PARALLELING (SYNCHRONIZATION) OF GENERATORS

Paralleling or synchronization is the process of making two or more generators the same throughout or identical (synchronous). Synchronization is achieved for auxiliary engines (e.g. diesel generators) and shaft generators on the synchronizing/Bus-coupler section of the main switchboard.

CONDITION FOR SYNCHRONIZATION

For synchronization to be achieved, the two or more generators must be in the same:
Phase, frequency and voltage.
This is one of the most frequently asked questions in the OOW certificate of competency examination.

STEPS FOR SYNCHRONIZATION

Scenario: Two generators are to be synchronized. Assuming Auxiliary Engine 1-MAIN (Generator 1) is already running, and Auxiliary Engine 2- STANDBY (Generator 2) is on Standby.

1. Check the condition of the incoming generator, check for leaks and abnormalities. These checks should be carried out before running the generator, before synchronizing and after synchronizing the generators.
2. Carry out your various checks; Sound the lube oil sump, check the water level in the expansion tank, check the coolant level, check the fuel suction valve and ensure it is open.
3. Check the incoming generator’s panel on the main switchboard. If there is a trip alarm, reset the panel. Without resetting, the generator cannot be synchronized.
4. Go to the Electronic Control Module (ECM), remove from Auto, and push the Stop button then the Run button.
5. Go to the Bus bar, check to see if the generators are in the same frequency, phase and voltage. These are the condition for paralleling. If there is a difference in the frequency of the generators, manually raise or lower the DG-Governor on bus bar.
6. Check the PPU (paralleling and protection unit) of each generators, it displays the condition and parameters of the generator at each time.
7. Go to the synchronizing/bus-coupler section, change the incoming generator from its standby position to Zero and change the synchronizing mode selector to auto.
8. On the synchronizing selector, select the incoming generator’s position.
9. Watch the synchronoscope( Normal rotation- clockwise): in Auto mode, it will automatically close the breaker; in Manual mode, the operator will manually close the breaker at 12 o’clock.
10. On the synchronizing selector, change its position to Zero immediately after the breaker of the incoming generator closes.
11. Both generators are successfully synchronized, Check the PPU and observe the parameters.

After the required need for the synchronized generators have been met, you will need to return to the single generator mode.
To return;

1. Go to the bus bar of the outgoing(standby) generator, press and hold the DG(diesel generator) Deload button
2. Once a shutting sound is heard, release your pushing force on the button.
3. Go to the ECM panel, stop the outgoing generator which is referred to as the Standby generator.
4. On the Standby generator’s ECM panel, put it on Auto.
5. Go to the DG standby selector on the synchronizing/bus-coupler and put it on the standby generator’s position.
6. Check the condition of both the main and standby generators and monitor the load on the main generator.

TROUBLESHOOTING

Setbacks may occur during the synchronizing operation, some of these are:

1. The standby generator is not synchronizing: check if both generators are in the same phase, frequency and voltage. Check if the incoming generator had tripped, reset if need be. Check to see if you had forgotten to select its position on the synchronizing selector.
2. The load on either one of the generator is too much: check to see if the synchronizing mode selector is on auto, doing so allows the PPU to share load by actuating the governors of both generators. Manually actuating the DG- Governor on a generator’s bus bar by raising or lowering the load it is currently taking on.
3. Synchronoscope is rotating anti clockwise: This is as a result of difference in frequency of the generators to be synchronized. It is inconsequential, no need for alarm.
4. Synchronoscope keeps rotating without the breaker closing: Open up the synchronizing section bus bar and check the condition of the circuit breaker. The charge motor operator (CMO) should be discharging, if not gradually charge the breaker with the charging knob provided. Do this gently to avoid breaking the charging knob which will lead to bigger problems.
5. Deload is not working: The fault is from the CMO, open the circuit breaker bus bar, the CMO will be on discharge spring and in manual position. Change it to auto.
6. Reversed power: Reverse power is a situation in which a generator which is designed to generate and give power tends to draw power from the bus bar instead of feeding it. This can lead to blackout. The reverse power trip is one of the protection in the bus bar designed to make a reverse power of little or no effect.