Generators Flashcards
- Describe the procedure for running up and paralleling an alternator onto the switchboard. (16)
Ensure that no persons are working on the machine, all covers and guards are in place. Ensure sufficient lubrication oil level within the sump.
Ensure that starting and control air is on, fuel supply is available and the cooling system is operational.
Start the lube oil priming pump, check the engine for leaks and that the pressure has risen. Open all indicator cocks, with the fuel supply closed turn the engine on turning gear ensuring all cylinders purge now close indicator cocks.
Disengage turning gear, open fuel supply and start the engine. Ensure the priming pump has stopped and check the machine for leakage.
Set the frequency of the incoming machine to that just higher of the bus bar; ensure the correct voltage and phase rotation is correct.
Bring the machine into synchronism and close the circuit breaker, using the governor controls reduce the outgoing machine and increase the incoming machine. Ensuring that voltage and frequency remain constant whilst balancing out the load.
- Describe the conditions that must be satisfied before paralleling an A.C. generator with the main electrical switchboard. For each condition described explain how it is achieved. (16)
Voltages of both incoming and running generators must be the same. This is achieved by observing the voltmeter and any adjustments required are made through AVR. Frequencies of both incoming and running generators must be the same. This is achieved by observing the frequency meter, any adjustments required are made through governor control provided on the main switchboard.
Voltages of both incoming and running generators must be in phase. This is achieved by observing the synchroscope, any adjustments required are made through governor control provided on the main switchboard.
- a) State the conditions that must be satisfied before paralleling an A.C. generator with the main electrical switchboard. (6)
b) For EACH condition stated in Q3(a) explain EACH of the following:
a) how it is monitored (4)
b) how it is adjusted (6)
a) Voltages of both incoming and running generators must be the same. Frequencies of both incoming and running generators must be the same. Voltages of both incoming and running generators must be in phase.
b)
i) Observe the voltmeter.
Observe the frequency meter.
Observer the synchroscope.
ii) Any adjustments required are made through AVR.
Any adjustments required are made through governor control provided on the main switchboard.
Any adjustments required are made through governor control provided on the main switchboard.
- Describe how to manually couple a second auxiliary generator to the main switchboard and balance out the load.
On the switchboard check the voltage to see if the incoming voltage is same as busbar, if not adjust through AVR.
On the switchboard, check the frequency to see if the incoming frequency is same as busbar, if not adjust through governor control.
Turn on the synchroscope.
Synchroscope must run in clockwise direction, if not adjust through governor control. Allow synchroscope to steadily run at a rate of 4-5 seconds per revolution.
Close the main circuit breaker when synchroscope is at 5 to 12.
Switch off the synchroscope.
Allow generators to run steadily.
With the aid of governor control, increase the fuel if incoming slightly and decrease the fuel of running slightly. This adjustment, will add kW to incoming and decrease kW load from running. Keep adjusting kW load sharing until evenly balanced.
- Explain the procedure to be taken in EACH of the following circumstances in order to prepare a large electrical generator set for maintenance:
a) taking the a. c. generator off electrical load; (6)
b) isolating the machine in order that work may be safely carried out. (10)
a) Before the generator is off loaded for maintenance, a standby generator is started, synchronised and loaded. When it is safe to off load the generator following procedure is adopted to off load this generator making it ready for maintenance. (No.1 maintenance and No.2 being put on)
Gradually shift the load from No.1 to No.2.
When No.2 is fully loaded, open circuit breaker of No.1
Now No.1 is safe to be shut down.
b) For safe maintenance both the alternator and the prime mover will require to be isolated. Prime Mover Isolation:
John Willison IAMI Revision 59
Stop or shutdown the generator and post notices.
Change to manual/ local control.
Close and lock off fuel valve and post notices.
Close and lock off starting air valve and post notices.
Remove the turning bar to engage the interlock.
Isolate the lub. oil and jacket water system.
Alternator Isolation:
Rack out the main circuit breaker, lock in position and post notices.
