About the flow direction of reactive power in the power system

Hehe. Reactive power.

The flow direction can be understood by the flow direction of electrical energy, or the concept of electrical energy flow can be understood. It is from reactive power to flow from there to there. To determine the direction of reactive power, it can be simply judged from the direction of reactive current.

For example, the motor needs reactive power, and the reactive current flows from the transformer (power supply) to the motor, so the direction of the reactive power is the power supply load. Another example: phase-modulated generator, which can emit reactive power and absorb reactive power.

When the reactive current flows into the phase-modulated generator (absorbing reactive power), the direction is negative, and vice versa.

Voltage and reactive power are one of the important indicators of power quality. Excessive voltage excursion will affect the operating characteristics of the electrical equipment, and also affect the power taken by the electrical equipment, which will adversely affect the system, such as asynchronous motors. The reactive power is closely related to the system voltage level.

In order to ensure that the system voltage must have sufficient reactive power. The reactive power is transmitted from the power supply end to the load end through the line and transformer, and the voltage loss (the voltage loss of the high-voltage line and the transformer mainly depends on the reactive power passing through), and the change of the reactive power flow will also cause the change of voltage loss. The deficiency of reactive power will cause the voltage level of the system to drop, and the balance of reactive power can only be achieved at a lower voltage in the case of insufficient reactive power supply.

In order for the voltage to rise, it is necessary to increase the reactive power output of the power supply.

The voltage and current of alternating current are both synchronized. Voltage and current act on the load at the same time. is the active power.

It's like force plus displacement in mechanics to do work. Since the load is not necessarily a pure resistance. The current and voltage produce a phase difference.

The residual angle of the phase difference is the power factor. The flow direction of reactive power is not clear. is a scalar quantity.

There is only size and no direction.

The relationship between active power and voltage: when the active power emitted by the grid is equal to the active load of the user, the frequency remains the same; When it is less than the active load, the frequency decreases; When it is greater than the active load, the frequency rises. Therefore, changing the active power output of the generator can adjust the grid frequency.

Under normal circumstances, the total active power emitted by the generator in the power system and the total active power consumed by the load are balanced, and the system frequency can be maintained at the rated value. The change in the frequency of the system is a direct reflection of the balance of active power. If the power is greater than the use, the system frequency increases.

Control Data:

The establishment of a large-scale power system with a reasonable structure is not only convenient for the centralized management, unified dispatching and distribution of electric energy production and consumption, reducing the capacity of the power plant, saving the investment in power facilities, but also conducive to the rational development and utilization of regional energy resources, and meeting the growing electricity needs of the regional national economy to a greater extent. The construction of power system is often an important part of national and regional national economic development planning.

The emergence of the power system, the use of efficient, pollution-free, easy-to-use, easy-to-control electric energy has been widely used, which has promoted changes in all fields of social production, created the era of electric power, and the second technological revolution has occurred. The size and technology of the power system has become one of the indicators of a country's economic development level.

The active power and reactive power points may not be at the same point; If the original network is not disconnected at the same point with a lower voltage, the reactive power point is usually selected. Power equinox: A node in a power grid where power flows from two directions. The active power and reactive power points may not be at the same point; If the lead chain is not at the same point, the lower voltage point is selected to untie the original network, and the reactive power point is usually selected to disassemble the network.

After the preliminary power flow distribution is calculated, you can see that the power on both sides of a node in the network flows to the node, which is the power node. Extended data The hazards of reactive power: reactive power has a certain adverse effect on the power supply and use, which is mainly manifested in:

1. Reduce the output of the active power of the generator 2, reduce the power supply capacity of the transmission and transformation equipment 3, and increase the line voltage loss and power loss. 4. Cause low power factor operation and voltage drop, so that the capacity of electrical equipment can not be fully utilized.

Conditions for transmitting active power: The voltage at the beginning and end needs to have a phase angle difference, and it needs to flow from the phase advance to the phase lag end.

Conditions for transmitting reactive power: there needs to be a voltage amplitude difference between the beginning and end of the line, which is from the high-voltage side to the low-voltage side.

Active power is the electrical power that converts electrical energy into other forms of energy (mechanical energy, light energy, thermal energy) and is known as active power. Represented by the letter P, the units are mainly watts (W), kilowatts (kW), and megawatts (MW). The instantaneous power of alternating current is not a constant value, and the average value of instantaneous power in a cycle is called active power, therefore, active power is also called average power.

Reactive power is in an AC circuit with reactance, where the electric or magnetic field absorbs energy from the power supply for part of a cycle and releases energy for another part of the cycle, and the average power is zero throughout the cycle, but the energy is constantly exchanged between the power supply and the reactive element. In a single-phase AC circuit, its value is equal to the product of the rms voltage, the rms current, and the sine of the phase angle between the voltage and the current.

1.First of all, there should be a power system line to form a loop;

2.A power supply (generator) with a stable voltage and frequency

Your question is literally more difficult to explain. Can you narrow down the problem a bit?

The transmission of active power requires that the voltage at the beginning and end has a phase angle difference, and it flows from the phase lead to the phase lag end.

If the transmission is reactive, I personally feel that there needs to be a voltage amplitude difference between the beginning and end of the line, which is from the high-voltage side to the low-voltage side.

1.First of all, there should be a power system line to form a loop;

2.A power supply (generator) with a stable voltage and frequency

1. The impedance of the network components of the power system is mainly inductive, and the phase difference of the output voltage of each unit in the parallel system mainly causes the difference of active power, so that the active circulation is formed between the parallel units.

2. The amplitude difference of the output voltage mainly leads to the difference of reactive power, so that the reactive current is formed between the parallel units. Keyouyun approximates that the difference in active power is proportional to the phase difference, and the difference in reactive power is proportional to the difference in amplitude.

3. Inductive equipment not only needs to absorb active power to the power system during operation, but also absorbs reactive power at the same time. When the line transmits a fixed amount of active power, if the more reactive power is transmitted, the greater the voltage loss of the line, that is, the lower the voltage sent to the user end, which leads to a value difference between the voltage of the transmitting end and the receiving end.

The power system is a production and consumption system composed of power plants, transmission and transformation lines, power supply and distribution stations and electricity consumption.

Its function is to convert the primary energy in nature into electrical energy through power generation power devices, and then transfer the electric energy to various users through transmission, transformation and distribution. In order to achieve this function, the electric spring beam force system also has corresponding information and control systems in all links and different levels, which measure, regulate, control, protect, communicate and dispatch the production process of electric energy, so as to ensure that users obtain safe and high-quality electric energy.

The larger the excitation current, the stronger the rotor magnetic field, and the higher the induced electromotive force in the stator coil at the same speed; At no load, the extreme voltage depends on the magnitude of the rotor's magnetic field; When a load is applied, the magnetic field generated by the load current in the stator coil (armature reaction magnetic field) and the rotor magnetic field form a resultant magnetic field, and the terminal voltage depends on the magnitude of the resultant magnetic field.

Due to the difference in the magnitude and nature of the load current, the armature reactive magnetic field has the effect of strengthening (when entering the phase) or weakening (when the phase is delayed) on the rotor magnetic field, and the current in the stator current that produces the enhanced or weakened magnetic field is the reactive current, and the current multiplied by the voltage is the reactive power.

If the reactive power is balanced, then the terminal voltage remains unchanged, if the load changes, the armature reaction magnetic field changes cause the change of the synthetic magnetic field, the terminal voltage will fluctuate, then we need to adjust the excitation current to adjust the size of the rotor magnetic field to keep the synthetic magnetic field unchanged, so as to maintain the terminal voltage unchanged.

The excitation current is the current flowing in the rotor of the synchronous motor (with this current, the rotor is equivalent to an electromagnet, with n pole and S pole), and during normal operation, this current is generated by the DC voltage applied to the rotor externally. This DC voltage is supplied by DC motors, and most of them are supplied by thyristors after rectification.

Summary. Pro, the method for determining the direction of the power flow of reactive power flow and active power of power system; In the power system, the power flow direction of reactive power is related to the phase angle difference of the voltage, while the power flow direction of the active power is related to the amplitude of the voltage. In the case of reactive power, since it is related to the phase angle difference of the voltage, its flow direction is related to the phase angle difference of the current.

Normally, a power supply, such as a generator, provides reactive power, so if the load consumes reactive power, the direction of the power flow will flow from the power supply to the load; If the load generates reactive power, the direction of power flow will flow from the load to the power supply.

Pro, the method for determining the direction of the power flow of reactive power flow and active power of power system; In the power system, the power flow direction of reactive power is related to the phase angle difference of the voltage, while the power flow direction of the active power is related to the amplitude of the voltage. For reactive power, since it is related to the voltage phase angle difference, its flow direction is related to the phase angle difference of the current. In general, the power supply (such as a generator) provides reactive power, so if the buried dust of the bending load consumes reactive power, the direction of the power flow will flow from the power supply to the load; If the load generates reactive power, the direction of power flow will flow from the load to the power supply.

I'm sorry I don't understand, but can you elaborate on that?

Pro, the method for determining the direction of the power flow of reactive power flow and active power of power system; In the power system, the power flow direction of reactive power is related to the phase angle difference of the voltage, while the power flow direction of the active power is related to the amplitude of the voltage. For reactive power, since it is related to the voltage phase angle difference, its flow direction is related to the phase angle difference of the current. In general, the power supply (such as a generator) provides reactive power, so if the buried dust of the bending load consumes reactive power, the direction of the power flow will flow from the power supply to the load; If the load generates reactive power, the direction of power flow will flow from the load to the power supply.

Answer]: The flow direction of active power in the power system is from the node with phase advance to the node with phase lag.