Dynamic Thermal Ratings for Overhead Lines

1. Dynamic Thermal Ratings for Overhead Lines Philip Taylor, Irina Makhkamova, Andrea Michiorri Energy Group, School of Engineering Durham University

2. Overview • Research Overview • Overhead Line Thermal Modelling • Lumped Parameter • Computational Fluid Dynamics • Comparisons • Thermal State Estimation • Further work Energy Group School of Engineering

3. 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 Group School of Engineering

4. Project Consortium • Part funded by DIUS Energy Group School of Engineering

5. 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 Group School of Engineering

6. 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 What Do We Mean By Dynamic Thermal Ratings? • How • Exploit headroom which is available for a reasonable amount of time • Never exceed the standard component continuous operation design temperature Energy Group School of Engineering

7. Lumped Parameter Modelling of the Thermal State of OHL Conductors

8. Lumped Parameter Model – Standard comparison • IEC TR 61597 • IEEE 738 • CIGRE WG 22.12 in ELECTRA 144 – 1992 • The IEC model has been selected C B A Maximum current carrying capacity – models comparison Conductor ACSR 175mm2 LYNX Wd=90º, Ta=25 [ºC], Sr=0 [W/m2] Energy Group School of Engineering

9. Lumped Parameter Model – Simulation 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 Network diagram and line characteristics Voltage: 132kV, line length: 7km, conductor: ACSR 175mm2 LYNX Energy Group School of Engineering

10. Lumped Parameter Model – Simulation results The simulations suggest that consistent headroom is available when using daily or hourly ratings Comparison of energy transfer capacity for different rating period Minimum daily rating compared with seasonal ratings Weather data from Valley (Anglesey) Energy Group School of Engineering

11. CFD Modelling of the Thermal State of OHL Conductors

12. Outlet Conductor Inlet Air domain Modelling the thermal state of ACSR 410 conductor exposed to cross wind ASCR410: 7 steel strands surrounded by 27 aluminium strands. Simplified geometry The outer diameter is 28.5mm 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). 2-D calculation scheme Energy Group School of Engineering

13. Modelling thermal state of ACSR 410 conductor exposed to cross wind Energy Group School of Engineering

14. Modelling the thermal state of LYNX conductor exposed to cross wind Real geometry Simplified geometry Computational grid Lynx consists of 30 strands of an aluminium wire and 7 strands of a steel wire. Outer diameter is 19.5 mm Energy Group School of Engineering

15. Modelling the thermal state of Lynx conductor exposed to cross wind The ambient temperature is 293 K; I = 433A. CFD predicts 16 K headroom existence Energy Group School of Engineering

16. Impact of solar radiation on the conductor temperature Initial conditions: Cross wind = 2 m/s, Current = 433A, T ambient= 293 K • 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) Energy Group School of Engineering

17. Lynx conductor exposed to cross wind - comparison with measured data on distribution network Energy Group School of Engineering

18. CFD Model: the Lynx conductor exposed to cross wind - comparison with real data Energy Group School of Engineering

19. Lynx conductor exposed to parallel wind Temperature of the conductor vs. velocity for cross and parallel wind conditions Calculation scheme Outlet Conductor Temperature, K Inlet Air domain Conductor Aluminium Wind velocity, m/s Steel core The ambient temperature is 293 K; I = 433A Energy Group School of Engineering

20. Comparison Between CFD and Lumped Parameter Modelling of the Thermal State of OHL Conductors

21. CFD / Lumped comparisonCross wind, temperature Conductor temperature. CFD/Lumped parameter comparison Conductor: ACSR 175mm2 LYNX, Ta=20'C, I=433A, Wd=90' Energy Group School of Engineering

22. CFD / Lumped comparisonParallel wind, temperature Conductor temperature. CFD/Lumped parameter comparison Conductor: ACSR 175mm2 LYNX, Ta=20'C, I=433A, Wd=0' Energy Group School of Engineering

23. Thermal State Estimation

24. 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 Energy Group School of Engineering

25. State Estimation – Simulation results Minimum, mean and maximum hourly rating Energy Group School of Engineering

26. 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) Energy Group School of Engineering