Parallel operation of synchronous generator

The Alternator is really an AC generator. In the alternator, an EMF is induced in the stator (fixed wire) by the effect of the rotating magnetic field (rotor) due to Faraday's law of induction. Due to the modern rotational speed of the field poles, it is also known as the modern generator.

Here, we can discuss the parallel operation of the synchronous generator. When AC systems are interconnected for efficiency, the alternators must also be connected in parallel. There will be more than two synchronous generators connected in parallel to the production stations.

Condition for parallel application of the synchronous generator

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1. The method of providing screen access, display and zoom and infinite channel line beauty is also known as synchronization.
2. Running machines are the machine that changes the load.
3. The incoming machine is the exchanger or machine that you need to list delivery with the system.

The conditions that must be met are

1. The phase sequence of the input motor voltage and the busbar voltage must be the same.
2. The RMS (terminal voltage) line voltage of the busbar or the current machine and the incoming machine must be the same.
3. The phase angle of the two systems must be equal.
4. The frequency of the two terminals (input motor and busbar) must be almost the same. Large transient currents will occur when the frequencies are not nearly the same.

Departure from the above conditions will result in the formation of surges and current. It also leads to unwanted electromechanical oscillation of the rotor which leads to equipment damage.

General procedure for parallel synchronous generator

The following figure shows an alternator (generator 2) paralleling a power system (generator 1). These two machines are to be synchronized to supply power to a load. Generator 2 is almost parallel with the help of a switch, S1. This switch must never be closed without fulfilling the above conditions.

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1. To be equal to the voltages of the terminals. This can be done by adjusting the voltage at the input machine terminal by changing the field current and making it equal to the operating system line voltage using voltmeters.
2. There are two methods for controlling the phase sequence of machines. They are as follows

• The first uses a Synchroscope. It does not actually control the phase sequence but is used to measure the difference in phase angles.
• The second method is the three lamp method (Figure 2). Here we can see three lamps connected to the switch terminals, S1. The lamps are bright if the phase difference is large. The lamps dim if the phase difference is small. The lamps will appear dim and bright together if the phase sequence is the same. The lamps will be bright in progress if the phase sequence is opposite. This sequence of phases can be matched by changing the connections in two phases on one of the generators.

Image Source- Google

3. Next, we have to check and verify the frequency of the system received and running. It must be almost the same. This can be done by inspecting the frequency of dimming and brightness of the lamps.

4. When the frequencies are almost equal, the two voltages (input alternator and operating system) change the phase gradually. These changes can be observed and switch S1 can be closed when the phase angles are equal.

Advantages of parallel synchronous generator

• When maintenance or inspection occurs, one machine can be taken out of service and the other alternators can maintain continuity of supply.
• The cargo supply can be increased.
• During light loads, more than one alternator can be switched off while the other operates at an almost full charge.
• High efficiency.
• The operating cost is reduced.
• It guarantees the protection of the supply and allows an economical generation.
• The generation cost is reduced.
• The failure of a generator does not cause any interruption in the supply.
• The reliability of the entire power system increases.