DEHC

Question 1

With no feedbacks in what is DEHC using to control MW? MW in?

Answer 1

It has a calculated valve position that equates to MW MW transducer feeds back actual MW

Question 2

Power supply to DEHC

Answer 2

PPC ups - battery charger - 12i Permanent Magnet Generator (PMG)

Question 3

DEHC, what conditions put you in load control ? Speed control?

Answer 3

• either gen output bkr closed and MOD closed
• both gen output bkrs open or MOD open

Question 4

What are program ramps on DEHC?

Are they bypassable?

Why would you do this?

Answer 4

• loss CWP
• loss MFWP
• loss #2 HDP
• Yes, on plant startup

Question 5

What trouble light on HMI of DEHC will be illuminated < 600 rpm? Why?

Answer 5

24 vdc per supply trouble, PMG not supplying normal voltage because Generator not spinning fast enough

Question 6

What is being displayed on following load values? Setpoint Target Actual

Answer 6

• what DEHC thinks MW is - what target MW are - what MW transducer says actual MW are(feedbacks)

Question 7

How many speed channels are there on DEHC? What will happen if they are lost in speed control? Load control?

Answer 7

3 The turbine will Trip (no indication of actual speed) Nothing (protected by mech overspeed, and being synced to grid)

Question 8

What happens at a critical speed (DEHC)? What if you try and stop the turbine ramp at a critical speed?

Answer 8

• speed is automatically raised to 200 rpm/ min while in critical speed, and you are unable to stop ramp

Question 9

Can you remove speed in feedback on DEHC?

Answer 9

No

Question 10

Ca you stop any programmed turbine load reduction by pressing “hold”?

Answer 10

Everything but a run back

Question 11

What is the low signal select comparing choosing between?

Answer 11

Valve position limit VS. Speed error signal (speed loop) Or Modified error signal (load loop)

Question 12

What are the signals that provide overspeed protection via the OPC? What is required to get those signals ?

Answer 12

OPC channel > 103% (CV and IV close->101%) LDA (close CV and IV, 2 sec after good-> open) - output bkrs open - > 22% equivalent power (LP turbine inlet Press) - % turb load > % gen load by 30%

Question 13

List turbine run backs

Answer 13

• OTAT (C-3), 1% lower Trip
• OPAT (C-4), 1% lower Trip
• Stator cooling problem
  
  • d/p < 16 # FS-1 or FS-2 for > 5 sec (give stby pump chance)
  • cut in enabled
  • MG current > 4494 amps (15%)
  • MOD closed

Question 14

What is difference between single valve control and sequential? When is each used?

Answer 14

Single- all valves throttle together acting as one Used, during S/U and valve testing Sequential- 3 valves open, last one throttled Used, during normal operation