Dynamic Thermal Ratings for Overhead Lines Philip Taylor, Irina Makhkamova, Andrea Michiorri Energy...
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Transcript of Dynamic Thermal Ratings for Overhead Lines Philip Taylor, Irina Makhkamova, Andrea Michiorri Energy...
Dynamic Thermal Ratings for Overhead Lines
Philip Taylor, Irina Makhkamova, Andrea Michiorri Energy Group, School of Engineering
Durham University
Energy GroupSchool of Engineering
Overview• Research Overview• Overhead Line Thermal Modelling
– Lumped Parameter– Computational Fluid Dynamics– Comparisons
• Thermal State Estimation• Further work
Energy GroupSchool of Engineering
Research Aims• The use of dynamic thermal ratings to:
– Increase utilisation of existing power system assets.
– Facilitate increased capacities and energy yields for DG
– Develop a real time controller
Energy GroupSchool of Engineering
Project Consortium
• Part funded by DIUS
Energy GroupSchool of Engineering
Project Phases
• Thermal Modelling (OHL, UGC and TFMR)• Thermal State Estimation• DG constrained connection techniques• System Simulation• Network and Meteorological
Instrumentation• Open Loop Trials• Closed Loop Trials
Energy GroupSchool of Engineering
What Do We Mean By Dynamic Thermal Ratings? Aim
To increase the energy transferred through the network under normal operating conditions
Without reducing component lifetime or network security
Measurements Availability of a limited
number of environmental measurements
Electrical measurements available from SCADA
How Exploit headroom which is available for a reasonable amount of time Never exceed the standard component continuous operation design
temperature
Lumped Parameter Modelling
of the Thermal State of OHL Conductors
Energy GroupSchool of Engineering
Lumped Parameter Model – Standard comparison
IEC TR 61597 IEEE 738CIGRE WG 22.12 in ELECTRA 144 – 1992
The IEC model has been selected
0
400
800
1200
0 2 4 6 8 10 12v [m/s]
I [A
] IEEE
IEC
CIGRE'
Maximum current carrying capacity – models comparison
Conductor ACSR 175mm2 LYNX
Wd=90º, Ta=25 [ºC], Sr=0 [W/m2]
A
B
C
Energy GroupSchool of Engineering
Lumped Parameter Model – Simulation
33kV
132kV
132kV
400kV
132kV
33kV
Local load
Local loadLocal
Generator
Network diagram and line characteristics
Voltage: 132kV, line length: 7km, conductor: ACSR 175mm2 LYNX
Town A
Town B
The network and its geographical location
Costal area, west coast, subject to sea breeze
Three directions for the line, the smallest rating has to be considered
Energy GroupSchool of Engineering
Lumped Parameter Model – Simulation results
GWh/year
Yearly (summer) rating
762
Seasonal ratings 879
Daily ratings 1393
Hourly ratings 16960
200
400
600
800
1000
1200
1400
Jan
Mar
May
Jun
Aug
Oct
Dec
Time [months]
Rat
ing
[A].
Seasonal
Daily
Minimum daily rating compared with seasonal ratings
Weather data from Valley (Anglesey)
Comparison of energy transfer capacity for different rating period
The simulations suggest that consistent headroom is available when using daily or hourly ratings
CFD Modelling of the Thermal State of OHL
Conductors
Energy GroupSchool of Engineering
Modelling the thermal state of ACSR 410 conductor exposed to cross wind
The outer diameter is 28.5mm
ASCR410: 7 steel strands surrounded by 27 aluminium strands.
Simplified geometry
M. Isozaki and N. Iwama. Verification of forced convective cooling from conductors in breeze wind by wind tunnel testing. (0-7803-7525-4/02, 2002 IEEE).
Outlet Conductor Inlet
Air domain
2-D calculation scheme
Energy GroupSchool of Engineering
Modelling thermal state of ACSR 410 conductor exposed to cross wind
0
20
40
60
80
100
120
140
160
180
200
220
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Wind velocity, m/s
Tem
per
atu
re r
ise,
K Published data
Empirical data (text book)
CFD data
Energy GroupSchool of Engineering
Modelling the thermal state of LYNX conductor exposed to cross wind
Lynx consists of 30 strands of an aluminium wire and 7 strands of a steel wire.
Outer diameter is 19.5 mm
Real geometry Simplified geometry Computational grid
Energy GroupSchool of Engineering
Modelling the thermal state of Lynx conductor exposed to cross wind
292
294
296
298
300
302
304
306
308
310
312
314
316
318
320
322
324
326
328
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Wind velocity,m/s
Tem
per
atu
re i
n t
he
con
du
cto
r, K
2-D model
3-D model
Design core temperature (ER P27)
The ambient temperature is 293 K; I = 433A.
CFD predicts 16 K headroom existence
Energy GroupSchool of Engineering
Impact of solar radiation on the conductor temperature
•Additional source of heat emanates from solar radiation
•q = α · d · s •α = solar absorption coefficient, this • varies from 0.3 to 0.9•d = diameter of conductor (m)•s = intensity of solar radiation (W/m2), • a typical value being 800 (W/m2)
20
27.37 27.7829.6 30.9
33.3
0
5
10
15
20
25
30
35
Te
mp
era
ture
, d
egre
es
C
1 2 3 4 5 6
Temperature in the Lynx conductor
1 Ambient temperature
2 Temperature of the conductor taking into account convection and radiation losses
3 Temperature of the conductor taking into account convection and radiation losses and temperature – dependent resistivity
4, 5, 6 Temperature of the conductor taking into account convection and radiation losses, temperature – dependent resistivity and solar radiation with insolation of 240W/m2, 400 W/m2, and 720 W/m2, respectively.
Initial conditions: Cross wind = 2 m/s, Current = 433A, T ambient = 293 K
Energy GroupSchool of Engineering
Lynx conductor exposed to cross wind - comparison with measured data on distribution
network
DateTim
eAmbient Temperat
ure(deg. C)
Wind
Speed(m/s)
Windspeed Avg
(m/s)
Wind Directio
n(deg.)
Solar Radiati
on(W/m2)
Line
temperature
(deg C)
I (A)
Case 1:
27/03/2008 12:50 8.4 (0.4) 1.3 189 232 15.5 30.59
Case 2:
27/03/200820:15 7.6 (2.2) 3.5 86 0 10.0 83.13
Energy GroupSchool of Engineering
CFD Model: the Lynx conductor exposed to cross wind - comparison with real data
Case 1
Case 2
280
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282
283
284
285
286
287
288
289
290
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16Wind velocity, m/s
Tem
per
atu
re,
K
data (deg C) CFD (deg C) Difference (deg C)
Case 1 15.5 9.9 5.6
Case 2 10.0 7.8 2.2
Energy GroupSchool of Engineering
Lynx conductor exposed to parallel wind
The ambient temperature is 293 K; I = 433A
Calculation scheme
ConductorOutlet
Inlet Air domain
290
300
310
320
330
340
350
360
0 2 4 6 8 10 12 14 16
Te
mp
era
ture
, K
Cross wind
Parallel wind
Temperature of the conductor vs. velocity for cross and parallel wind conditions
Wind velocity, m/s
Tem
pera
ture
, K
Aluminium
Steel core
Conductor
Comparison Between CFD and Lumped Parameter
Modelling of the Thermal State of OHL
Conductors
Energy GroupSchool of Engineering
CFD / Lumped comparisonCross wind, temperature
295
300
305
310
315
320
325
0 1 2 3 4 5
Ws [m/s]
Tc
[K]
T [K] Lumped
T [K] CFD
Conductor temperature. CFD/Lumped parameter comparison
Conductor: ACSR 175mm2 LYNX, Ta=20'C, I=433A, Wd=90'
Energy GroupSchool of Engineering
CFD / Lumped comparisonParallel wind, temperature
Conductor temperature. CFD/Lumped parameter comparison
Conductor: ACSR 175mm2 LYNX, Ta=20'C, I=433A, Wd=0'
300
310
320
330
340
350
360
0 1 2 3 4 5
Ws [m/s]
Tc
[K]
T [K] Lumped
T [K] CFD
Thermal State Estimation
Energy GroupSchool of Engineering
State Estimation - Objectives Produce reliable estimates of maximum current carrying capacity of power system components Identify minimum and most probable value Possibility to calculate a rating for a given probability/risk P
DF
min maxmode
variance
1
CD
F
min max
average
P
Rating
Energy GroupSchool of Engineering
0
50
100
150
200
250
00 02 04 06 08 10 12 14 16 18 20 22 00
Time [h]
Rat
ing
[MV
A]
min
mean
max
Static
State Estimation – Simulation results
Minimum, mean and maximum hourly rating
Energy GroupSchool of Engineering
Conclusions
• Encouraging results regarding potential headroom
• Lumped parameter models more conservative than CFD
• Initial comparisons to real data encouraging• Need to further validate models with real data• Need to validate state estimation with real data• Site installation• Trials (open and closed loop)