Sequence of Operation of Generator Synchronizing Panel

Automatic Operation

Failure of Utility Power Supply

• Upon failure of the utility power supply, the Automatic Transfer Switch (ATS) will send a signal to initiate the start of Generators. This signal has a delay (typically 2 seconds) depending on the preset value at the timer or at the ATS controller.
• Upon receipt of start signal from the ATS, all the Generators connected to the synchronizing panel will start independently and ramp-up to stabilize their rated frequency and voltage output. The ramp-up time of Generators depends on the model of Generator.
• Out of the multiple Generators, the first one to stabilize its output voltage and frequency will signal its Circuit Breaker to close to supply the dead common bus. Depending on the design of the Generator Synchronizing Panel, the feeder or load breakers are usually close.
• The Synchronizing controller of the Generator Synchronizing Panel will monitor all the Generator’s electrical parameters upon start.
• The second Generator to stabilize its output will synchronize to the first Generator that was already connected to the live common bus. Once synchronized, the second Generator will close its Circuit Breaker to connect to the live common bus.
• Similar to the above operation will follow for the remaining Generators untill all Generators are synchronized at the common bus.

Bus Overload

The priority loading controls at the downstream Automatic Transfer Switch of the Generator Synchronizing Panel prevents the simultaneous transferring of all loads to the Generator. Therefore, this prevents the overloading of the common bus.

Generator Synchronization Failure

If the Generator fail to synchronize after a preset time delay, an alarm will sound and the GSP will continue to attempt to synchronize until signaled to stop by the operator thru manual operation button.

The following events should trigger the sound of alarm and/or shutdown the Generator:

• Breaker Failure
• Overcurrent
• Loss of Field of Excitation
• Reverse Power
• Overcrank
• Overspeed
• Ground Fault
• Overvoltage
• Undervoltage
• Over Frequency
• Under Frequency

Parallel Operation

• After all the Generators are synchronized, the Synchronizing controller will start its power management features. The power management is always active during operation to maintain the base setting of loads between 30% and 70% of generator rated capacity.
• The Synchronizing controller will actively monitor the total load connected on the system and calculate the load percentage on each Generator. Each Generator will share the loads equally.
• If the load on each Generator is between 30% and 70% of its capacity, all Generators will remain connected to the common bus.
• If the load on each Generator decreases to less than 30% of its capacity, the Synchronizing controller will start to send signal to Circuit Breakers to disconnect the Generators one by one, starting from least priority Generator until the load of each of the remaining Generators in parallel to the common bus is more than 30% but less than 70% of its capacity.
• If the load on each Generator in parallel operation increases to more than 70% of its capacity, the Synchronizing controller will start to send signal to Circuit Breakers to connect the standby Generators one by one, starting from highest priority Generator until the load of each Generator in parallel to the common bus is more than 30% but less than 70% of its rated capacity.
• If the total load is less than 30% of the rated capacity of one (1) unit of generator, the Synchronizing controller will disconnect all the Generators except for the highest priority Generator. This priority Generator will stay connected to supply power to the loads.

NOTE: The capacities and requirements of Generators vary from generator to generator. However, there are some widely accepted guidelines. The accepted minimum load is 30% while the accepted maximum load is 60-75%.

It is also worth noting of the dangers of running a Generator on low load or no load. No load operations are acceptable for short diagnostic runs such as checking for proper idle, etc. No load operation should never exceed 15 minutes. Again, this vary from generator to generator so it is advisable to contact the generator manufacturer who will be able to advise on safe low load operation values and durations. Load Bank Test is also recommended once a year where the Generator os run for several hours to eliminate all deposits.

Return of Normal Power Supply

Upon return of Normal power supply, the Automatic Transfer Switch (ATS) will remove the GENSET START signal from the Generator Synchronizing Panel to initiate the opening of all generator breakers.

The running generators will operate at no load for a cool down period preset at the Generator Set Module (usually 5 minutes). After completion of the cool down period, all running generators will shutdown.