Run each parallel generator individually with no load. Adjust the operating voltage of each generator for 2 to 4% above the nominal full load voltage for the system. Rotate the voltage adjustment "P2" in a clockwise direction in order to increase the voltage. Rotate the voltage adjustment "P2" in the counterclockwise direction in order to decrease the voltage.
Note: The no-load voltages must be identical on all generators that are intended to run in parallel.
Note: Before adjusting the reactive droop, make sure that the speed droop is identical for all engines. Refer to the manual for the engine in order to adjust the setting for the speed droop of the engine.
Note: Ensure that the Current Transformer (CT) that is used for droop is connected to terminals "S1" and "S2". Ensure that the Potentiometer "P1" (quadrature droop) is positioned in the center.
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| Illustration 1 | g01763729 |
A droop CT that is correctly wired to the R438 and phase U(a) on the generator. (1) Droop CT | |
Apply the rated load at the reactive 0.8 Power Factor (cosΦ = 0.8 inductive) individually to each machine. The voltage output from each generator should droop (decrease) by approximately 2 to 4%. The voltage should then stabilize at the desired operating voltage. Adjust "P1" for the correct voltage droop with the reactive load. Turning "P1" clockwise will increase droop. Turning "P1" counterclockwise will decrease droop. A higher droop will result in a more stable parallel operation. A higher droop may also result in higher voltage fluctuations between load and no load conditions. This may be undesired by some customers.
Note: If the voltage increases when the reactive load is applied, ensure that the phases have not been reversed. Also, ensure that the polarity of the CT has not been reversed on the S1 and S2terminals.
Parallel the machines with no load. Adjust the engine speed in order to obtain an equal load sharing (0 kW). If there is reactive current flow between the machines and the engine speed is matched, adjust the voltage setting of one of the machines with the "P2" potentiometer. Minimize the current that is circulating between the machines. After this is done, do not adjust the voltage settings with the "P2" potentiometer on any machine.
Apply the rated reactive load. The adjustments will only be correct if a reactive load is available. If it is required, adjust the engine speed in order to match the kW engine load for each engine. Divide the load for the engines proportionally. Adjust "P1" quadrature droop in order to match the reactive current for each generator. Turn the "P1" potentiometer counterclockwise in order to remove the reactive VAR from the machine. Adjust "P1" until the current and power factor match on each machine. Alter the load in order to confirm that the operation is stable throughout the load range. If the circulating currents are only minimized under certain load conditions, confirm that the speed droop of the engine is correctly adjusted. Also, confirm that the speed droop is equal on all machines. Verify that the voltages match at no load on all generators. Readjust the equipment if it is necessary. Then repeat the adjustment for voltage droop until sharing of the reactive current is acceptable.