GEAR (25 T) 6N4752 - 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 adjustmentSeveral methods may be used to parallel generators. The preferred method is the utilization of a switch gear that uses automatic paralleling.A method of manually paralleling generators which requires thorough understanding of the process is outlined below.
Check the phase rotation.Units that operate in parallel must have the same phase rotation. There are two methods that may be used 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. To correct the problem, stop the units. Remove generator leads 1 and 3 at the circuit breaker. Exchange the generator leads which reverse 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" had 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 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 "Initial Start-Up" had been met.
Adjust the voltage. The generator voltage regulator should be programmed to the nominal values. Refer to Operation and Maintenance Manual, "Voltage Regulators".Note: Make sure that the speed droop is identical for all the engines before adjustments are made to the generator.
Program the reactive droop for the voltage regulator to approximately 2%. Initially program the same value on all generators which will be paralleled.
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 of the generator.