Some thoughts on. The Future of Electric Power Transmission

Transcription

1 Some thoughts on. The Future of Electric Power Transmission

2 Enhaing Capacity of today s Systems: Improve Capacity thru 1. Better using intrinsic characteristics of transmission lines 2. Adding equipment to achieve greater flows Series compensation Reactive power sources Phase angle shift Ireasingly dependent on power electronics. FACTS

3 Current-activated Tension Adjuster

4 Distributed Reactive Drop Compensation Series quadrature voltage adjuster:

5 Enhaing Capacity of todays System: Improve Capacity thru 1. Better using inherent characteristics of transmission lines 2. Adding equipment to achieve greater flows Series compensation Reactive power sources Phase angle shift Ireasingly dependent on power electronics. FACTS

6 How many MW/ft 2? ft 2 10

7 imod Poynting Vector Analysis 25 S = ExH S max = E 2 max Z i E max = 30 kv cm MW S = m max = 12,000 1, P = 278, 810MW 250 ft 2 MW ft 2 10

8 How are we doing? 138 kv ~ 200 MW (0.08%)

9 High Phase Order Transmission 3 phase 6 phase 12 phase Infinite phase order insulating conducting

10 It Works.but imagine the substation! 3 phase 6 phase 12 phase

11 1. ACCR

12 Potential for Current & Voltage Uprating Reconductoring allows: 1. Current uprating by reducing sag 2. Voltage uprating by creating extra clearae and room for more insulators. (Light weight allows bundling)

13 2. High Surge Impedae Loading Construction X reduced C ireased Voltage SIL (MW) (kv) Normal HSIL ,000 1,000-2,000

14 MOD 3. HVDC Conversion Advantages: 1. Full time-utilization of insulation 2. DC Operating advantages Obstacles: 1. High cost per iremental kw 2. Bi-pole system leaves 1/3 of a valuable line investment idle

15 MOD 3. Tri-pole HVDC An extra conductor.. Why not an extra bridge? AC AC AC A A A B 1-pole B 1-pole B C Converter Converter C C 1-pole Converter DC 1 2 3

16 Symmetrical Bi-Pole Asymmetrical HVDC Modulation modulation options Pole Pole Conductor 3 Conductor 3 is idle except in emergeies

17 Symmetrical Current- Asymmetrical Modulation Modulated modulation HVDC options One pole reversible, in current & voltage: Pole Pole Pole Pole 3 alternately relieves current from pole 2 then pole 1

18 Symmetrical Asymmetrical Modulation Modulation modulation options One reversible pole: Pole The 1 tri-pole system: 2. Reduces losses, for the same power, by 20% Pole 2 3. Can loose any conductor or pole, act like a bi-pole, and still transmit 73% of its maximum power. Pole Carries 37% more power than a bi-pole on the same 3-conductor system. 4. Needs no ground return Pole 3 alternately relieves current from pole 2 then pole 1

19 Symmetrical Current- Asymmetrical Modulation Modulated modulation HVDC options Pole Pole Pole

20 Symmetrical Transitional Modulation Ramps ramps options Ramp holds constant DC Power 1.0 I I I Modulating Pole regulated to hold neutral current to zero 4 o of a 6 minute period = 4 seconds

21 Symmetrical Transitional Modulation Ramps ramps options Constant-polarity currents overlap. providing time to reverse modulating pole polarity I 1 I 2 I 3 T (Detailed control simulation demonstrated by Dennis Woodford)

22 Symmetrical Transitional Modulation Ramps ramps options Simulation (By Dennis Woodford) of the transition with example control logic: Power (MW) Pole 1 Power (MW) Pole 3 Power (MW) Pole 2 Total Tri-pole power (MW)

23 Symmetrical Economics Transitional Modulation - AC ramps Conversion options Issues: 1. Tri-pole terminals are 10% to 20% more expensive per kw 2. This premium is offset by higher DC/AC power ratio lower cost per iremental kw 3. Tri-pole makes 37% better use of prior transmission line investment 4. Tri-pole losses are lower 5. Tri-pole has 50% higher redunday.

24 Symmetrical A 500 kv Modulation conversion Conversion options example Example Different ways to bring loading up to thermal capacity 350 oss / Mile / Phase = kw Conductor Thermal Limit 385 kv Tri-Pole 436 kv Bi-pole 500 kv AC 436 kv Tri-Pole L Power Transfer = MW

25 Symmetrical The Transmission case for Modulation promoting line promotion options 230 kv St. Clair Curve for 500 kv and 230 kv: 5,000 4,500 4,000 Loading - MW 3,500 3,000 2,500 2,000 1,500 1, kv 230 kv Miles

26 Symmetrical 230 Transmission kv Promotion Modulation line promotion options Convert the 230 to tri-pole HVDC, feed terminals from the 500 kv Bus (If the 230 kv can be spared from its own network) 1,400 Loading - MW 1,200 1, kv Tri-pole HVDC 2000 a. 230 kv AC 500 kv AC Miles

27 Symmetrical What The case about Modulation for new new HVDC tri-pole options circuits? lines MCM/2 MCM /////\\\\\/////\\\\\/////\\\\\/////\\\\\/////\\\\\/////\\\\\ /////\\\\\/////\\\\\/////\\\\\/////\\\\\/////\\\\\/////\\\\\ /////\\\\\/////\\\\\/////\\\\\/////\\\\\/////\\\ Bi-pole w Ground Return MW = 1.00 R =.5 Tri-pole without Ground Return MW = 1.37 R =.78 All towers have approximately equal wind & weight loading.approximately the same cost in $/mile

28 Symmetrical HVDC The case options Modulation for new all tri-pole equal options MW lines 100% 90% imod 80% 4 Pole + G Redunday 70% 60% 50% 40% 30% 3 Pole 3 Pole + G 4 Pole 2 Pole + G Weight Loading Wind Loading Average of Weight & Wind Loading All cases are relative to the 2-pole case without ground return. All options suspended from a single tower. 20% All Cases represent the same MW rating 10% 2 Pole 3 Phase AC 0% Tower Cost Index

29 Symmetrical Key Colusion technical Modulation / economic options issues It s worthwhile reviewing the basics of conductor configuration and use e.g. bundled circuits DC will play a bigger role in future systems. Tri-pole appears to have cost and reliability advantages both for conversion and for new lines where metallic ground return is used. Higher voltage bi-directional valves are needed both multi-terminal and tri-pole applications. Reliability criteria need to better accommodate internal circuit redunday.