Why is the generator frequency higher than the grid frequency when connected to the grid

Because when connected to the grid, if the generator voltage and frequency are not higher than the system, the generator will be used as a load by the grid, but consume energy.

1. Just like when the mobile phone is charging, if the charger voltage used is too low, it will lead to a long charging time or a situation where the charging time is not available, and in some cases, the more you charge, you will find that the mobile phone consumes more power than usual, because the charger has become a load.

2. Theoretically, it is best to have the same voltage frequency between the generator and the power grid, but in practice it is difficult to do. Therefore, in actual operation, it is better to use the generator slightly higher than the grid, so that the power can be sent at the moment of grid connection, rather than absorbing power from the grid.

In layman's terms, the purpose of a generator connected to the grid is to send electrical energy to the grid. Only the prime mover of the generator (internal combustion engine, steam turbine or water turbine, etc., the following internal combustion engine as an example) can send energy, and this force is achieved by increasing the throttle of the internal combustion engine.

When the generator is connected to the grid, if the frequency of the generator and the grid is exactly equal, in fact, the internal combustion engine only provides the active power to maintain rotation to overcome the mechanical resistance, and does not send out electricity; Conversely, if the frequency of the generator is lower than the frequency of the grid, the power from the grid is backflowed, the so-called "reverse power". Only when the generator frequency is higher than the grid frequency can the power be pushed out.

Therefore, after the generator is connected to the grid, the operator will raise the throttle of the internal combustion engine and observe the output power meter until the expected value is reached. Although the textbook will say that the frequency will be synchronized after grid connection, in fact, the frequency of the generator has a tendency to "top" the frequency of the grid.

It's like two people carrying something with a flat pole, both shoulders are the same high, everyone has the same effort, and no one will take advantage. But if one of them stands on tiptoe, then that person will contribute more, and the other will share the lightness.

If it is not consistent, there is a frequency difference, which will cause an impulse voltage to be generated. In the cylinder of the diesel engine, the clean air filtered by the Nian air filter is fully mixed with the high-pressure atomized diesel injected by the fuel injector.

Under the squeeze of the piston upward, the volume is reduced, and the temperature rises rapidly, reaching the ignition point of diesel. The diesel fuel is ignited, the gas mixture burns violently, and the volume expands rapidly, pushing the piston downward, which is called 'work'.

Why is the voltage at the end of the generator connected to the grid at the same time lower than the system voltage, 1. For the generator, it is generally a delayed phase operation, and its load is generally a resistive and inductive load. 2. When the generator is boosted and connected to the grid, the stator winding flows through the current, which is the inductive current, and the inductive current reacts relatively well in the armature inside the generator, which weakens the rotor magnetic field, so that the terminal voltage drops due to the coarse slag. 3. When only the active current flows, it also has the same effect, but the impact is relatively small.

4. This is because the stator winding generates a magnetic field when the current flows, half of this magnetic field plays a role in magnetizing the rotor magnetic field, and the other half plays a demagnetizing role, due to the saturation of the rotor magnetic field, the magnetization side is always weaker than the demagnetization side. 5. Therefore, the magnetic field will weaken, resulting in a decrease in the terminal voltage. , I hope that the stool rush can help you.

Why is the voltage at the end of the generator lower than the system voltage after the generator is connected to the grid at the same time Hello, dear, 1For generators, it is generally a delay-phase operation, and its load is generally resistive and inductive. 2.

When the generator is boosted and connected to the grid, the stator winding flows through the current, which is the inductive current, and the inductive current reacts more strongly in the armature inside the generator, which weakens the rotor magnetic field, thereby causing the terminal voltage to drop. 3.When only the active current is flowing, it has the same effect, but the effect is smaller.

4.This is because the stator winding spike produces a magnetic field when the current is crossed, half of this magnetic field plays a role in the magnetic field of the rotor, and the other half plays a role in demagnetization, due to the saturation of the rotor magnetic field, the side of the magnet is always weaker than the side of demagnetization. I hope I can help you, if my answer is helpful to you, please give a thumbs up (comment in the lower left corner), look forward to your like, your efforts are very important to me, and your support is also the motivation for my progress.

Finally, I wish you good health and a good mood!

The generator is an inductive element, and when you undo the voltage at both ends of the motor winding, it instantaneously generates a large voltage.

The frequency must be equal, and the electrical energy can only be sent out if the voltage is a little less, or it can be sent out if the phase is slightly ahead.

The upper end of the switch is connected to the electricity of the power grid, and the lower end of the switch is the electricity of the generator.

There are self-synchronous method and quasi-synchronous method for generator grid connection.

The parallel method of self-synchronization is to put a generator that is not excited and whose speed is close to the synchronous speed into the system and add excitation immediately (or after a certain period of time). In this way, the generator is automatically pulled in and synchronized with the grid in a very short time.

The quasi-synchronous method is to adjust the excitation current and speed of the generator, and integrate the generator into the grid when the generator and the grid are in the same phase sequence, equal frequency, equal voltage, and same phase.

Four conditions for grid connection of generators by quasi-synchronous method:

1.The frequency of the generator is the same as the frequency of the system.

2.The generator outlet voltage is the same as the system voltage, and its maximum error should be within 5%.

3.The generator phase sequence is the same as the system phase sequence.

4.The generator voltage phase is the same as the system voltage phase.

The specific operation steps of the quasi-synchronous method of hydrogenerator parallel: first open the water gate, let the speed be close to the rated speed, and then close the excitation switch, adjust the excitation current and speed of the generator, so that the frequency and voltage of the generator and the power grid are close, and then close the synchronization meter, fine-tune the excitation current and speed, so that the synchronization meter speed is getting slower and slower, when the phase is less than 15 degrees, and slowly close to 0 degrees, the switch will be close and running when it is close to 0 degrees or 0 degrees. The closer the moment of closing, the smaller the impact on the grid and generators.

The advantage of using a synchronization meter to connect to the grid is that if the phase error is 15 degrees or more, the switch will not work.

Before connecting to the grid, it is necessary to make the phase sequence of the generator and the power grid consistent, otherwise it will short-circuit and burn the generator, causing a major accident.

1. The simplest is to use a multimeter to measure, the multimeter hits the voltage gear, one meter pen is connected to the bus A phase, and the other meter pen is connected to any phase of the generator, and any phase is measured to have no voltage, which is A1 in the same phase as the bus A; In the same way, one meter pen is connected to the bus B phase, and the other meter pen is connected to any phase of the generator, and no voltage is measured in any phase, which is B1 in the same phase as the bus B; A1 and B1 are OK, and the rest is C1.

2. You can also use a small three-phase motor, connect the motor to the bus first, and remember the steering of the motor and the three-wire marking; Then connect the motor to the generator, if the steering is consistent, it means that the phase sequence is consistent. Otherwise, it means that the phase sequence is inconsistent, and then, adjust the generator outlet line to be consistent with the bus phase sequence.

3. Light out method or light rotation method. If the voltage on the three lamps is equal and changes at the same time, the brightness and darkness of the three phase lights also change at the same time, indicating that the phase sequence of the generator is consistent with the phase sequence of the bus; If the three-phase lights turn on and off (the three phase lights turn off, when one phase light goes out, the other two phase lights have the same brightness; This means that the phase sequence of the generator is different from that of the power grid, and any two outgoing wires of the generator should be swapped, the phase sequence of the generator should be changed, and then the operation should be re-operated to ensure that the phase sequence is consistent.

Generators are not only connected to the grid.

BAI only looks at the frequency du rate, but also considers the generator voltage, ZHI phase sequence and waveform. The friend replied, "Suppose the frequency of the generator and the frequency response rate of the grid are exactly the same. The phase difference is constant, so how can it be connected to the grid? "It's because of a lack of conceptual clarity.

Usually the generator grid connection is judged by the synchronization indicator, and the simplest synchronous indication method is the light method. From the perspective of the four elements in the grid connection condition, the phase sequence and frequency are the most critical, if the phase sequence is incorrect, it can never be connected to the grid; When the phase sequence is correct, the frequency and phase difference are considered, here the frequency difference determines the number of flashes of the light method, and the phase difference determines the brightness of the light method, the lamp disposition difference is large, and the phase difference of the lamp darkness is small.

The generator frequency is exactly the same as the grid frequency, but the phase difference is large and cannot be connected to the grid. Although there is a slight deviation in the frequency at this time, the generator in operation has the characteristics of self-pacing with the power grid, and it will be at the same frequency after being connected to the grid.

Yes, you are right, that is, by fine-tuning the frequency of the generator, the purpose of phase shifting is achieved.

You look carefully at the device instructions.

As well as the source protection description, frequency, voltage are +-, that is, the instrument measures the phase and the large power grid display is consistent, in fact, there is still a slight difference, but once connected to the grid, it will be brought by the large network, the extreme situation: in the past, when the manual was completely looked at the same time, the novice grid connection error, when there is a large phase difference, the forced grid connection, will be forced to go forward or backward to the same frequency and phase, and the generator will ring.

You're naïve! Is it possible that the generator frequency and the grid frequency are exactly the same?

When the generator is connected to the grid, the frequency is not the same, but close, and the phase difference will be 0 moment. The frequency of the generator is adjusted by adjusting the speed of the steam turbine.