The synchronization process typically involves the following steps:
Voltage Adjustment: The alternator's voltage is adjusted until it matches the voltage of the bus-bars. This is accomplished by adjusting the field excitation current of the alternator.
Frequency Adjustment: The alternator's speed is carefully controlled to match the frequency of the grid. This is achieved by adjusting the prime mover (e.g., diesel engine or turbine) connected to the alternator. The alternator must be brought to a speed slightly higher (synchronization above synchronous speed) or slightly lower (synchronization below synchronous speed) than the grid's frequency, based on the desired synchronization method.
Matching Phase Angles: The phase angle of the alternator's voltage is adjusted to match that of the bus-bars. This is accomplished by fine-tuning the alternator's speed until it reaches the correct alignment. The phase angle is critically important for preventing large circulating currents when the alternator is connected.
Synchronoscope: A synchronoscope is an instrument commonly used during the synchronization process. It visually indicates whether the alternator is in sync with the bus-bars. When the incoming generator's voltage and frequency are within acceptable limits, the synchronoscope will display a rotating needle that matches the speed and direction of the grid's voltage. When both the needle and the grid markings align perfectly, the alternator is synchronized.
Closing the Circuit Breaker: Once the voltage, frequency, and phase angle of the alternator match those of the grid as shown by the synchronoscope, the circuit breaker connecting the alternator to the bus-bars is closed. This allows power to flow from the alternator into the electrical system.
Synchronization is a crucial process that requires precise control and monitoring to ensure the safe, reliable, and efficient integration of new power sources into the grid. Skilled electrical operators perform this procedure, considering safety and stability requirements, to avoid sudden changes in grid parameters that could disrupt the entire power system.
