GFES Components Flashcards
VARs in
infinite grid
Generator voltage less than grid voltage
becoming reactive load
VARs out
infinite grid
Generator voltage more than grid voltage
supplying reactive load
MW out
infinite grid
supplying real load
MW in
infinite grid
becoming real load
(motoring the generator)
How do VARs affect amps?
infinite grid
Closer to zero (in or out) = fewer amps
Farther from zero (in or out) = more amps
How do MW affect amps?
infinite grid
More MW = more amps
generator frequency higher than grid frequency
infinite grid
generator supplies load to sync
generator frequency lower than grid frequency
infinite grid
grid supplies load to sync
(motoring the generator)
Generator voltage regulator up
excitation goes up
VARs up
Generator voltage regulator down
excitation goes down
VARs down
Motor-Generator Sets
Power Out =
P-out = P-in - losses
Power Factor Trends via VARs
When VARs in or out = zero, Power factor = 1
As VARs get farther from zero (positive or neg, in or out), power factor lowers
Always between 0 and 1
VARs for paralleled generators
isolated electrical bus
Add generator VARs together
(VARs going in are negative numbers)
Total net VARs will stay the same
If one generator increases/decreases VARs, the other will change to maintain the same total net VARs
Throttling ≠ Pump Speed
(pump laws do not apply)
Air
Throttle valve closes, backpressure ↑, amps ↑
Throttle valve open, backpressure ↓, amps ↓
Throttling ≠ Pump Speed
(pump laws do not apply)
Liquid
amps ∝ ṁ
Throttle valve open, V̇ ↑, amps ↑
Throttle valve closed, V̇ ↓, amps ↓
Temperature ↓, density ↑, ṁ ↑, amps ↑
Heat produced by current
Heat ∝ current squared
Don’t forget the ambient temp!
Isochronous Mode
speed (frequency) is constant regardless of load on generator
If speed goes up, ONLY Hz increases; everything else stays constant
Droop Mode
Speed (frequency) lowers as load on generator increases
Thermocouples
If the reference junction temperature increases due to ambient conditions, then indicated temperature will…
decrease
(reduces ΔT)
(T-ref typically colder than T-measuring)
Thermocouples
If the reference junction temperature decreases due to ambient conditions, then indicated temperature will…
increase
(increases ΔT)
(T-ref typically colder than T-measuring)
An open circuit in a thermocouple causes indicated temp to fail…
to reference junction temp (low).
(voltage difference → 0)
A short circuit in a thermocouple causes indicated temp to fail…
to reference junction temp (low).
(voltage difference → 0)
RTD stands for…
How does it work?
Resistance Temperature Detector
change in electrical resistance ∝ temperature
An open circuit in an RTD causes indicated temp to fail…
high
(open circuit seen as large resistance → maximum temp)
A short circuit in an RTD causes indicated temp to fail…
low
(short circuit seen as very low resistance → minimum temp)
RTD vs Thermocouple
RTDs are better suited for __________ temperature bands
(small or large)
small
RTD vs Thermocouple
RTDs have ___________ output voltage which means…
(higher or lower)
higher
…less extra equipment needed to boost output signals
RTD vs Thermocouple
RTDs _________ require reference junctions
(do or don’t)
don’t
RTD vs Thermocouple
RTD circuitry is __________ tolerant to electrical noise
(more or less)
more
RTD vs Thermocouple
RTDs have an _____________ sensitivity to small changes in temperature
(increased or decreased)
increased
RTD vs Thermocouple
RTDs are __________ accurate then thermocouples
(more or less)
more
RTD vs Thermocouple
Thermocouples are __________ rugged than RTDs
(more or less)
more
RTD vs Thermocouple
Thermocouples are well suited for ____________ temperature bands
(large or small)
large
RTD vs Thermocouple
Thermocouples give a ____________ response to temperature changes
(fast or slow)
fast
(sensing wires drawn very thin)
Bourdon Tube
Changes in atmospheric pressure ________ affect readings
(will or won’t)
will
(tube expansion is against atmospheric pressure; e.g. if atmospheric pressure goes up by 5#, then indicated pressure goes down by 5#)
Bourdon Tube
If ambient temperature goes up, indicated pressure will…
go up
(tube becomes more flexible)
Bourdon Tube
If ambient temperature goes down, indicated pressure will…
go down
(tube becomes less flexible)
With NO density compensation, indicated flow of a gas (steam) will be ________________ than actual flow
(higher or lower)
lower
(higher density = higher mass flow rate = more steam = more reactor power)
A steam flow measuring instrument uses density compensation to convert _________________ into ____________________
volumetric flow rate; mass flow rate
A steam flow measuring instrument uses density compensation and square root compensation to convert the differential pressure across a flow element to flow rate in lbm/hr.
The purpose of square root compensation in this flow measuring instrument is to convert ________ to __________.
differential pressure; volumetric flow rate
In a venturi flow detector (or other D/P-type flow detector), how does D/P follow flow?
Flow ↑, D/P ↑
Flow ↓, D/P ↓
D/P flow detectors measure flow using the principle that the flow rate of a liquid is…
directly proportional to the square root of the D/P
Gas Amplification Curve
Region I
Recombination Region
(not used for much)
Gas Amplification Curve
Region II
Ionization Region
(least sensitive, most accurate region)
(used for rad detectors, Intermediate and Power Range neutron detectors)
Gas Amplification Curve
Region III
Proportional Region
(gas amplification factor ∝ applied voltage)
Gas Amplification Curve
Region IV
Limited Proportionality Region
(not used for detector operation)
Gas Amplification Curve
Region V
Geiger-Mueller Region
(most sensitive, least accurate region)
(Geiger counters; cannot distinguish between types of particles; pulse height is independent of type of radiation)
Gas Amplification Curve
Region VI
Continuous Discharge Region
(can’t be used for rad detection)
Specific Ionization Pulse Height
Why is it important?
Different types of particles produce different pulse heights when detecting ionization pulses.
Rad Detectors
In a proportional counter, what does a discriminator do?
Can be set to only read larger pulses produced by neutrons
(excludes other radiation types)
Scintillation detectors convert radiation energy into light by a process known as…
luminescence
(crystals called phosphors)
A source range NI detector normally uses what kind of detector?
proportional counter
Intermediate and power range detectors use what kind of detector?
ionization chamber
The intermediate range NI detector uses a/an _______________ ion chamber
(compensated or uncompensated)
compensated
The power range NI detector uses a/an _______________ ion chamber
(compensated or uncompensated)
uncompensated
(neutron to gamma ratio so high that gammas are insignificant)
Source range detection is measured in…
counts per second
Intermediate range is measured in…
amps (or percent power)
Power range is measured in…
percent power
How does core voiding affect Nuclear Instrumentation?
moderator is displaced → more neutron leakage → readings initially increase
(then decrease once K-eff is dramatically lowered by loss of moderation)
Which radionuclides might we expect to see in the case of fuel cladding failure?
Iodine-131, Cesium-138, Strontium-89
For wet reference leg, what is the relationship between temp/pressure and level indication?
ρ ↑, L-indicated ↑
(temp/press ↓, D/P ↓)
ρ ↓, L-indicated ↓
(temp/press ↑, D/P ↑)
In an open loop system, the controlled variable _________ used to adjust any of the inputs to the process.
(is or isn’t)
isn’t
In a closed loop system, the controlled variable _________ used to adjust any of the inputs to the process.
(is or isn’t)
is
What is the deadband for a bistable controller?
It is the region between the point when a controller has turned off and the point where the input reaches the setpoint again. Prevents oscillation around the setpoint.
Example:
Oil temperature in a HX rises above the 125 setpoint. Cooling water flow increases. Once the temperature comes down to 115, the controller returns cooling water flow to previous rate.
The deadband is the time between the oil temperature hitting 115 and when it rises to 125 again.
What is the proportional band of a controller?
the ratio of the amount of change possible in the controlled variable to the amount of change possible in the final control element (in %)
input/output
(inverse of gain)
What is the gain of a controller?
the ratio of the amount of change possible in the final control element to the amount of change possible in the controlled variable (in %)
(factor by which magnitude of error signal will be increased)
output/input
(inverse of proportional band)
What is offset in a controller?
the deviation that remains after a process has stabilized
(difference between setpoint and steady-state value of the controlled parameter)
What is deviation in a controller?
Difference between the setpoint and actual value (a.k.a. “error”)
What is feedback in a controller?
Info on the controlled variable sent back to the controller for finer control
Example:
current control valve position might feed back to controller
How does the proportional mode of control work?
throttling control; linear relationship
valve movement ∝ amount of signal deviation
matches supply to demand; parameter stabilizes at “new setpoint”
positions valve at full open, full closed, or intermediate positions
How does integral control work?
(a.k.a. reset control)
magnitude of output dependent on magnitude of input
large error = valve moves quickly
small error = valve moves slowly
controlled variable returns to setpoint following a disturbance; eliminates offset error
slow response to error signal; might initially allow a large deviation, leading to system instability
How does proportional integral control work?
combines proportional and integral
output produced as soon as error signal exists; quickly repositions final control element
eliminates slow response of integral and residual offset of proportional
What problem is common with proportional integral controllers?
reset windup
large sustained error causes controller to drive to its limit to restore system control; causes large oscillations when restoring to setpoint
not well suited for processes that are frequently shut down and started up
How does proportional derivative control work?
controller responds to rate of change of error signal, not just amplitude
controller output initially larger in direct relation with error signal rate change → final control element positioned to desired value sooner
reduces initial overshoot of measured variable; not susceptible to reset windup
How does proportional integral derivative control work?
used for processes that can’t tolerate continuous cycling or offset error and require stability
quick stabilization; return to setpoint; reduces initial overshoot and cycling period before stabilizing at setpoint
EDG Droop mode is used for…
starting and paralleling the EDG to a bus for testing
load changes affect speed; backed up by mechanical governor
% speed droop = (no Load speed - full load speed) / no load speed
EDG isochronous mode is used for…
emergencies when EDG is only source of power to vital AC bus
controller returns EDG to setpoint for 60 Hz for any change in load
(loads sequenced on to minimize impact on EDG)
Wet Reference Leg
How does indicated level relate to the pressure inside the vessel?
Wet Reference Leg
How does temperature change in the reference leg affect indicated level?
Temp ↑, ρ ↓, D/P ↓, L-ind ↑
Temp ↓, ρ ↑, D/P ↑, L-ind ↓
What is the positive space charge effect associated with a gas-filled radiation detector?
Pulse amplitude from ionization is reduced because positive ions form a cloud around the positive electrode. Electric field strength reduces, so there aren’t as many secondary ionizations.
A typical alpha particle produces free electrons in a gas-filled radiation detector primarily by…
electrostatic attraction of bound electrons
Which pair of radiation detector types are the most sensitive to low energy beta and/or gamma radiation?
Geiger-Mueller and scintillation
Rule of Thumb for Makeup Valves & Controllers
(works 90% of the time)
fail closed valve = reverse acting controller
fail open valve = direct acting controller
(controller could be a different component, e.g. detector, valve, etc.)
Rule of Thumb for Drain Valves & Controllers
(works 90% of the time)
fail closed valve = direct acting controller
fail open valve = reverse acting controller
(controller could be a different component, e.g. detector, valve, etc.)
Demineralizers
What is breakthrough?
the point at which the ionic impurities at the demineralizer exit start to show resin exhaustion
Demineralizers
What is leakage?
the very small (nearly undetectable) amounts of undesirable ions that continuously pass through the demineralizer without being exchanged
How are cation beds regenerated?
with an acid
How are anion beds regenerated?
with a base
What is demineralization factor (or decontamination factor)?
a direct measure of demineralizer efficiency
DF = inlet conductivity / outlet conductivity
OR
DF = inlet contamination level / outlet contamination level
Demineralizers
What does a low D/P indicate?
reduced efficiency or channeling
Demineralizers
What does a high D/P indicate?
excessive buildup of solids
(or excess flow which could reduce ion exchange rates, break apart resin and cause resin fines, or cause channeling)
How does a crud burst affect demineralizer performance?
causes more blockage by solids, lower flow, higher D/P, and more radiation
How does raising the fluid temperature affect demineralizer performance?
causes resin to release boron
How does lowering the fluid temperature affect demineralizer performance?
causes resin to hold more boron
(basically dilution: positive reactivity addition)
How should we determine what a demineralizer’s D/P should be?
Use the volumetric flow equation to determine expected D/P.
What is the main ion that cation beds remove?
lithium
What is the main ion that anion beds remove?
boron
If a temperature display fails, which sensors can be measured manually and converted to a temperature value with the help of conversion tables?
RTD and thermocouple
What is Net Positive Suction Head?
NPSH = P(suction) - P(saturation)
(in ft)
Make sure to read carefully for available vs required NPSH!
What do the four pump curves represent?
- two pumps in parallel
- change in pump speed
- two pumps in series
- a system change (valve throttled, etc.)
What is the function and use of the backseat on a manual valve?
removes pressure from the packing/stuffing box and is typically used when needed to isolate packing leakage
For proper operation of a thermocouple circuit, the reference junction temperature…
may be less than, greater then, or equal to the measuring junction temperature.
A PDP is operating in a water system. How can the net positive suction head requirement (NPSH-R) for the pump be determined?
by referencing the pump performance curve provided by the vendor, if volumetric flow rate is known
