Day 2 Transmission Line Protection

TRANSMISSION LINE PROTECTION 20 December 2010

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TUTORIAL SCOPE 1. FUNDAMENTALS 2. CHARACTERISTICS 3. POLARIZATION 4. ZONES SETTING CRITERIA 5. MHO VS QUADRILATERAL 6. SWITCH ON TO FAULT 7. POWER SWING BLOCKING/TRIPPING 20 December 2010

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TUTORIAL SCOPE 8. LOAD ENCROACHMENT 9. LOSS OF POTENTIAL 10. UNIT PROTECTION 11. PERMISSIVE UNDER REACH 12. PERMISSIVE OVER REACH 13. CARRIER BLOCKING 14. CURRENT REVERSAL 20ZONE December 15. 1 2010 EXTENSIONProtection Courses

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TUTORIAL SCOPE 16. WEAK IN-FEED 17. SERIES COMPENSATION 18. MUTUAL COMPENSATION 19. AUTO RECLOSER 20. STUB PROTECTION 21. CCVT TRANSIENT 22. DIRECTIONAL EARTH FAULT 20 December 2010

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MHO

MHO CHARACTERISTICS 20 December 2010

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MHO CHARACTERISTICS

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Quadrilateral

QUADRILATERAL CHARACTERISTICS 20 December 2010

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OFFSET MHO CHARACTERISTICS

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POLARIZATION METHODS  SELF POLARIZATION  Terminal faults will not cover  CROSS POLARIZATION  Use other healthy phase voltages  Terminal three phase fault will not cover  MEMORY POLARIZATION  Covers all type of faults 20 December 2010

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VRB VB VBY

VR VY VYR

POLARIZATION METHODS

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ZONES SETTING CRITERIA S/Stn 1

S/Stn 2

Relay A

Time

Zone 3R

Relay B

Zone 2

Relay C

Zone 2

Zone 1

Relay D

Zone 3F

Zone 3R Zone 1

Zone 3R

Zone 3

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S/Stn 3

Zone 2

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Zone 2

Zone 1

Zone 1

Zone 3R

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ZONES SETTING CRITERIA

X A

B

C

Zone 4 Zone 1 Zone 2

Zone 3

R

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SWITCH ON TO FAULT     

SWITCH ON TO FAULT. Failure to remove Earth Clamps after CB Maintenance Practically Zero Impedance in fault path. Fault Point is at the Origin - Boundary condition for Zones 1 & 2 For a 3-Phase fault, cross-polarising will have no effect

SOTF Fault Point

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SOTF ALGORITHMS AC SOTF - Used where VT is on LINE SIDE of the CB IF Current and Voltage have been Dead for 10 Secs AND the Current Rises ABOVE 30% of Nominal AND Voltage remains BELOW 20% of Nominal THEN Remove the Time Delay from Zone 3 AND Allow tripping on Overcurrent only FOR 200ms DC SOTF - Used where VT is on BUSBAR SIDE of the CB When Circuit Breaker Manual Close Handle is Operated Remove the Time Delay from Zone 3 FOR 400ms (Longer delay allows for CB Closing time) 20 December 2010

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Power Swing Outer boundary If the System Impedance Remains in the Power Swing Detection Zone for longer than the PSD Transit Time (Nominally 50 ms) POWER SWING ALARM will Operate

Power Swing Inner Zone 3

boundary

Zone 2

Power swing locus

Zone 1

Transit time

POWER SWING DETECTION & BLOCKING

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POWER SWING DETECTION & BLOCKING

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LOAD ENCROACHMENT

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LOSS OF POTENTIAL

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Operation of Zone 1 sends signal to remote end



Instantaneous trip if  Zone 1 Operation  Zone 2 + Signal from Remote end



S/Stn 1

SIGNALLING CHANNEL REQUIRED BETWEEN ENDS

PERMISSIVE UNDER REACH

Relay A

S/Stn 2

Relay B

Signalling Channel Zone 2 Carrier Aided Trip

Time

Relay C

Zone 2 Time Delayed Trip

Distance

Zone 1 (No Operation)

Zone 1 

Zone 2

Distance

ALLOWS INSTANTANEOUS TRIPPING OVER 100% OF THE LINE LENGTH 20 December 2010

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Instantaneous Operation of Zone 2 sends signal to remote end



Instantaneous trip if  Zone 1 Operation  Zone 2 + Signal from Remote end



SIGNALLING CHANNEL REQUIRED BETWEEN ENDS

PERMISSIVE OVER REACH S/Stn 1

Relay A

S/Stn 2

Relay B

Signalling Channel Zone 2 Carrier Aided Trip

Time

Relay C

Zone 2 Time Delayed Trip

Distance

Zone 1 (No Operation)

Zone 2

Zone 2 Instantaneous Zone 1 Distance



ALLOWS INSTANTANEOUS TRIPPING OVER 100% OF THE LINE LENGTH 20 December 2010

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BLOCKING SCHEME

Operation of Zone 4 sends blocking signal to remote end



Instantaneous trip if  Zone 1 Operation  Zone 2 + No blocking Signal from Remote end  WITHIN the Permissive Trip Time



SIGNALLING CHANNEL REQUIRED BETWEEN ENDS

S/Stn 1

Relay A

S/Stn 2

Relay B

Signalling Channel

Relay C

Zone 2 Carrier Aided Trip

Time

Distance

Zone 1 (No Operation)

Zone 1 

Zone 2

Zone 4 - Blocking

Distance

ALLOWS INSTANTANEOUS TRIPPING OVER 100% OF THE LINE LENGTH 20 December 2010

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Operation of Zone 4 sends blocking signal to remote end



Instantaneous trip if  Zone 1 Operation  Zone 2 + NO BLOCKING SIGNAL from Remote End  WITHIN the Permissive Trip Time



S/Stn 1

SIGNALLING CHANNEL REQUIRED BETWEEN ENDS

BLOCKING SCHEME

Relay A

S/Stn 2

Relay B

Signalling Channel

Relay C

Zone 2 Carrier Aided Trip

Time

Distance

Zone 1 (No Operation)

Zone 1



Zone 2

Distance

Zone 4 - Blocking (No Operation)

ALLOWS INSTANTANEOUS TRIPPING OVER 100% OF THE LINE LENGTH 20 December 2010

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CURRENT REVERSAL

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CURRENT REVERSAL

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CURRENT REVERSAL

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No Signalling used between ends Used with Auto-Recloser only Results in More Breaker Operations

  

Gives improved fault clearance time for fault @ this position

S/Stn 1

Relay A

S/Stn 2

Relay B

Will trip CB @ 'A' for fault @ this position

Relay C

S/Stn 3

Relay C

Time

Trip

Zone 1 Ext Distance

Reclose

Zone 1

Zone 2

Zone 3F Distance

ZONE 1 EXTENSION SCHEME 20 December 2010

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WEAK IN FEED LOGIC

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SERIES COMPENSATION • Used to increase load capacity • Improve power system stability • Improve load division on parallel paths • Reduce transmission losses

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• Voltage reversal

SERIES COMPENSATION

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Ia Double Circuit Line

ZMO

Fault

Ib

•

•

•

COUPLING BETWEEN LONG LINES CAN HAVE A SIGNIFICANT EFFECT ON DISTANCE  PROTECTION MEASUREMENT ONLY AFFECTS ZERO SEQUENCE COMPONENT (PPS AND NPS COMPONENTS ARE  BALANCED AND THEREFORE SUM TO ZERO)

IF RELAY NOT COMPENSATED FOR EARTH RETURN AND MUTUAL EFFECTS Z1 WILL BE OVER‐ ESTIMATED AND THE RELAY WILL UNDER‐REACH

MUTUAL COMPENSATION 1 20 December 2010

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MUTUAL COMPENSATION 2

• •

•

When one of the lines is out of service and earthed at both ends Energise a Status Input SWITCH TO ALTERNATE SETTINGS group

ALTERNATE SETTING GROUP uses – Increased Earth Fault Compensation Factor to take account of the Zero Sequence Mutual Coupling due to the parallel line

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CCVT TRANSIENT

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CCVT TRANSIENT

 Distance element may over reach  CCVT Trans. Reduce the fundamental component of the fault voltage results in decrease in the calculated impedance  High capacitance reduced transient effect  Passive Ferro-resonance reduced transient effect

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CCVT TRANSIENT 20 December 2010

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•

Unrestricted Characteristic – Operates for any fault current above setting in selected direction

X •

Detects high impedance earth faults – Operate quantity - residual current – Polarising quantity - residual voltage



Line Angle

R

DIRECTIONAL EARTH FAULT 1 20 December 2010

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DUAL DIRECTIONAL EARTH FAULT X •

TWO Unrestricted Characteristics

• • •

Common Line Angle Setting Different Operating Current Settings Forward DEF – Operates on Current above FWD setting in FORWARD direction Reverse DEF – Operates on Current above REV setting in REVERSE direction

•

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Forward DEF

Line Angle



R

Reverse DEF

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DIRECTIONAL EARTH FAULT 2 • •

Discrimination using DTL or IDMTL Time Grading (DEF Direct Trip) • OR High Speed operation using a Signalling Channel (DEF POR)

Operation of both DEF elements allows instantaneous tripping

• • •

If no Signalling Channel is available OR Signalling Channel fails

•

RELAY CAN OPERATE AS BACK-UP TIME GRADED OVER CURRENT 20 December 2010

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