SCREEN GP-PROTECTION 2729780 - Caterpillar

Initial Start-Up
Preparing a generator for parallel operation requires special attention. Before you attempt to parallel units for the first time, check all the units for the following three conditions.
same phase rotation
same alternating current frequency
same voltage adjustment
Check the phase rotation.Units that operate in parallel must have the same phase rotation. There are two methods that may be used in order to determine if the incoming unit and the unit that is on-line have the same phase rotation. These methods are listed below:
using a phase rotation meter
using a set of three light bulbsUse the procedure below to determine the proper phase rotation by using three light bulbs.
Illustration 1 g00695380
When servicing or repairing electric power generation equipment:Make sure the unit is off-line (disconnected from utility and/or other generators power service), and either locked out or tagged DO NOT OPERATE. Remove all fuses.
Connect the light bulbs with rated voltage between the generator leads and the corresponding line phase. For example, connect terminal 1 to line 1 across the open circuit breaker.
Start the units that will be in operating in parallel. Bring the units up to speed. As the units approach the same speed, the lights will start to blink.
If the lights blink in sequence, one of the units is connected backward. In order to correct the problem, stop the units. Remove generator leads 1 and 3 at the circuit breaker. Exchange these generator leads. This reverses the direction of phase rotation. Terminal 2 should always be connected to line 2. Go to 5.
Both generators have the same phase rotation when the lights blink in unison. The first condition of "Initial Start-Up" has been met.
Adjust the frequency.The units that will be operating in parallel must operate at the same speed. Speed is proportional to the alternating current frequency.
Allow each electric set to run under load for about 30 minutes.
Adjust the control in order to give the rated frequency at full load.
Remove the load and check the high idle speed. The high idle speed should be approximately 2 to 5 percent above full load speed for generators that are equipped with droop. If these speeds cannot be obtained, contact your Cat dealer.
For the most consistent results, repeat 2.b and 2.c until the second condition of "Initial Start-Up" has been met.
Adjust the voltage.The potentiometers should be at the initial settings. Refer to Operation and Maintenance Manual, "Voltage Regulators".Note: Make sure that the speed droop is identical for all of the engines before adjustments are made to the generator.
Preset the unit for parallel operation by connecting the current transformer to S1 and S2 of the connector J2. Set potentiometer P1 for quadrature droop in the center position. Apply the rated load. The voltage should drop for 2% to 3%. Switch the positions of the two incoming secondary wires of the current transformer if the voltage increases.
The no-load voltages should be identical for all the generators that are operating in parallel. Connect the generators in parallel. Try to obtain a 0 kW power exchange by adjusting the speed