement technology is required to obtain higher loss accuracy. And you need to measure different windings at normal temperature.
Why Do Shunt Reactors Need To Be Switched-sourced: electrical-engineering-portal
In different application scenarios, in order to meet the different power needs of customers, shunt reactors need to be switched. The main principle of switching is that when the load in the transmission line increases, the voltage drops, and you need to turn off the reactor. When the load decreases, the voltage rises again, and you need to turn on the reactor. For systems with frequent load fluctuations, your reactor switching may also be very frequent.
Because the equipment is frequently switched, it will cause stress on the insulation and the inter-turn insulation of the reactor, which may cause premature failure of the equipment or damage to nearby equipment. Therefore, when designing the application, you should take into account the small inductive current generated when the reactor needs to be switched frequently.
When choosing the switchgear for shunt reactors, you need to consider the following points:
Switching frequency
Switching frequency-sourced: southernstatesllc
The switching device of the shunt reactor depends on the different applications and the frequency of use. Most reactors are generally divided into three categories: fixed reactors, reactors with infrequent switching, and reactors with frequent switching.
- Fixed reactors
Fixed reactors-sourced: sciencedirect
Fixed reactors are mainly used in some ultra-high voltage and long-distance transmission lines. Its load is always much lower than the surge impedance load. Therefore, the shunt reactor is always in operation. This continuous operation does not cause high loads or require regular shutdown.
- Infrequently switched reactors
Infrequently switched reactors-sourced: southernstatesllc
Infrequently switched reactors are mostly in the on or off state. This type of reactor is mainly opened in specific emergency situations.
- Frequently switched reactors
Frequently switched reactors refer to reactors that need to be closed and opened more than 100 times a year. This type of reactor is mainly used in various renewable energy sources, such as wind and solar transmission lines.
Breaking small inductive currents
If the current consumption of the shunt reactor is usually 300A or less, then such a small inductive current is difficult to break at first, and when the current is extinguished, the voltage of the shunt reactor will oscillate towards zero at the natural frequency of the reactor.
Shunt reactors can absorb and balance reactive power in high-voltage transmission lines, thereby improving the power and efficiency of the system. If you want to know more about the applications and advantages of shunt reactors, please feel free to contact us now!
