Transmission Line Protection

TRANSMISSION LINE TRANSMISSION LINE

PROTECTIONPROTECTION

TRANSMISSION LINE TRANSMISSION LINE

PROTECTIONPROTECTION

April 8, 2023 1Protection Courses


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


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

15. ZONE 1 EXTENSION


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


MHO CHARACTERISTICS

MHO


MHO CHARACTERISTICS


QUADRILATERAL CHARACTERISTICS

Quadrilateral


OFFSET MHO CHARACTERISTICS



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


VR

VB

VY

VRB

VBY

VYR

POLARIZATION METHODS


S/Stn 1 S/Stn 2 S/Stn 3

Time

Zone 3R

Zone 3R

Zone 3R

Zone 2

Zone 2Zone 3R

Zone 2

Relay A

Relay B

Relay C

Relay D

Zone 3F

Zone 2Zone 3

Zone 1

Zone 1

Zone 1

Zone 1

ZONES SETTING CRITERIA


A B C

X

R

Zone 1

Zone 3Zone 2

ZONES SETTING CRITERIA

Zone 4


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


AC SOTF - Used where VT is on LINE SIDE of the CBIF Current and Voltage have been Dead for 10 SecsAND the Current Rises ABOVE 30% of NominalAND Voltage remains BELOW 20% of NominalTHENRemove the Time Delay from Zone 3ANDAllow tripping on Overcurrent onlyFOR200ms

DC SOTF - Used where VT is on BUSBAR SIDE of the CBWhen Circuit Breaker Manual Close Handle is OperatedRemove the Time Delay from Zone 3FOR 400ms(Longer delay allows for CB Closing time)

SOTF ALGORITHMS


Power Swing Outer boundary

Power Swing Inner boundary

Transittime

Power swing locusZone 1

Zone 2

Zone 3

If the System Impedance Remains in the Power SwingDetection Zone for longer than the PSD Transit Time (Nominally 50 ms)POWER SWING ALARMwill Operate

POWER SWING DETECTION & BLOCKING


POWER SWING DETECTION & BLOCKING


LOAD ENCROACHMENT


LOSS OF POTENTIAL


Zone 2Carrier Aided Trip

S/Stn 1 S/Stn 2

Time

Zone 1 (No Operation)

Distance

Distance

Zone 1

Relay B

Relay C

Relay A Signalling Channel

Zone 2Time Delayed Trip

Operation of Zone 1 sends signal to remote end

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

ALLOWS INSTANTANEOUS TRIPPING OVER 100% OF THE LINE LENGTH

Zone 2

SIGNALLING CHANNEL REQUIRED BETWEEN ENDS

PERMISSIVE UNDER REACH



S/Stn 1 S/Stn 2

Time


Distance

Distance

Relay B

Relay C


Zone 2Time Delayed Trip

Instantaneous Operation of Zone 2 sends signal to remote end

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

Zone 2

Zone 2 InstantaneousZone 1



PERMISSIVE OVER REACH



S/Stn 1 S/Stn 2

Time


Distance

Distance

Zone 1

Relay B

Relay C


Zone 4 - Blocking

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

Zone 2



BLOCKING SCHEME



S/Stn 1 S/Stn 2

Time


Distance

Distance

Zone 1

Relay B

Relay C


Zone 4 - Blocking (No Operation)

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

Zone 2



BLOCKING SCHEME

24Protection Courses

CURRENT REVERSAL

April 8, 2023


CURRENT REVERSAL


CURRENT REVERSAL


RelayA

RelayB

RelayC

S/Stn 1 S/Stn 2

RelayC

S/Stn 3

Time

Gives improved fault clearancetime for fault @ this position

Will trip CB @ 'A' forfault @ this position

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

Zone 2 Zone 3F

Distance

Distance

Trip

Reclose

Zone 1 Ext

Zone 1

ZONE 1 EXTENSION SCHEME


WEAK IN FEED LOGIC


SERIES COMPENSATION

• Used to increase load capacity

• Improve power system stability

• Improve load division on parallel paths

• Reduce transmission losses


SERIES COMPENSATION

• Voltage reversal


• 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

Ia

Z M OFault

Ib

Double Circuit Line

MUTUAL COMPENSATION 1


• 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

MUTUAL COMPENSATION 2


CCVT TRANSIENT


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


CCVT TRANSIENT


DIRECTIONAL EARTH FAULT 1

• Unrestricted Characteristic

– Operates for any fault current above setting in selected direction

• Detects high impedance earth faults

– Operate quantity - residual current

– Polarising quantity - residual voltage

X

R

Line Angle


DUAL DIRECTIONAL EARTH FAULT

• 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

X

R

Line Angle

Forward DEF

Reverse DEF


• 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

DIRECTIONAL EARTH FAULT 2

Transmission Line Protection

Documents

operation zone

instantaneous zone

r zone

protection courses

reach operation of zone

power swing detection

relay b relay c relay

unit protection