How to manually synchronize two generators.

 Synchronizing Generators: Using Synchroscope and Synchronizing Lights

Synchronizing two generators or synchronizing a generator to the grid is done with the help of a synchroscope and synchronizing lights. 

Synchroscope and Synchronizing Lights


Conditions for Synchronization:

Certain conditions must be met for successful synchronization of two alternators. They are listed below.

Ø  Phase Sequence - It is important that both generators are rotating in the same direction with ABC sequence.

Ø  Voltage Magnitude - It is important that the voltage produced by both generators should be of the same magnitude. This ensures that the incoming generator doesn't absorb reactive power and be motored by the running generator.

Ø  Frequency - The frequencies of the generators must match to avoid in high acceleration and deceleration of the prime mover.  This can lead to increased transient torque.

Ø  Phase Angle -  Ensuring that the phase angle is the same is crucial to prevent a fault similar to a short circuit.

 



Synchronization Procedure:

1) Begin by checking if the voltage from the incoming generator matches that of the bus bar. If not, adjust the alternator's exciter current to raise the voltage.  This adjustment can be done using the raise and lower button or knob on the generator control panel.

2) Verify that the frequencies of both generators match using the synchroscope. The rotation speed of the synchroscope's pointer indicates the difference in frequency between the incoming and running generator. A clockwise rotation (Fast) means the incoming generator is running faster than the running generator, while an anti-clockwise rotation (Slow) indicates the opposite. When the frequencies match, the pointer stops rotating.

It's common practice for the incoming generator to have a slightly higher frequency than the running generator to allow the incoming generator to take on the load. When you achieve this, the synchroscope's pointer would rotate slowly in a clockwise direction, allowing you to close the breaker before the pointer reaches 12 o'clock, typically at 11 o'clock. Do not close the breaker now !!!

The speed of the incoming generator can be adjusted by putting governor control on Droop mode and pressing the increase or decrease button. On some synchronizing panels it says Governor Raise and lower


3) Now monitor the synchronizing lights carefully they should be blinking slowly now. When they go dark, it indicates that both generators have same phase angle.

4) Close the circuit breaker of the incoming generator when the synchronizing light bulbs goes dark, and the synchroscope pointer is close to 12 o'clock.

5) After synchronization, check the load sharing between the two generators. If necessary, balance the load using the exciter raise and lower controls on the generator control panel. On some synchronizing panels it says Increase and Decrease.

 

Note: The position of the pointer on a synchroscope indicates the phase angle between the two systems. 12 o’clock means both generators are in phase while 6 o’clock indicate that both generators are 180 degrees out of phase.  The rotation speed and direction give us an idea on the difference in frequency.

5) Check the load sharing between the two generators. as necessary to balance the load between the two generators with the raise and lower button.

Final Note: The synchroscope's pointer position reflects the phase angle between the two generators.  The pointer at 12 o'clock indicates that both generators are in phase, while 6 o'clock indicates that both generators are 180 degrees out of phase. Additionally, the rotation speed and direction of the synchroscope pointer provide insights into the difference in frequency between the generators.


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