EDGs Flashcards
What is the function of the EDGs, what causes an autostart and when will the output breakers close?
Function of the EDGs is to provide alternate source of power for the ES buses (A-3/A-4) in the event of a loss of normal power
EDGs will auto start on asosciated UV on A-3/A-4 (< 3300 V for 2 sec), UV on B-5/B-6 (< 430 V for 8 sec) and ES 1 or 2 will start both
Output breakers will close on UV condtion of associated bus only
What is the design basis for EDGs?
EDGs are rated at 4160V, 2750 KW, 900 RPM, 20 cylinder and designed to start and be at rated speed and voltage within 15 seconds to provide power to ES buses.
What are the TS requirements for the air start system?
Starting air receiver pressure must be > 175 psig. This ensures 5 starts from the bank. < 158 psig renders the EDG inoperable.
Only requires one starting air receiver to be operable.
What are the TS requirements for the fuel oil system?
TS 3.8.3 requires T-57s to be greater than 20,000 gallons (138”). < 17,140 gallons renders the EDG inoperable. TS entry (3.8.3) required when between 17,140 and 20,000 gallons.
> 20,000 gallons gives 3.5 days EDG run time per tank.
What are the 4 lube oil systems for EDG and their purpose?
Main lube oil loop - lubricates all engine areas except pistons and wrist pins
Piston Cooling - cools and lubricates the pistons and wristpins
Scavenging - provides cooled and filtered lube oil for the main and piston cooling oil loops
Soakback - AC pump maintains engine ready for fast start by warming and filtering lube oil and circulating through the engine. Other pumps (AC & DC) cools turbo bearings.
What is the relationship between positive crankcase pressure device and the low lube oil pressure switch?
The positive crankcase device will trip the EDG @ 0.8 to 2.5” when aligned and drops the oil from the low lube oil pressure switch which then electrically shuts down EDG via K11 relay.
What temperatures cause the EDG exhaust fans to autostart?
A and C start @ 90 degrees F. B and D start at 105 degrees F.
How is level maintained in the T-57s and what is the required inventory?
Level is maintained by gravity through duplex filters from Bulk Storage tank (T-25). Level is maintained > 160” normally and must be maintained > 20,000 gallons per TS.
What indications are provided with the fuel oil filter system and what do they mean?
Normally the sightglass closest to diesel is full which indicates fuel system is primed and ready for start. With EDG Fuel oil flow will be through the 10# check valve which improves fuel injector performance.
When filter clogged or other issue occurs, the 60# check valve flow path will be aligned to provide overpressure protection. This would be indicated by the other sightglass full and closest one empty.
Describe the operation of the fuel oil transfer pumps and day tank?
Fuel oil transfer pumps maintain 180 - 240 gallons and will alarm @ 155” if maintained > 3 min.
What is the purpose of the speed droop setting?
Speed droop lowers engine speed as load is increased and provides stable load sharing when tied to the grid.
What temperature does the immersion heater maintain and what is the minimum lube oil temperature required for operability per limits and precautions?
Immersion heater maintains 125 - 155 degrees F. Minimum temperature of operability for lube oil is 85 degrees F.
Describe the EDG start sequence.
What setpoints do the EDG air start compressors control pressure?
186 - 200 psig
What conditions are required for autostart of EDG?
K11 not energized
engine select not in maintenance
DG lockout relay not energized
C10 control switch not in LO
DG Bkr not in PTL (For breaker to close)
What is the auto start sequence of the EDG?
What conditions cause the emergency trip relay (K11) to energize?
What all happens when 300 rpm is reach following an EDG start?
What conditions de-energize the start pilot relay (K8)? What effect does this have?
When de-energized, the governor run solenoid is de-energized
What conditions will energize the EDG lockout relay?
What is required for diesel to be operable per TS 3.8.3?
