1 / 22

345kV Lines

345kV Lines. C ompetitive R enewable E nergy Z ones. Protection & Control Issues -. NERC Press Release on April 24, 2009.

nigel-west
Download Presentation

345kV Lines

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 345kV Lines Competitive Renewable Energy Zones Protection & Control Issues -

  2. NERC Press Release on April 24, 2009 “ Misoperations of system protection and control systems have been a leading cause of bulk power system disturbance in North America for a number of years, causing nearly 45% of category two and higher disturbances in 2007 ” -NERC

  3. NERC Statistics

  4. NERC Standards, Papers, Reports etc. • PRC-001-01: System Protection Coordination • PRC-004-01: Analysis and Mitigation of T and G Protection System • Reliability Paper: Protection System Reliability - Redundancy • Special Report: Accommodating High Levels of Variable Generation • And more …..

  5. Can backup protection trip within 18 cycles ? Can breaker failure prot. trip within 9 cycles ? Wind farm LVRT curve from FERC 661A and PRC-024-1 0.65pu 18 cycles 0.45pu 9 cycles

  6. Which should be used for CREZ lines ? Transmission Line High-Speed Protection High-Speed Line Protection: Communication-based protection scheme that can cover 100% line and trip in 1-2 cycles • Power line carrier-based schemes - DCB or POTT • Optical fiber-based current differential scheme (87L)

  7. Z1 Z2/3 Z2/3 Z1 Power Line Carrier (PLC) - Based Schemes • Utilizing power line for communication. Consist of wave traps, coupling capacitors, line tuners, transmitters, receivers, etc. • Two prevailing PLC-based schemes: • Directional Comparison Blocking Scheme (DCB) • Permissive Overreach Transfer Trip (POTT) • Dependent upon distance (21)and directional (67) elements 21 21 PLC Channel

  8. I_Local I_Remote Line Differential Protection (87L) • Based on digital communication channels such as optical fibers, SONET network, etc. • Compare current flow in & out line terminals • Easy to discriminate internal & external faults • High dependability – instantaneous trip for all internal faults • High security – no operation for external faults 87L 87L

  9. PLC Schemes vs. 87L : Mutually Coupled Lines • Many CREZ 345kV lines are double circuits in long distance • Zero sequence mutual coupling effects 21G / 67G • 21G may overreach or underreach • Wrong direction from 67G due to zero seq. voltage reversal • Mis-operations occur often from DCB or POTT due to communication errors • 87L is not affected by mutual coupling

  10. PLC Schemes vs. 87L: Current Reversal • Cause: one end tripped prior to the other end • 21 / 67 may give wrong directions • DCB or POTT may trip the healthy line due to scheme error • 87L is not affected by current reversal

  11. PLC Schemes vs. 87L: Power Swings • Power system dynamic balance is disturbed after loss of critical generators or transmission lines • Swings could be damped by automatic & manual system controls, or aggravated towards out-of-step and blackout • 21P is susceptible to power swings • 87L is not affected by power swings

  12. PLC Schemes vs. 87L: CCVT Transients • 21 and 67 protection are relying on voltage signals • CCVT transients may cause overreach, underreach, delayed trip or wrong direction • DCB or POTT may mis-operate for wrong direction • 87L is not affected by CCVT transients at all

  13. RF ZSC&MOV ZAPPARENT PLC Schemes vs. 87L: Series-compensated Line • Protection Issues brought by series-compensation (SC) • Uncertainties caused by SC, MOV and bypass switch • Voltage inversion and current inversion effect 21/67 • 21 over-reach or under-reach • Sub-synchronous resonance effects phasor measurement • Other interactions with system components • DCB or POTT schemes have high probability of mis-operation for SC line and the adjacent linesas well • 87L is immune to all above issues except current inversion, that can be overcome by proper 87L settings K*Z0L (1-K)*Z0L remote bus X I0 Z0S2 Z0S1 V0 R A zero seq. network example

  14. PLC Schemes vs. 87L: Weak Feed Applications • Wind farm is regarded as weak source or no source • 21/67 at weak terminal may not see the fault • DCB and POTT need special logics to handle weak feed applications, at a price of increasing the complexity of coordination and increasing possibility of mis-operation • Weak feed has no impact on 87L

  15. PLC Schemes vs. 87L: High Impedance Faults • 21G cannot detect ground faults with high impedance • 67G has to compromisebetween the sensitivity and security against system unbalance under heavy load • 87L is sensitive to internal high impedance faults and not affected by load

  16. PLC Schemes vs. 87L:Cross Country Faults, Evolving Faults • Cross Country Faults: two faults at the same time but different locations, one internal and one external • Evolving Faults: 1LG fault evolves to 2LG or 3LG fault • 21 or 67 could be confused, DCB or POTT may mis-trip for external fault or no-trip for internal fault • 87L can discriminate if there is internal fault, and not confused by evolving faults

  17. Summary on PLC-based schemes vs. Fiber-based 87L

  18. Proposed 345kV Line Protection Schemes for CREZ Redundant protection system including: • Dual high speed primary protections • Redundant communication channels using optical fibers fibers fibers Self-healing SONET MUX MUX 87L 87L Direct fibers 87L 87L • Primary A: Line differential protection (87L) over direct fibers • Primary B: 87L over self-healing SONET network

  19. OPGW for Every New CREZ 345kV Line • Optical Fiber Composite Overhead Ground Wire (OPGW) • Lower cost for new line construction • Expensive to put in afterwards (factor of 5-7) • Other benefits of optical fiber network utilizing OPGW • Wide Area Control • Synchronous phasor data stream • SCADA network communication • Disturbance monitoring system • Video surveillance system • Smart grid, voice communicationetc.

  20. Breaker Failure Protection • Since over 20% generation may be from wind / sun, system stability has high requirements on backup protection • Wind farm LVRT curve implies fault clearance within 9 cycles even if breaker fails BF trip 86 trip DTT trip Fault cleared Fault Inception Breaker clearing Fault detector Local & remote Safety Margin Relay time breakers clearing time time drop out time t (cycles) General Total 13-14 2 3 1-2 2 5 Better breakers 1 2 < 1 2 3 Total 8-9 & better schemes

  21. Summary • Redundancy is necessary for CREZ 345kV lines • 87L is superior to carrier-based schemes • Communication channels using optical fibers and self-healing SONET network • OPGW for every new CREZ 345kV line • Breaker failure and backup timing • Joint Development of CREZ Common approach / design specification on system protection and control

  22. Discussion Questions? Comments?

More Related