Blackout Theory. EE8725 Apoorva Mysore Nataraja

Transcription

1 Blackout Theory EE8725 Apoorva Mysore Nataraja 1

2 Northeast Blackout of

3 Major power outages in history Blackouts People affected (millions) Location Date July 2012 India blackout 620 India July 2012 January 2001 India blackout 230 India 02-Jan Pakistan blackout 140 Pakistan 26-Jan Java Bali blackout 100 Indonesia 18-Aug Southern Brazil blackout 97 Brazil 11-Mar Brazil and Paraguay blackout 87 Brazil, Paraguay Nov Turkey blackout 70 Turkey 31-Mar-15 Northeast blackout of United States, Canada Aug

4 Series of events 1 - Aug 14, 2003 Hours before the Aug. 14 blackout, FirstEnergy were importing thousands of megawatts from southern Ohio, and exporting VAR's outside their system the whole day. Voltage across their system was below normal, a sign of insufficient reactive power. By 1:15 p.m., voltage had dropped 3 to 4 percent, close to the 5 percent threshold considered a serious problem. FirstEnergy then adjusted nine power plants to produce more reactive power, but trouble at one plant forced the generator off. At 2:02 p.m., a brush fire caused a major line in southwest Ohio to fail, redirecting power loads onto other lines, and once again increasing the need for reactive power. Then, starting at 3:05 p.m., a series of lines linking the Cleveland area to its power supplies to the south failed. At 4:09 p.m., the last links between northern and southern Ohio shut down. The system began to falter, and within two minutes, the blackout had struck

5 How blackouts happen? Lack of reactive support close to the loads to sustain adequate voltage levels Voltage collapse due to overloading Multiple contingencies, internal breakdown Weather conditions Ageing equipments Maintenance practises 5

6 Reactive effects of transmission loss: ΣI 2 l x l - Σ(V 2 B + from end of line l cap l V2 B ) - ΣV 2 B to end of line l cap l i fixed cap at bus i Reactive loss on transmission line Reactive power injected into the system from line charging capacitance Reactive injections from fixed capacitors Summing the above three terms gives the reactive power loss. When a line is lost, it leads to increased current flow in the other lines and causes bus voltages to drop, thereby increasing reactive power loss. Decreased var injections increase var demand on generators, and if they hit their var limits, generator terminal voltage drops. 6

7 Voltage collapse As more reactive power is drawn from the system, voltage drops. At the critical point, the system will have to solution. Voltage collapse occurs when the system is trying to support much more load than the voltage can support. 7

8 Case 1: All lines in service 3000 MW transfer 500 MW per line Voltage is 100% rated voltage (300 MVARs required by lines) East generator is below 1200 MVAR limit 8

9 Case 2: One line out 3000 MW transfer 600 MW per line Voltage is 100% rated voltage (362 MVARs required by lines) East generator is below 1200 MVAR limit 9

10 Case 3: Two lines out 3000 MW transfer 750 MW per line Voltage is 100% rated voltage (453 MVARs required by lines) East generator is at 1200 MVAR limit 10

11 Case 4: Three lines out 3000 MW transfer 1000 MW per line Voltage is 99% rated voltage (611 MVARs required by lines) East generator is at 1200 MVAR limit 11

12 Case 5: Four lines out 3000 MW transfer 1500 MW per line Voltage has dropped to 97% of rated voltage (957 MVARs required by lines) East generator is at 1200 MVAR limit 12

13 Case 6: System collapse This simulation could not solve the case of 3,000 MW transfer with five lines out. Numbers shown are from the model s last attempt to solve. The West generator s unlimited supply of VARs is still not sufficient to maintain the voltage at the East bus. Voltage has dropped to 77% of rated voltage 13

14 Case 7: Two lines out - Full voltage control (452 MVARs required by lines) 14

15 Case 8: Three lines out - Full voltage control (606 MVARs required by lines) 15

16 Case 9: Four lines out - Full voltage control (922 MVARs required by lines) 16

17 Case 10: Five lines out - Full voltage control (2000 MVARs required by lines) 17

18 Case 11: How much could the line have handled? 4900 MW 18

19 NERC (n-1) rule No single generation outage will result in so large a frequency drop that other generators will be forced off line. No single transmission or generation outage will result in other components experiencing such a large flow or voltage change that new limit violations occur. 19

20 How to prevent blackouts? 1. System monitoring and Audits - Run state estimation - Test power flows, voltage magnitudes against limit values - Maintain critical alarm monitoring systems 2. Contingency analysis (What if analysis) - Detect abnormal system conditions - Detect components/parameters that will be out of limit 3. Security constrained OPF 4. Public policy, Transmission and future investments - Long term investments, replacement of ageing infrastructure - Transmission grid upgradation 20

21 References Peter W. Sauer, Reactıve Power and Voltage Control, NSF Workshop on applied mathematics for deregulated power systems, Nov 3-4, 2003, Alexandria, VA. Damir Novosel, Energy pulse article net/centers/article/article_print.cfm?a_id=495 Bruce F. Wollenberg, Power System Securıty - Lecture 11A youtube.com/watch?v=hogllqfj3m0 21

22 Thank you 22