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Distance Protection Various Reach Schemes.ppt
- 4. Zone 1 set to 80% leaves 2 end zones Faults in end zone results in instantaneous tripping at one end and time delayed at the other Time delay may lead to system stability problems Sequential clearance leaves no dead time for high speed A/R cycle (transient fault becomes permanent) Longer clearance times - More damage Basic Distance Scheme - Disadvantages
- 5. Z3 Z3 Z1X Z1X Z2 Z2 Z3 Z2 Z1 1 . T2 T3 Trip & 1 Z1X A/R Z3 Z2 Z1 1 . T2 T3 Trip & 1 Z1X A/R Z1 Z1 Zone 1 Extension Scheme
- 6. No signalling channel required (may be used as temporary replacement for carrier aided scheme when comms. channel out of service) Provides fast fault clearance at both ends for a transient fault anywhere along the line length Allows the use of high speed A/R cycle Zone 1 Extension - Advantages
- 7. Tripping can occur for external faults (but will be followed by an autoreclose) Basic distance scheme logic applies following reclose (i.e. potential for time delayed clearance for permanent faults) Only suitable to systems where autoreclose is used (for example can not be used on cable circuits) Zone 1 Extension Scheme - Disadvantages
- 8. Loss of Load Accelerated Trip Z3 Z3 Z1 Z1 Z2 Z2 Z2 .. & .. . Trip & & . 1 . LDA LDB LDC 0 T2 T1 0 T1 = 40ms (allows for slowest pickup of Zone 2) T2 = 18ms (prevents LOL trip for external fault with CB pole scatter)
- 9. Fast fault clearance without the need for a signalling channel Only applicable where 3 phase tripping is used Only operates for unbalanced faults Load current (above the current detector settings) must exist prior to the fault to ‘arm’ the scheme Can be used as back up to signal aided scheme Loss of Load Scheme
- 11. Provide high speed clearance for all faults on line (for example current differential) Do not provide inherent back-up protection SOLUTION IS TO PROVIDE DISTANCE PROTECTION FOR BACK- UP PROTECTION OF ADJACENT LINES WITH AN AIDED TRIPPING SCHEME FOR HIGH SPEED PROTECTION OF WHOLE LINE Requires the use of an ON/OFF signalling channel between line ends (i.e. HF/VF/Fibre Optic/Radio) Unit Protection Schemes
- 12. Acceleration Transfer tripping – Direct – Permissive Underreach – Permissive Overreach Blocking Types of Aided Tripping Schemes
- 13. Z3 Z3 Z1 Z1 Z2 Z2 Z3 Z2 Z1 1 . T2 T3 Trip Z3 Z2 Z1 1 . T2 T3 Trip Tx Rx Tx Rx Send Logic : Z1 Trip Logic : Rx Direct Transfer Trip
- 14. All faults anywhere along the protected line can be cleared instantaneously at both line ends Scheme can be advantageous for protecting 3 terminal lines due to ease of application Direct Transfer Trip - Advantages
- 15. A very secure signalling channel is required :- incorrect operation leads to false tripping Circuit breakers at both line ends must be closed and contribute fault current to obtain high speed fault clearance If the channel fails only the Basic scheme logic will be provided Direct Transfer Trip - Disadvantages
- 16. Z3 Z3 Z1 Z1 Z2 Z2 Change Z1 reach Z3 Z1/Z2 1 . T2 Trip T3 Z3 Z1/Z2 1 . T3 T2 Trip Tx Rx Tx Rx 1 . 1 . Send Logic : Z1 Trip Logic : Rx + Z2 Acceleration Scheme (for Reach Stepped Relay)
- 18. Z3 Z3 Z1 Z1 Z2 Z2 Tx Rx Tx Rx Send Logic : Z1 Trip Logic : Rx + Z2 Z3 Z2 Z1 1 . T2 T3 Trip T2 & Z3 Z2 Z1 1 . T2 T3 Trip T2 & 100 0 100 0 Permissive Underreach Scheme
- 19. A 21 C B D A C B D Send Fault Fault Race between relay at D picking up and signal send from relay at C resetting, following opening of breaker at C If signal send from C resets before relay D operates then aided tripping will not occur To prevent this a 100ms delay on drop off of the signal send is used in the scheme logic 21 21 21 Permissive Underreach Scheme Rx + Z2 Rx + Z2
- 20. Only a simplex signalling channel required Scheme is very secure as signalling channel only keyed for internal fault (Zone 1 initiation) Permissive Underreach Transfer Trip - Advantages
- 21. If one terminal of the line is open then only Basic scheme logic will apply If there is a weak infeed at one terminal then only Basic scheme logic will apply If signalling channel fails then only Basic scheme logic will apply Resistive coverage is governed by Zone 1 setting (may be limited on short lines) Permissive Underreach Transfer Trip - Disadvantages
- 22. Z3 Z2 Z1 1 . T2 T3 Trip & T2 Z3 Z2 Z1 1 . T2 T3 Trip & T2 Rx Tx Rx Tx Z3 Z3 Z1 Z1 Z2 Z2 Send Logic : Z2 Trip Logic : Rx + Z2 Permissive Overreach Scheme Internal Fault
- 23. Z3 Z2 Z1 1 . T2 T3 Trip & T2 Z3 Z2 Z1 1 . T2 T3 Trip & T2 Rx Tx Rx Tx Z3 Z3 Z1 Z1 Z2 Z2 Send Logic : Z2 Trip Logic : Rx + Z2 Permissive Overreach Scheme External Fault
- 24. Z3 Z2 Z1 T2 T3 Trip & T2 Z3 Z2 Z1 T2 T3 Trip & T2 & 1 Rx Tx CB open & 1 Rx Tx CB open Z3 Z3 Z1 Z1 Z2 Z2 1 . 1 . Send Logic : Z2 Trip Logic : Rx + Z2 Open terminal echo : CB Open + Rx Permissive Overreach Scheme (CB Echo Logic)
- 25. Z4 Z4 Z1 Z1 Z2 Z2 Z3 Z2 Z1 T2 T3 Trip T2 Z3 Z2 Z1 T2 T3 Trip T2 & Z4 CB open & Z4 CB open Send Logic : Z2 Trip Logic : Rx + Z2 Open terminal echo : CB Open + Rx Weak Infeed echo : Z4 + Rx Permissive Overreach Scheme (WI Echo Logic) 1 & & & Rx Tx & Rx Tx 1 . 1 . 1
- 26. Z4 Z4 Z1 Z1 Z2 Z2 Z3 Z2 Z1 T3 Trip & T2 & LDOV Z3 Z2 Z1 T3 Trip & T2 & LDOV & Rx Tx Z4 CB open & Rx Tx Z4 CB open & & 1 . 1 . 1 1 Send Logic : Z2 Trip Logic : Rx + Z2 Open terminal echo : CB Open + Rx Weak Infeed echo : Z4 + Rx Weak Infeed trip : Z4 + LDOV reset + Rx Permissive Overreach Weak Infeed Trip Scheme
- 27. Provides better resistive coverage, especially on short lines, where MHO measuring elements are used For cases where one line terminal is open, open breaker echo logic can be used For cases of weak or zero infeed at one line terminal weak infeed logic can be used (reverse looking zone required) Permissive Overreach Transfer Trip - Advantages
- 28. Duplex signalling channel required Scheme is theoretically less secure then PUR as signalling channel is keyed for external faults If signalling channel fails then only Basic scheme logic will apply Permissive Overreach Transfer Trip - Disadvantages
- 29. Blocking Schemes
- 30. Z3 Z2 Z1 T3 Trip & T2 & Rx Tx 1 . Z3 Z3 Z1 Z1 Z2 Z2 Z3 Z2 Z1 T2 T3 Trip & T2 & Rx Tx 1 . Blocking Scheme - Internal Fault Send Logic : Z3 + Z2 Trip Logic : Rx + Z2
- 31. Z3 Z2 Z1 T3 Trip & T2 & Rx Tx 1 . Z3 Z3 Z1 Z1 Z2 Z2 Z3 Z2 Z1 T2 T3 Trip & T2 & Rx Tx 1 . Blocking Scheme - External Fault Send Logic : Z3 + Z2 Trip Logic : Rx + Z2
- 32. Blocking Scheme - Advantages Only simplex signalling channel required Provides better resistive coverage than PUR on short lines where MHO elements are used Fast tripping will still be possible at closed end of line for all fault positions with remote breaker open Fast tripping will still be possible at strong infeed terminal for all fault positions where remote terminal has no or weak infeed
- 33. Only 2 forward zones of protection available (unless relay has >3 Zones) If signalling channel fails then only Basic scheme logic will apply Current sensitivity is lower as tripping elements (Z2) are controlled by high set current level detectors (to ensure blocking elements (Z3/Z4) are more sensitive than tripping elements) Blocking Scheme - Disadvantages
- 34. Permissive less reliable - require a signal from remote relay plus local operation to trip Blocking less secure - require a signal from remote relay to prevent a trip Permissive schemes are marginally faster and more sensitive (timer plus high set current elements on Blocking scheme) Permissive Schemes vs Blocking Schemes
- 35. Teed Feeders
- 36. B A C' A' B' B' A' C A-A’ - Zone 1 reach of relay at A B-B’ - Zone 1 reach of relay at B C-C’ - Zone 1 reach of relay at C A’B’C’ Zone not covered by Zone 1 from any terminal. Hence schemes reliant on Zone 1 operation would not work (Z1 ext, PUR) Teed Feeders - No Zone 1 Coverage
- 37. B A C Zc Zb Za Ia Ic Actual impedance to fault from terminal A = Za + Zb Measured voltage at terminal A V = Ia.Za + (Ia + Ic).Zb Measured current at terminal A I = Ia Impedance measured by relay A V/I = Za + Zb + (Ic/Ia).Zb Relay therefore measures a greater impedance than the actual impedance and underreaches. Must allow for this underreach when setting Zone 2 elements to ensure correct scheme operation Teed Feeders - Underreaching
- 38. No infeed from terminal B. Fault therefore not covered by Zone 1 from any terminal. Hence schemes reliant on Zone 1 operation would not work (Z1 ext, PUR) B A C Teed Feeders - No/Weak Infeed at One Terminal
- 39. Relay at terminal B sees a reverse fault. No scheme will operate at this terminal. Fault clearance will be sequential following opening of breaker A from relay A Zone 1 element. B A C Teed Feeders - Problems (1)
- 41. DEF schemes are identical to Distance schemes DEF Forward replaces Zone 2, DEF Reverse replaces Zone 3/4 Reverse No equivalent to Zone 1 as the DEF elements can not have a defined reach, hence no schemes using Zone 1 can be replicated (Z1 ext, PUR) Directional Earth Fault Schemes
- 42. 21 Ea E b 67N 21 RF Independent signalling channel Independent signalling channels allows the use of different schemes for the distance and DEF elements, for example PUR distance with POR DEF Directional Earth Fault Schemes 67N
- 43. Shared signalling channels limits the use of schemes for the distance and DEF elements. Both use the same scheme logic. Directional Earth Fault Schemes 21 Ea Eb 67N 21 RF Shared Channel 67N