ptresentación ieee std 738
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8/20/2019 Ptresentación IEEE Std 738
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Improving Overhead TransmissionLine Usage Efficiency on a
Caribbean Island Power System
S. Bahadoorsingh, L. Bhairosingh, S. Sharma, M. Ganness
The University of the West Indies | Dept of Electrical and Computer Engineering
IEEE PES T&D 2014
Chicago, Illinois
16th April 2014
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Transmission Line Rating Factors
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Dynamic Line Rating – The Concept
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• Know true line capacity in real time
• Improve system reliability
• Optimize grid utilization
(Oncor Electric Delivery Company, 2010)
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Standards
1. IEEE Standard for Calculating the Current-
Temperature of Bare Overhead Conductors
(IEEE 738-2006)
2. Cigré “Thermal Behaviour of Overhead
Conductors”
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Heat Balance Equation (IEEE 738)
2 ( )r c s cq q q I R T
Heat losses Heat gains
Radiated heat loss
Convected heat loss
Solar heat gain
Joule heating
( )
r c s
c
q q q I
R T
Ampacity
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Screenshot of developed MATLAB based DLR software showcasing the steady state calculation window.
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T&TEC Case study
Chaguanas East- Chaguanas West Circuit
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Conductor type: Wolf
Conductor
diameter (mm)
AC resistance
@ 25°C (Ωm-1)
AC resistance
@ 75°C (Ωm-1)
18.1 0.000183 0.000223
Manufacturer Rating (temperate climate): 512 A
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Hourly readings for wind speed based on ARMA model and ambient temperature and for July 18th 2012
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Actual conductor loading for July 18th 2012 and calculated ampacity
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Results:
o Highest ampacity calculated was 107% greater than manufacturer’s
rating and 197% higher than actual conductor loading
o Lowest ampacity calculated was 42% higher than manufacturer’s rating
and 103% higher than actual conductor rating
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Constraints/ Limitations
• Lack of real time updating of climatic data
• More loading data needed for lines with climatic data available
Further Work
• Effects of DLR on:
o system voltages and losses
o unit commitment
o contingency planning
o protection circuitry
•Cost analysis
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Conclusion• Electricity transmission traditionally limited by line’s thermal limit
• Static ratings challenged as being overly conservative due to load growth
• DLR provides improved asset management
• T&TEC case study:
o Highest ampacity calculated was 107% greater than manufacturer’s
rating and 197% higher than actual conductor loading
o Lowest ampacity calculated was 42% higher than manufacturer’s rating
and 103% higher than actual conductor rating
• DLR provides progression to a smarter grid
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ReferencesBernini, Minardo, Persiano, A. Vaccaro, D. Villacci and L. Zeni. 2007. “Dynamic
loading of overhead lines by adaptive learning techniques and distributedtemperature sensing.” IET Generation, Transmission and Distribution 1 (6):
912-919
Ciniglio, Orlando A., and Anjan Deb. 2004. “Optimizing Transmission Path
Utilization in Idaho Power.” IEE Transactions on Power Delivery 19 (2): 830-
834.Hall, J.F., and A.K.Deb. 1988. “Economic Evaluation of Dynamic Line Rating by
Adaptative Forecasting.” IEE Transactions on Power Delivery 3 (4): 2048-
2055.
Kopsidas, Konstantinos. 2009. "Modelling Thermal Rating of Arbitrary
Overhead Line System." Doctoral Thesis. The University of Manchester,United Kingdom.
Kopsidas, K., and S. M. Rowland. 2011. “Evaluating opportunities for
increasing power capacity of existing overhead line systems.” IET
Generation, Transmission and Distribution 5 (1): 1-10.
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Appendix
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Heat loss- radiation (IEEE 738)
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4 4273 273
0.0178 -
100 100
[ ]r Tc Ta
q D
Conductor temperature Ambient temperature
Conductor diameter Emissivity
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Heat loss - convection (IEEE 738)
• Wind speed = 0ms-1 (natural convection occurs)
• Wind speed < 0.6096ms-1
• Wind speed > 0.6096ms-1
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0.52
1 1.01 0.0372 ( )[ ] f w
c f angle c a
f
D V q k K T T
0.6
2 0.0119 ( )[ ] f w
c f angle c a
f
D V q k K T T
0.5 0.750.0205 ( )cn f c aq D T T
Air density
Wind speed
Air viscosity
Thermal conductivity of air Wind direction factor
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Heat Gain (IEEE 738)
• Solar heating
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'
sin( ) s seq Q A
Absorption coefficient
Total solar and sky radiated heat flux rate
Angle of incidence of sun's rays
Conductor area per unit length
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Heat Gain (IEEE 738)
• Joule heating
• AC resistance
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2 ( )c I R T
( ) ( )( ) [ ]( ) ( )high low
c c low low
high low
R T R T T T
R T T T R T
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Non-steady state (IEEE 738)
Fault: Less than 5 minutes
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2c p
dT mC I R
dt
Total conductor heat capacity
Change in conductor temperature
No heat exchange between the conductor and its environment.
Ambient temperature has no effect on the conductor’s temperature.
If line were operating below maximum allowable temperature before fault, the
heat storage capacity of the conductor allows it to tolerate a higher amount of
current for the duration of the fault.
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Non-steady state (IEEE 738)
Non-steady state: Between 5-30 minutes
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2( )c
c r p c s
dT q q mC I R T q
dt
Immediately prior to stepchange (t=0-)
• Conductor is in thermal
equilibrium
•
Heat gains = heat losses
Immediately following stepchange (t=0+)
• Conductor resistance,
temperature, heat losses
(qr, qc)remain unchanged
• Rate of generation of ohmic
losses increase
• Conductor temperature
begins to increase
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(IEEE 738, 2006)