PIN-SPRING 8T2276 - Caterpillar

The operation of one electric set is not complicated. Increase the governor setting and the speed increases. Decrease the governor setting and the speed decreases. Increase the voltage level setting and the voltage increases. Decrease the voltage level setting and the voltage decreases. When two or more electric sets are connected in parallel, making changes to governor or voltage regulator settings gives entirely different results.
Same number of phases.
Same phase rotation.
Same frequency.
Same voltage.
Same voltage droop.As discussed in the section on governors, it is not necessary for the mechanical or hydraulic governors to have the same speed droop. However, it is necessary for all the governors of units being paralleled to have 3% speed droop except one. This one governor can have 0% speed droop and be used to control the frequency of the system. The paralleling operation is performed with the assistance of a synchroscope or synchronizing lights to show when the frequencies of the generators are the same. With the synchroscope, paralleling is performed with the pointer, in a vertical position. With synchronizing lights, paralleling is performed when the lights are dark. Refer to the Operation and Maintenance Instructions for the electric sets being paralleled for more details.When generators have been paralleled at no load and no operations have been performed except closing the circuit breaker, the machines are "floating" on the line with no power being transferred either between them or to a load. When a load is connected to the system, power is supplied from the paralleled units. If they all have the same rating and governor speed droop characteristics, the load will be divided equally among them. Any differences in kilowatt loading should be equalized by adjusting the governor controls. To increase the kilowatt load on a unit, the governor control should be advanced farther in the direction to increase speed. For small movements of the governor control, the change in system frequency will be negligible or zero. However, changes in kilowatt load among the engines may be appreciable. To insure balanced kilowatt loading of several electric sets, a separate kilowatt meter for each one is extremely helpful.There is a misconception that an generator operating in parallel can have its kilowatt load changed by changing its excitation or magnetizing power. It seems logical that if the voltage level control setting is increased there will be an increase in kilowatt loading of the generator in a manner similar to that experienced when an generator is operating by itself. This is not true.If the magnetizing power of a generator is increased beyond the value required to maintain the voltage of the generator at the same value as the system voltage while the generator is delivering the amount of power determined by the engine governor setting, the excess magnetizing power goes out from the generator into the system as MAGNETIZING POWER. This fact shows up as an increase in amperes being furnished by the generator.
Illustration 1 g01059119
Consider an over excited generator operating in parallel into a resistive load. The