SEAL AS 5J7019 - Caterpillar

The phase sequence of the generator must be equal to the phase sequence of the system in order for the systems to operate in parallel. The phase sequence can be checked by a phase rotation meter. Check the phase sequence at the generator and check the phase sequence at the lines that come from the system bus. Synchronizing lamps can also be used in order to determine the relative phase sequence. Refer to Illustration 1. The correct phase sequence is indicated when the brilliance of the two lamps changes together.The output voltages at the parallel point must meet the following criteria:
the same frequency
the same magnitude
the same phase rotation
the phase angles must coincide with each other. A synchroscope can be used in order to indicate the phase angle. Synchronizing lamps can also be used in order to indicate the difference in the phase angle. The connection that is shown in Illustration 1 will indicate the following conditions:
an in-phase condition
a correct-phase conditionWhen both lamps are illuminated, an out-of-phase condition is present. When both lamps are not illuminated, an in-phase condition is present. The lamps must be rated for two times the voltage that is produced by the transformers. The circuit that is shown in Illustration 1 is the circuit that is used in the following paragraphs. Other circuits can be used in order to indicate the phase angle. These circuits can have one, two, or three lamps.
Illustration 1 g00561706
Each engine in the system must have the same characteristics for regulating speed. The governors must be adjusted in order to give the same speed droop at the full load rating of each generator. Each voltage regulator must include paralleling circuitry. Each voltage regulator must be connected to a paralleling current transformer. Paralleling current transformers must give the same secondary current. The droop current transformer's secondary winding provides a reactive kVA droop signal to the voltage regulator. In order to achieve proportional sharing of the reactive load between the generators on the system, the voltage droop of each generator must be equal. The accidental reversing of the current transformer's wiring will cause the voltage to rise rather than droop. If this occurs during paralleling, stop the unit. Reverse the wires of the droop current transformer at the terminals of the voltage regulator. If the generator set is equipped with a "Unit Parallel Switch", set the switch to the PARALLEL position. Synchronize the generator by adjusting speed (frequency) and voltage slightly higher than the system frequency and voltage. Observe the lamps or the synchroscope. The brightness of the lamps should fluctuate. The lights will be dark when the generator is in-phase. The lights will be bright when the generator is out-of-phase. This fluctuation will occur in cycles of approximately two or three seconds when the engine speed is adjusted correctly. Observe the synchroscope pointer. The synchroscope pointer should rotate in the counterclockwise direction. This rotation will occur in cycles of approximately two or three seconds. When the generator is in-phase, close the