SHAFT 8R3252 - 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.The phase rotation of the paralleled units must be equal. Two methods are used to determine if the phase rotation of the incoming unit is equal to the phase rotation of the on-line unit. These methods are listed below.
Phase rotation meter
Set of three light bulbsThe procedure for determining the proper phase rotation is described below.
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. 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 exchange reverses the direction of phase rotation. Terminal 2 should always be connected to line 2. Go to 5.
When the lights flash in unison, the phase rotation is equal. The first condition of "Initial Start-Up" has been met.
Adjust the frequency.The speed of the paralleled units must be equal. Speed is proportional to the alternating current frequency.
Allow each electric set to run under load for about 30 minutes.
Adjust the governor control in order to give 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 governors that are equipped with droop. If these speeds cannot be obtained, contact your Caterpillar 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.There are two different methods for reactive power equalization.
Reactive droop compensation
Cross current compensation In the reactive droop compensation, the voltage regulator causes an individual generator output voltage to change in proportion to the reactive current. The reactive current is measured with a current transformer (CT).The reactive current can be either lagging or leading. As the lagging reactive current increases, the voltage regulator will cause the generator output voltage to droop proportionally. As the leading reactive current increases, the voltage regulator will cause the generator output voltage to rise proportionally.This method will tend to reduce the reactive current for the better KVAR sharing with other units. The reactive droop compensation is a standard method on the Caterpillar generator sets. The following procedure for voltage adjustment is for the reactive droop compensation.In the cross current compensation, the voltage regulator is forward biased by the difference in reactive current outputs of the