Generator Protection

Question 1

What is the purpose of the Generator Protection System?

Answer 1

Protects the Main Generator, MPT, UAT, and 345 Bus where main transformer connects

Question 2

What are the power supplies to the Main Gen Protection systems?

Answer 2

U2:
Primary - 2A-2 Normal / 2B-2 Reserve
Backup - 2A-2 Normal / 2B-2 Reserve
U3:
Primary - 3B-2 Normal / 3A-2 Reserve
Backup - 3A-2 Normal / 3B-2 Reserve

MUST BE MANUALLY SWAPPED FROM NORMAL TO RESERVE

Question 3

What actions occur on a Main Generator Lockout?

Answer 3

Generator GCB Trip Open
Generator Field Breaker Trips Open
Main Feed Breakers from UAT Trip Opne
Turbine Trip on loss of load
Stator Cooling Pumps Trip

Question 4

What happens to the Generator following a Turbine Trip?

Answer 4

The turbine Trip does not automatically cause a generator trip.
Generator Trip will occur due to reverse power after VARS run to 0.

Question 5

What causes the Generator Field Breaker to Trip?

Answer 5

Generator Lockout
Overcurrent
LBB

Question 6

What happens to the Turbine after a Generator Trip?

Answer 6

Any generator Trip automatically causes a Turbine Trip

Question 7

Where are teh Generator Lockout Devices reset?

How many are there and how many are needed to cause a trip?

Answer 7

These and Deluge are reset from AEER after the condition clears
There are 2 - either will cause a trip
86 devices are reset by LATCHING in NORMAL when condition is cleared

Question 8

What happens to the Generator Protection System on a Loss of 125VDC Panel 2A-2(3A-2)?

Answer 8

Protection system is “degraded”
On Rx Scram, steam is lost to turbine, generator power eventually reverses and trips the generator after ~15 seconds
OCBs open as expectd but Bus 21 WILL NOT AUTO TRANSFER - field breaker remains closed -
Must manually trip turbine due to loss of 86 device turbine trip
2A SWC Pp will not trip since no control power
Sudden Pressure Relays on TR2 and TR21 lost

Question 9

What happens to Generator Protecton o n loss of 125VDC Panel 2B-2(3B-2)

Answer 9

U2 loses reserve power and B/U normal power
U3 loses normal primary power and B/U reserve power
U2 SPR and Auto Deluge on TR-2 lost if on reserve power
U3 - loss of primary protection scheme - SPR and TR Auto Deluge lost
Generator Lockout is lost
Control power to 22/32 lost

Question 10

What are teh Main Generator Lockouts?

Answer 10

Generator           
           Differential Current
           Neutral Overcurrent (Stator Ground Fault)
           Negative Sequence (Phase issue)
           Reverse Power
           Loss of Field
           Over Excitation
           Load Reject
           Overvoltage
           345kV Backup Relays
           345kV 1(10) Diff Relay (Diff Current on busses)
           Voltage Regulator Trips
Transformer
           SPR
           Backup Distance Overcurrent
           MPT/UAT Diff Current
           UAT Neut Overcurrent
           UAT Lead Differential
           UAT Overcurrent

Question 11

What is Generator Over Excitation?

Answer 11

Compares Terminal Voltage to Frequency:
First Level - 110% overvoltage w/ 15 sec time delay - BP when synced to grid
Sec. Level: 120% overvoltage w/ 2 sec time delay - NEVER BYPASSED

Question 12

What is Generator Load Reject?

Answer 12

High Frequency and Low MW output triggers a generator trip.
This is typically because Yard Breakers trip open since no where to put power

Also performes load reject trip if not tied to grid and UAT breaker closed to plant to prevent overloading UAT