Operation of parallel diesel generator set

one. What are the conditions for generator sets to operate side by side? The entire process of putting

generator sets into parallel operation is called parallelism. Run one generator set first and send the voltage to the busbar. After the other generator set is started, it is parallel to the previous generator set. At the moment of closing, the generator set should not experience harmful impact current and the shaft should not be hit suddenly. After closing, the rotor should be pulled into synchronization quickly. (i.e. the rotor speed is equal to the rated speed) Therefore, the parallel arrangement of generator sets must meet the following conditions:
1. The effective value of the generator set voltage and the waveform must be the same.
2. The phases of the voltage of the two generators are the same.
3. The frequency of the two generator sets is the same.
4. The phase sequence of the two generator sets is the same.

2. What is the quasi-simultaneous parallel arrangement method of generator sets? How to make the same period parallel?

Quasi-simultaneous period is the accurate cycle. When performing parallel operation using the quasi-simultaneous method, the voltage of the generator set must be the same, the frequency is the same and the phase is the same. This can be monitored by two voltmeters, two frequency meters, the simultaneous table and the non-simultaneous indicator light installed on the simultaneous disk. The parallel operation steps are as follows:
close the load switch of one of the generator sets and send the voltage to the busbar, while the other unit is in a standby state.
At the beginning of the same period, adjust the speed of the generator set to be concurrent so that it is equal to or close to the synchronous speed (the difference between the frequency of another unit is within half a cycle), adjust the voltage of the generator set to be concurrent so that it is close to the voltage of another generator set. When the frequency and voltage are close to each other, the rotation speed of the table of the same period is slower and slower, and the indicator light of the table is sometimes light and darker. When the phase of the unit is the same as the other unit, the pointer of the table of the table is indicative of the direction of the In the middle position above, the lights of the same period are dim. When the phase difference between the waiting unit and the other unit is large, the same period table points to the downward center position. At this time, the lights of the same period are most lit. When the pointer of the same period table rotates in a clockwise direction, this means that the frequency of the generator to be concurrent is higher than that of the other unit, and the speed of the generator to be concurrent should be reduced. On the contrary, when the pointer of the same period table rotates in a counterclockwise direction, the speed of the generator to be concurrent should be increased. When the pointer of the concurrent table rotates slowly clockwise and the pointer approaches the same period point, the circuit breaker of the waiting unit will be closed immediately to make the two generator sets parallel. After parallel, remove the simultaneous table switch and related simultaneous switches.

3. What should we pay attention to when performing quasi-simultaneous parallelism of generator sets?

Quasi-simultaneous parallelism is manual operation, and whether the operation is smooth has a lot to do with the experience of the operator. In order to prevent parallelism in different periods, the following three situations are not allowed to close.
1. When the pointer of the same period table jumps, it is not allowed to close, because there may be cassette inside the same period table, which cannot reflect the correct parallel conditions.
2. When the simultaneous table rotates too fast, it means that the frequency difference between the generator set to be concurrent and the other generator set is too large. Since the closing time of the circuit breaker is difficult to grasp, the circuit breaker often does not close at the same time point, so the closing time is not allowed to be closed at this time.
3. If the pointer of the same period table stops at the same period point, the switch is not allowed to close when it is stopped. This is because if the frequency of one of the generator sets suddenly changes during the closing process of the circuit breaker, it is possible that the circuit breaker will be closed at an abnormal point.

4. How to adjust the negative power phenomenon of parallel units?

When two generator sets are no load parallel, a problem of frequency difference and voltage difference will occur between the two units. In addition, on the monitoring instruments of the two units (ammeter, power meter, power factor meter) the actual reverse work situation is reflected. One is the reverse work caused by inconsistent speed (frequency), and the other is the reverse work caused by varying voltages. The adjustment is as follows:
1. Adjustment of reverse power phenomenon caused by frequency:
If the frequencies of the two units are not equal and the phase difference is large, the current of the unit with high speed shows a positive value, and the power meter indicates positive power. Otherwise, the current indicates a negative value and the power indicates a negative value. At this time, adjust the speed (frequency) of one of the units, adjust the power meter instructions according to the power meter instructions, and adjust the power meter instructions to zero. Make the power indication of both units zero, so that the speed (frequency) of the two units is basically the same. However, when the ammeter still has an indication, this is the reverse work phenomenon caused by the voltage difference.
2. Adjustment of reverse power phenomenon caused by voltage difference:
When the power meter indications of both units are zero and the ammeter still has a current indication (i.e., one inverse and one positive indication), the voltage adjustment knob of one generator set can be adjusted. When adjusting, it depends on the indication of the ammeter and power factor. After the ammeter is not indicated, the power factor can be adjusted to 0.5, and the ammeter can be adjusted to a hysteresis of 0.8, which is an ideal state according to the power factor indicator.

5. Generator protection circuit

1. The phenomenon of reverse power
and reverse power is caused by different speed (frequency) and voltage of the generator set, that is, one generator set has positive power, while the other unit has negative power. In other words, the unit with negative power becomes a load at this time (the unit has a low frequency and inconsistent rotational speed). When the voltage is different, a unit with a high voltage provides a reactive current and reactive voltage to a unit with a low voltage (the positive indication of the ammeter of this unit), which is equivalent to adding a camera set to this power supply system. A unit with low voltage becomes a large load at this time, and receives a large reactive current to maintain the voltage balance between the two units (the ammeter inverse indication of this unit). During monitoring, the voltage of one unit is increased, or the voltage of another unit is high or low, causing a reverse power current to be produced by one unit, and its operating current is about 20%. The reverse relay operates, trips, and alarms, but does not stop.
2. Overcurrent:
The current generator set has a fixed rated power, and its overload capacity is very low, basically around 5% of the rated power. The allowable loading time is 15 to 30 minutes, and try not to exceed 60 minutes. After this time, the generator set will heat up, wire insulation will be reduced, which will reduce the service life. Therefore, when setting the overcurrent protection, the overcurrent protection can be set to 110% of the rated current. During load test, the current is brought to 110% of the rated current and the overcurrent relay operates. Trip, alarm, no shutdown.
3. Overvoltage:
When the generator set is used side by side, the power supply system oscillates. Once the oscillation system voltage increases, it is easy to cause insulation breakdown of the power consumption equipment and the power supply equipment, causing the power supply equipment to be paralyzed together with the power consumption equipment. The generator sets used side by side are all equipped with overvoltage protection, and the setting value is preferably 105% of the rated voltage. Short-circuit the overvoltage relay, trip and shut down, alarm operation.

(VI) The switch-
closing circuits are connected to the control circuits that are parallel to the mobile phone and are automatically parallel to each other.
1. Manual closing and closing: Each unit can be used as the first machine or waiting to be divided and closed. When manually combining the vehicle or supplying power, use manual closing and closing.
2. Automatic closing and closing: Each unit can be selected as a unit waiting for concurrent, or the first unit; after the first unit is started, the closing circuit will automatically close, and will automatically enter and exit the same period. After the same period, the waiting unit will be automatically closed and run in parallel.
3. Whether it is manual closing or automatic closing, once the unit experiences reverse power, after the low oil pressure, high water temperature, high water temperature, high oil temperature, and overvoltage, all of them will be automatically opened and decoupled from the load.

(7) Contemporary circuit

1. When the first machine is closed, the power supply is sent to the busbar. At this time, the busbar detects the same period loop and the same period loop that is waiting to be parallel. After receiving the signal, it automatically closes the same period detection relay. The bus voltage and the voltage of the standby machine are sent to the control module during the same period. The module automatically detects and ranks the voltage and speed of the parallel unit. If the speeds vary, the module will automatically adjust the speed of the machine to be paralleled to achieve the parallel conditions. After finding the same period point, the module of the same period issues a closing command. After the unit receives the command, the two units operate side by side.
2. After the unit is parallel, the loop of the same period will automatically exit the working state, but the automatic switching switch of the same period must be artificially exited to prevent the unit waiting for the unit to receive a parallel signal when de-ordering after incoming calls, and automatically put the unit in the same period into parallel, so that the unit will be parallel again.

(8) Load allocation

1. When running stand-alone, the load distributor is not put into operation.
2. After the unit is parallel, the load distributor of each unit is put into operation at the same time, and each unit adjusts its own speed to equally distribute the power of the two units. The working principle is to automatically adjust the speed of the unit D based on the output power of the unit (i.e. the magnitude of the current) to make its load balance.

(9) Voltage adjustment circuit:

1. Before the units are parallel, the voltages of the two units must be adjusted to the same value.
2. After no load parallel, adjust the voltage knob and deal with the reverse work phenomenon so that its power factor is about 0.8 lag.
3. After the parallel unit is loaded, the voltage adjustment knob can be manually adjusted according to the load condition so that its power factor is in position, and there is no need to adjust it in the future.

(10) Speed ​​adjustment circuit:

1. Before parallel, the speed (frequency) of the two units must be adjusted consistently.
2. When parallel, the speed of the first machine or unit waiting to be parallel can be adjusted according to the rotation speed of the same period table, so that the rotation direction of the same period table can be rotated clockwise or counterclockwise. The slower the speed, the better, but the pointer of the same period table must be rotated to be parallel.
3. After paralleling, observe whether the current and power of the two units are balanced. If the difference is too large, adjust the speed knob to adjust the power of the two units to the same.

(11) Instrument detection circuit:

1. Before operation, various related instruments must be adjusted to zero, but the power factor meter and frequency meter are not at zero.
2. During operation, observe the operating status of various instruments and whether they comply with the regulations (whether there is a phenomenon of reverse wiring).
3. Current and voltage should be checked with the relevant instrument to see if the indicator value is normal.

(12) Starting circuit:

1. Before operation, check whether the startup circuit is normal.
2. Whether the relevant components can work normally after startup.
3. Is the combination of the starter and the host normal and can exit?

(13) Shutdown circuit:

1. Whether the shutdown solenoid and solenoid valve are operated reliably.
2. Whether to automatically shut down when the unit fails.
3. Is the manual shutdown circuit perfect?
4. Just trip, whether the machine is shut down, etc.