DEHC Flashcards
DEHC Generates electronic signals to position which components:
a) four HP turbine stop throttle valves
b) four HP turbine governor-control valves
c) two reheat stop valves and two intercept valves per LP turbine
Trips the turbine if speed exceed____ of rated speed to prevent exceeding ______.
108%
120%
What are the 4 headers?
Emergency trip header
HP supply header
Normal drain header
Atmospheric drain header
If one input of three fails, _____.
The average of the other two is used to control the turbine.
Reactor trip occurs above _____ when <______ psig on _____ 1/2 trains -or-
_____closed
P-8
<1000 psig
2/3 on 1/2 trains
4/4 TVs closed
OTdeltaT/OPdeltaT runback
In auto:
In manual:
How actuated:
When does it stop?
Ramps down at 200%/minute for 1.5 seconds, rests for 28.5 sec, repeat until condition clears or 235 MW reached.
2/4 delta T channels within 3 % of setpoint.
CD/FW PP trip runback
In auto:
In manual:
How actuated:
If in operator Auto:
Ramps down at 250 MW/min, stops at 700 MW.
If in manual:
Ramps down at 200%/min, stops at 700 MW.
Actuated manually at OWS or with runback PB.
HD PP trip runback:
In auto:
In manual:
How actuated:
In auto: Ramps down at 20 MW/min, stops at 780 MW.
In manual: Ramps down at 200%/min, stops at 780 MW.
Actuated manually at OWS.
FW heater isol runback:
In auto:
In manual:
How actuated:
In auto: ramps down at 100 MW/min, stops at 1050 MW.
In manual: ramps down at 200%/min, stops at 1050 MW.
Actuated manually at OWS.
Single valve control mode.
What does it do?
When used?
Advantages/disadvantages
- All GVs act as one, opening/closing together.
- Used: -<20% power - TV/GV testing -If GV demanded position differs substantially from actual position
- Single admits steam to full arc of HP turbine: more even heating, minimizes thermal stresses, less efficient due to throttling losses.
Sequential valve control mode.
What does it do?
When used?
Advantages/disadvantages
- GV-1, 2 and 3 open together, then GV-4 throttles to control turbine speed after GV 1-3 are full open.
- Used >20% power
- Provides greater efficiency due to less throttling losses.
Operator Automatic/Overspeed Protection Control Controller (OA/OPC) provided trips:
- Overspeed 2/3 >=108%
- EH pressure low 1000 psig
- Watchdog trips: loss of drops 3 and 53 or signal from ETS to OA to generate turbine trip.
ETS controller provided trips:
- Overspeed 2/3 speed >=108%
- Bearing oil pressure low 6 psig
- Condenser low vacuum 10” Hg absolute, can be bypassed to allow turbine to latch without vacuum
- Thrust bearing failure 70 psig
- Watchdog trips, loss of both drop 2 and 52 or signal from OA to trip turbine.
Valve contingency:
____error between GV demand and actual position or ___seconds on 2/2 LVDTs.
On1 GV: ________
On 2 or more GV:__________
5% error between GV demand and actual position or >10 seconds on 2/2 LVDTs.
On1 GV: reject to single valve control
On 2 or more GV: reject to manual
OPC 1 and 2 solenoids are powered from _____. Function is to ______.
Strokes ____ and _____ only.
Prevents ____________.
DC bus 114
Strokes GV and IV only
Prevents turbine overspeed on partial or complete load rejections. Actuates at 103%.
Standby auto EH pump starts at ___
1600#
EH is cooled by ____ and maintains temperature of EH fluid ____ to _____.
WS
110-130F
There are ____ ETS trip manifold solenoid valves and they are (energize/de-energize) to trip.
8
De-energize
What are the 4 feedback loop modes?
Speed/frequency
MW
Impulse
NIS power
EH 5042 directs air to isolate the following three components:
- AO check valves (non-return) close
- ES062s (MSR 1st stage) close
- Spillover valves open
Resonance region for main turbine is ____ to _____ RPM.
800-1200
C-20 AMS permissive
Inputs
Function
2/2 impulse pressure >30%
Arms AMS
P-13 turbine at power
Setpoint and coincidence
Function
1/2 P-imp ch >10%
2/2 P-imp ch <10% to clear
Input to P-7 permissive
C-5 turbine low power rod stop
Setpoint and coincidence
Function
Turbine low power rod stop
Validated P-imp <15%
Stops outward rod motion in auto
