Parallel Running Condition of Generator Set

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I. What are the conditions for Parallel Running of generator sets?

The whole process of putting the generator set into parallel operation is called parallel operation. Run one generator set first and send the voltage to the bus. After the other generator set is started, it should be in parallel with the previous generator set. The generator set should not have harmful impact current at the moment of closing, the shaft is not suddenly impacted. After closing, the rotor should be quickly pulled into synchronization. (That is, the rotor speed is equal to the rated speed) So the generator set must meet the following conditions:

1. The valid value and waveform of the Generator Set voltage must be the same.

2. The two generators have the same voltage phase.

3. The two generator sets have the same frequency.

4. The phase sequence of the two generators is consistent.

2. What is the quasi-same-period parallel method of the generator set? How to perform parallel operation during the same period?

A quasi-period is an accurate period. The quasi-same period method is used for parallel operation. The voltage, frequency, and phase of the generator set must be the same, this can be monitored by two voltage meters, two frequency tables, and the same period table and non-same period indicators mounted on the same period disk. The parallel operation steps are as follows:

Close the load switch of one generator set and send the voltage to the bus, while the other is in the waiting state.

Close the start of the same period, adjust the rotation speed of the waiting generator set so that it is equal to or close to the synchronous speed (the frequency of the other unit is less than half a week), and adjust the voltage of the waiting generator set, it is similar to the voltage of another generator set. When the frequency and voltage are similar, the rotation speed of the table during the same period is getting slower and slower, and the indicator lights are also on and dark during the same period; when the phase of the waiting unit is the same as that of the other unit, the pointer in the same period indicates the center position in the upward direction, and the lamp in the same period is the shortest. When the waiting unit has the largest phase difference with the other unit, during the same period, the table points to the center of the bottom, and the lamp is the brightest in the same period. When the table pointer rotates clockwise in the same period, this indicates that the frequency of the waiting generator is higher than that of the other unit, the rotation speed of the waiting generator set should be reduced. Otherwise, when the table pointer rotates counterclockwise during the same period, the rotation speed of the waiting generator set should be increased. When the table pointer rotates slowly clockwise during the same period, and the pointer approaches the same period, the circuit breaker waiting for the current unit is closed immediately, so that the two generators are tied together. After the parallel operation, the simultaneous table switch and related synchronous switches are removed.

3. What should I pay attention to during the quasi-Same Period of the generator set?

The parallel operation in the quasi-same period is a manual operation, and whether the operation is successful has a lot to do with the operator's experience. To prevent the parallel operation in different periods, no close is allowed in the following three cases.

1. When the table pointer jumps during the same period, it is not allowed to close the table because the table may be stuck in the same period, which does not reflect the correct parallel conditions.

2. when the table rotation during the same period is too fast, it indicates that the frequency of the waiting generator set is too different from that of the other generator set. Because the closing time of the circuit breaker is difficult to grasp, the circuit breaker is often closed at the same period, therefore, no closing is allowed at this time.

3. If the table pointer remains unchanged at the same period, it is not allowed to close the table during the period. This is because if the frequency of one of the generator sets changes suddenly during the circuit breaker closing process, it is possible that the circuit breaker will fit on a non-synchronous point.

4. How to adjust the inverse power of the Parallel unit?

When the two generator sets are tied at no-load, a problem of frequency difference and voltage difference will occur between the two units. In addition, on the monitoring instruments of the two units (current meter, power meter, and power factor table), the system reflects the actual inverse work. One is the speed (frequency) the inverse work caused by inconsistency, and the inverse work caused by voltage difference, is adjusted as follows:

1. Adjust the inverse phenomenon caused by frequency:

If the frequency of the two units is different and the difference is large, the current of the units with high rotation speed is displayed as positive in the Instrument (current meter and power meter), 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 rotation speed (frequency) of one unit, and adjust the Indicator Based on the power meter, and adjust the indicator of the power meter to zero. The power indicator of the two units is zero, so that the speed (frequency) of the two machines is basically the same. However, when the current meter is still indicated, this is the inverse phenomenon caused by the voltage difference.

2. Adjust the inverse phenomenon caused by voltage difference:

When the power meter indication of the two units is zero and the current meter still has the current indication (that is, a reverse positive indication), you can adjust the voltage adjustment knob of one of the generator sets, depending on the Current Meter and power factor indication. Eliminate the indication of the current meter (that is, adjust it to zero). After the current meter has no indication, adjust the power factor to a lag of more than 0.5 depending on the indication of the power factor table. generally, it can be adjusted to about 0.8, which is the best status.

V. Generator Protection Circuit

1. Inverse work

The inverse work is caused by different rotation speed (frequency) and voltage of the generator set. That is, one generator set carries positive work while the other sets carries negative power. That is to say, the unit with negative power becomes a load (the unit is low in frequency and the rotation speed is inconsistent ). When the voltage is not the same, a unit with a high voltage provides a reactive current and a reactive voltage (the current meter of the unit is positive indication), which is equivalent to in the current power supply system, added a camera group. The Unit with Low Voltage becomes a large load and receives a large amount of reactive current to maintain the voltage balance between the two units (the current meter of the unit is reversed ). During monitoring, the voltage of one unit is increased, or the voltage of the other unit is high or low, resulting in a reverse current of one unit. The current is about 20% of the rated current. Relay action, Trip, alarm, but not stop.

2. overcurrent:

The current power rating of the generator set is certain, and its overload capacity is very low. Basically, it is about 5% of the rated power, and the loading time is 15 ~ 30 minutes, no more than 60 minutes, more than this time, the generator set will be heated, wire insulation will be reduced, it also reduces the service life. Therefore, there is no special requirement for setting the overcurrent protection. The overcurrent protection can be set to 110% of the rated current. When the load test is performed, the current is carried to 110% of the rated flow. Trip, alarm, no stop.

3. overvoltage:

When the generator set is used in parallel, the power supply system is most afraid of oscillation. Once the voltage of the system is increased, the insulation breakdown of power equipment and power supply equipment is easily caused, and the power supply equipment and power supply equipment are paralyzed together. For this reason, all the generators used in parallel are equipped with overvoltage protection, and the set value is 105% of the rated voltage, which is the best. Transient Over-Voltage Relays, trip shutdown, alarm action. (6) splitting and closing circuit

The split and closed loop are connected to the mobile phone and the control loop is automatically tied.

1. Manual splitting and closing: Each unit can be used as the master or waiting for splitting and closing. Manual splitting and closing are used when the unit is manually connected to the vehicle or power supply.

2. Automatic splitting and closing: Each unit can be selected as the waiting unit or the first unit. After the first unit is started, the closing loop is automatically closed, and the Unit is automatically put in and out of the same period. After the same period, the waiting unit will be automatically closed for parallel operation.

3. whether it is manual or automatic closing, once the Unit has reverse work, it will pass through low oil pressure, high water temperature, high water temperature, high oil temperature and overvoltage, all automatically split the unlock columns from the load.

(7) Synchronous Loop

1. When the first machine is switched on, the power supply is sent to the bus. At this time, the bus detects the circuit at the same time and the circuit at the same time. After receiving the signal, the system automatically closes the detection relay at the same time. Send the bus voltage and the waiting voltage to the synchronous control module. The module automatically detects the voltage and speed of the unit. If there is a difference in the speed, the module automatically adjusts the waiting for parallel rotation speed to reach the parallel condition. Find the closing Command issued by the module in the same period after the same period, and then execute the closing command after the Unit receives the command, that is, the two units run concurrently.

2. after the group is tied, the circuit automatically exits during the same period. However, the switch must be manually switched off during the same period to prevent the group from waiting for parallel signals when the group is resolved after the call, the device is automatically put into operation during the same period, so that the Unit is tied again.

(8) Load Distribution

1. When a single machine is running, the Server Load balancer is not put into operation.

2. the Load balancer of each unit after the group is tied together and put into operation at the same time, adjust their own rotation speed to make the average power distribution of the two units. its working principle is as follows, based on the output power of the unit (namely the current size), the rotation speed of the unit is automatically adjusted to balance the load.

(9) voltage adjustment circuit:

1. Before the parallel operation, the voltage of the two units must be adjusted to the same value.

2. After no-load parallel operation, adjust the voltage knob to eliminate the inverse power phenomenon so that the power factor is about 0.8 behind.

3. After the parallel unit is loaded, you can manually adjust the voltage knob according to the load conditions so that the power factor is in the optimal position. You do not need to adjust the knob later.

(10) speed adjustment loop:

1. Before the parallel operation, the speed (frequency) of the two units must be adjusted to the same level.

2. during the parallel operation, you can adjust the rotation speed of the first machine or the waiting unit according to the rotation speed of the table during the same period, so that the rotation direction of the table during the same period is clockwise or counterclockwise. The slower the speed, the better, however, during the same period, the table pointer must be rotated to be tied.

3. After the parallel operation, check whether the current and power of the two units are balanced. If the difference is too large, you can adjust the speed knob and adjust the power of the two units to the same.

(11) instrumentation detection circuit:

1. Before the operation, you must adjust the related instruments to zero, but the power factor table and frequency table are not at zero.

2. During the operation, observe the running status of various instruments and check whether they comply with the regulations (whether the instrument wiring is reversed ).

3. Check the current, voltage, and related instruments to check whether the indicator value is normal.

(12) Startup loop:

1. Check whether the startup loop is normal before the operation.

2. Whether the related components can work normally after startup.

3. Check whether the combination of the boot engine and the host is normal and whether the server can exit.

(13) shutdown loop:

1. Whether the suspension electromagnet and solenoid valve are reliable.

2. Whether to stop automatically when the unit fails.

3. Whether the manual stop loop is complete.

4. When a trip is required, whether the trip is stopped or not.