Operating the Generator Set The procedures for operating a single generator set (single unit) are as follows: 1. Ensure that the PARALLEL OPERATION-SINGLE UNIT OPERATION switch (fig. 3-19) is set to SINGLE UNIT OPERATION. 2. Position the AMPS-VOLTS selector switch to the required position. Rotate the VOLTAGE ADJUST control to obtain the required voltage. Read the voltage from the VOLTS AC meter.

3. Depress the locking button, and slide the ENGINE MANUAL SPEED CONTROL in or out to obtain the approximate rated frequency; rotate the vernier knob (the knob on the control) clockwise or counterclockwise to obtain the rated frequency. 

NOTE: If necessary, the load may be applied immediately.

4. Operate the engine for at least 5 minutes to warm it up.

5. Apply the load by holding the CKT BRK switch (on the CONTROL CUBICLE) to CLOSE until the CKT BRK indicator lights go out. Then release the switch.

6. Observe the readings from the VOLTS AC meter and the HERTZ (FREQUENCY) meter. The voltage readings should be 120/ 208 to 240/ 416 volts ac (depending on the positions of the AMPS-VOLTS select switch and the voltage change board). Let's say, for example, that you positioned the voltage change board for 120/ 208 volts before you started the generator set. When you position the AMPS-VOLTS selector switch to L2-L0 VOLTS/ L2 AMPS while the generator is operating, the VOLTS AC meter should indicate 120 volts. The PERCENT RATED CURRENT meter will indicate the percent rated current (not more than 100 percent) between generator line 2 and neutral. The HERTZ (FREQUENCY) meter should indicate 50 or 60 hertz. The KILOWATTS meter should indicate no more than 100 percent with the HERTZ (FREQUENCY) meter showing 60 hertz. Readjust the voltage and frequency, if necessary.

7. Observe the KILOWATTS meter. If the meter indicates that more than the rated kilowatts are being consumed, reduce the load.

8. Rotate the AMPS-VOLTS selector switch to each phase position and monitor the PERCENT RATED CURRENT meter. If more than the rated load is indicated for any phase position, reduce or reapportion the load.

9. Periodically (not less than once per hour), monitor the engine and generator indicators to ensure their continued operation.

10. Perform any "during operation" preventive checks according to your checklist. When in operation, the generator set should be monitored periodically (at least once an hour) for signs indicating possible future malfunctions. After the warmup, the lubricating oil pressure should remain virtually constant. Check and record the level of lubricating oil while the engine is running normally. If any significant changes occur in the oil pressure, notify the maintenance personnel. Check and record the coolant temperature of the normally running engine. Notify maintenance personnel if the coolant temperature changes significantly.

Learn the sounds of a normally running generator set so that any unusual sounds indicating the possible start of a malfunction may be detected early enough to avoid major damage.

Stop the operation immediately if a deficiency that woulddamage the equipment is noted during operation.

OPERATING PROCEDURES FOR PARALLELING GENERATORS  This section will include procedures for paralleling generators, removing a set from parallel operations, and stopping generator set operation. 

NOTE: These procedures assume that one generator set is on line (operating and connected to the distribution feeder lines through the switchgear). The set that is to be paralleled is designated the incoming set (fig. 3-20).

CAUTION When you are operating generator sets in parallel, they must have the same output voltage, frequency, phase relation, and phase sequence before they can be connected to a common distribution bus. Severe damage may occur to the generator sets if these requirements are not met.

Adjusting the engine speed of the incoming set while observing the output frequency and the

Figure 3-20.- Parallel operation connection diagram. SYNCHRONIZING LIGHTS (fig. 3-19) will bring the phase and frequency into exact agreement. As the phase and frequency approach the same value, the SYNCHRONIZING LIGHTS will gradually turn on and off. When the blinking slows to a rate of once per second or slower, close the main circuit breaker of the incoming set while the SYNCHRONIZING LIGHTS are at a point of being dark. The phase sequence relates to the order in which the generator windings are connected. If the phase sequence is not correct, the SYNCHRONIZING LIGHTS will not blink on and off together. When the incoming set is first connected to the load through the appropriate switchgear (fig. 3-20). you should observe one of four occurrences. When the phase sequence, voltage, frequency, phase, and engine performance are the same, the changeover will be smooth with only the slightest hesitation in engine speed; if each output is slightly out of phase, one of the engines will shudder at the point of changeover; if the phase sequence or voltage levels are incorrect, the reverse power relay will trip on one of the generator sets and open its main circuit breaker contactors; if the incoming generator set loses speed significantly or almost stalls, the incoming engine may be defective.

CAUTION Should either generator set lose speed, buck, or shudder when the incoming set is connected to the distribution feeder lines, immediately flip the CKT BRK switch of the incoming set to open, and then recheck the paralleling set-up procedures.

Refer to figures 3-19 and 3-20 to set up the generator sets for parallel operation. 

WARNING When performing step 1, make certain that the incoming set is shut down and that there are no voltages at the switchgear terminals being connected to the incoming set. Do not take anybody's word for it! Check it out for yourself! Dangerous and possibly deadly voltages could be present. Take extreme care not to cross the LO (neutral) with any of the other phases (L1, L2, or L3).