A three-phase auto-synchronizer is a device used in electrical power systems to synchronize the frequencies and phases of two or more alternating current (AC) generators before connecting them in parallel to a common electrical grid. Synchronizing generators is crucial to ensure that they work together efficiently and do not cause disturbances or damage to the power system. Here's how a three-phase auto-synchronizer typically operates:
Voltage and Frequency Matching: Before synchronizing generators, it's important to ensure that their voltage levels and frequencies are close enough to avoid sudden voltage or frequency mismatches when connected in parallel. Generators are usually brought to the same voltage level and frequency manually using governor and excitation controls.
Manual Adjustment: Initially, the generator to be synchronized is adjusted using manual controls to match the voltage, frequency, and phase angle of the already running generator or grid. This is done using various controls like the generator's speed governor and automatic voltage regulator.
Auto-Synchronization Process:
Voltage Check: The auto-synchronizer first checks the voltage difference between the two generators. If the voltage difference is too large, the synchronization process may be delayed or halted to prevent abrupt voltage transients.
Phase Angle Comparison: The phase angles of the voltages of both generators are continuously monitored. The auto-synchronizer calculates the phase difference between them.
Frequency Comparison: The auto-synchronizer also measures the frequency of both generators. The frequencies should be very close for successful synchronization.
Synchronizing Signal Generation: Based on the phase angle and frequency comparisons, the auto-synchronizer generates a synchronizing signal when the generators' voltages are in-phase and their frequencies are nearly matched. This signal indicates that the generators are ready to be connected in parallel.
Closure of Circuit Breakers: Once the synchronizing signal is generated, the circuit breakers connecting the generators to the grid are closed. This is typically an automated process controlled by the auto-synchronizer itself.
Synchronizing Process: After the circuit breakers are closed, the auto-synchronizer actively monitors the generators' voltages, frequencies, and phase angles. It continues to make small adjustments to the speed governor and excitation controls of the generators to ensure that they remain in-phase and synchronized.
Parallel Operation: Once the generators are fully synchronized, they are connected in parallel to the grid. They share the load in proportion to their ratings, contributing to the overall power generation.
Continuous Monitoring: The auto-synchronizer continues to monitor the generators' parameters during parallel operation. If any significant deviation in frequency or phase angle is detected, the auto-synchronizer might take corrective actions, such as adjusting the generator controls or even disconnecting a generator if synchronization cannot be maintained.
Overall, the three-phase auto-synchronizer simplifies the process of connecting generators to a power grid while ensuring smooth and stable parallel operation. It prevents sudden disturbances that could otherwise occur due to phase and frequency differences between generators, safeguarding the stability of the electrical power system.