Joe Coffey - TSDOS Joseph Coffey 3.pdf · Line Rating Sensitivity Comparison. Series2. Series3....
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Joe Coffey Director of Overhead Transmission General Cable/Prysmian Group High Temperature Conductor Rating Considerations
Transcript of Joe Coffey - TSDOS Joseph Coffey 3.pdf · Line Rating Sensitivity Comparison. Series2. Series3....
SEPTEMBER 5 - 7, 2018
Joe CoffeyDirector of Overhead Transmission
General Cable/Prysmian Group
High Temperature Conductor Rating Considerations
SEPTEMBER 5 - 7, 2018
IEEE Standard 738 Heat Balance Equation
Emitted Thermal Radiation
Convection cooling
I2R losses
SolarAbsorption
Presenter
Presentation Notes
heat going in on right side of equation= heat going in on left side of equation Convection, Radiation heat out, solar and I2R losses in
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Scenarios for current/temperature relationship
1590.0 kcmil 54/19 Falcon/ACSS
IEEE 738 equations show ampacity= 2449 Amps
60 Hz Ambient Temperature: 35 °C0.5 Crosswind Velocity: 2.00 ft/s0.5 Wind Angle: 90 °
98.4 W/ft² Northern Latitude: 32 °90 ° (E-W) Elevation: 774 ft
Atmosphere: clear Month and Day of Year: July 1Maximum Operating Temp 200 °C Time of Day: 12 PM
Azimuth of Line:Total Solar Radiated Heat:
Frequency:Emissivity:
Absorptivity:
20-49 °C20-49 °C20-49 °C0-6 ft/s 20-49 °C0.24-0.9
20-49 °C0.0-1.0
20-49 °C200°C (392°F)
20-4???
Presenter
Presentation Notes
Lots of utilities have summer/winter ratings. 49C (120F) hottest ever recorded in Texas Wind: Utilities here that use values from 2-6, maybe higher, risk is that drops to zero
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23592418
24802539
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49°C 40°C 30°C 20°C
Sensitivity29°C (52°F) changeequals 7.6% change in ampacity ratingWorst Case:Winter rating (20°C) used when actual Temp=49°CTemp Conductor=225°C actual vs. 200°C expected
Ambient Temperature: vary from 49°C (120°F) to 20°C (68°F)
Ampacity Rating @ 200°C vs. Ambient Temp
Ampa
city
Ambient Temperature
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2169
2449
2776
3043
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0 ft/s 2 ft/s 4 ft/s 6 ft/s
Ampa
city
Wind Speed
Ampacity Rating @ 200°C vs. Wind Speed Sensitivity0 to 2ft/s = +12.9% 0 to 4ft/s = +27.9%0 to 6ft/s = +40.3%
Worst Case: Wind stops blowing for period of time on line rated @6ft/sTemp Conductor=340°C actual vs. 200°C expected
Cross Wind Velocity: vary from 0 ft/s to 6 ft/s
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2384 24172481 2513
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1 0.75 0.25 0
Sensitivity100% change in valueequals 5.4% change in ampacity ratingWorst Case: Assume no sun absorbed when actual α =1.0Temp Conductor=218°C actual vs.200°C expected
Absorptivity (α ): vary values from 1.0 to 0.0
Ampacity Rating @ 200°C vs. Absorptivity
Ampa
city
Absorptivity
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Sensitivity0.66 change in valueequals 26.1% change in ampacity rating
Worst Case: “shiny” new line rated with Ɛ=0.9 Temp Conductor=326°C actualvs. 200°C expected
Emissivity (Ɛ): vary from 0.24 to 0.9
2205
2449
2621
2781
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0.24 0.5 0.7 0.9
Ampa
city
Emissivity
Ampacity Rating @ 200°C vs. Emissivity
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Absorptivity Temperature Emissivity Wind speed
Ampa
city
Rat
ing
Ampacity Rating Sensitivity @ 200°C
1.0
Nig
ht T
ime
0.9
0.24
20°C
49°C
0 ft
/s
6ft
/s
Impact from wind speed and emissivity much greater than ambient temp and absorptivity
Summary of impact of variables
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Summary of impact of variables at 90°C vs. 200°C
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1000Ad
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Ampa
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cha
nge
Line Rating Sensitivity Comparison
Series2
Series3
Absorptivity:Reduce from
1 to 0
Emissivity:Increase from
0.24 to 0.9
Ambient Temp:Reduce from 49°C to 20°C
Wind Speed:Increase from 0ft/s to 6 f/s
@90°C
@200°C
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EPRI test results from Texas. What value to use?Age
(Years)Measured Emissivity Location Conductor
0 0.24 - ACSR-Drake3 0.25 Amarillo ACSS-Falcon
32 0.32 DFW ACSR-Bittern32 0.45 Austin ACSR-Drake
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Lower Pollution equals lower emissivity
S02N0X
SuspendedParticulates
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For HTLS Conductors, Emissivity Matters.
Peak Temp = 187°C
Peak Temp = 265°C
Emissivity = 0.9
Emissivity = 0.24
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If actual Ɛ =0.3/α =0.3, what would conductor temp be with commonly used rating methodology Ɛ/α value sets?
200 215 229254
274 286
0
50
100
150
200
250
300
350
0.3/0.3 0.4/0.4 0.5/0.5 0.7/0.9 0.8/0.8 0.9/1
°C
Emissivity/Absorptivity
Calculated Conductor Temperature
2292
A
2372
A
2449
A
2573
A
2667
A
2724
A
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Line Rating observations for High Temperature Lines• Emissivity and Wind Speed are major contributors• Emissivity is measurable • Actual emissivity values are likely lower than
commonly used values• HTLS conductor ratings are particularly sensitive to
emissivity changes. • Consistency of line rating “philosophy” should be
reevaluated for HTLS conductors vs. traditional ACSR
