TEE 2428717 - Caterpillar

If Unit A had been operating alone carrying full load, the system frequency would be 60 cycles as shown by Line "A" at 60 cycles and 100% load. Now, if the frequency of Unit B is adjusted by the engine speed control to be equal to that of Unit A and the circuit breaker of Unit B is closed, the system would be operating under the following conditions:1. Unit A is at 60 cycles and 100% load.2. Unit B is at 60 cycles and 0% load. The characteristic of the governor of Unit B at this time is shown by the dotted line B.In order for Unit B to carry load, it is necessary to advance the speed setting of the governor. If it is advanced to the full load position, the governor characteristic of B will coincide with the characteristic of A. Since the load on the system was 100% of one unit, no change was made in total load, and the available capacity is now 200%, the system will operate at 50% load on each unit, and 60.9 cycles for two units of equal capacity (Point E). For units of unequal capacity, the load will be divided in proportion to the ratio of