3.Application of Dist Prot With KD Appendix

8/6/2019 3.Application of Dist Prot With KD Appendix

1/41

Knowledge Is PowerSMApparatus Maintenance and Power Management

for Energy Delivery

Application of Distance ProtectionJay Gosalia

Vice President of Marketing

Doble Engineering Company


2/41


for Energy Delivery

Distance Protection

3 Zones of protection

Zone 1 operates with no intentional time

delay

Zone 2 provides back up protection to Zone

1 and operates with some time delayZone 3 typically has offset characteristic

and has a time delay longer then Zone 2

Zone 2 and Zone 3 are used in pilotscheme if employed


3/41


for Energy Delivery

General Application Rules

Zone 1 protects 80-85% of line length AB

Zone 2 protects line AB + 50% of line BC Zone 3 Protects AB + Line BC + 20-30% of line CD + 20-30%

of line behind terminal A

Zone 1 protects 80-85% of line length AB

Zone 2 protects line AB + 50% of line BC

Zone 3 Protects AB + Line BC + 20-30% of line CD + 20-30%

of line behind terminal A

AB DC

Time

Zone 1

Zone 2Zone 3


4/41


for Energy Delivery

Reach Setting Criteria : Zone 1

Zone 1 should never over reach for the faults on or

beyond remote terminal

Considering 5% accuracy of CTs and PTs maximum

reach of Zone 1 can be 90% of line length AB

Considering accuracy of Zone 1 protection 5% and safety

margin of 5% Zone 1 reach can be 80% of the line length. In some instances based on the previous practices Zone

1 is set to 90% of line length

It is safe to set Zone 1 reach 80% of line length in general

A BDC

Zone 1


5/41


for Energy Delivery

Zone 1: Requirements

Should cover the protected circuit and shouldprovide good fault resistance coverage Fast operation for limiting the system disturbance Directional discrimination for security and reliability

AB

DC

Zone 1


6/41


for Energy Delivery

Reach Setting Criteria : Zone 2

Zone 2 should always over reach for the faults on or

beyond remote terminal Zone 2 should always reach beyond the remote terminal andcover at least 50% of next line section

Zone 2 time delay should be larger then the operating timeof Protection + CB (at terminal C of line CD) + safety margin

Breaker fail timer co ordination is required

Zone 2 is used in the pilot aided trip scheme to provideinstantaneous protection for faults anywhere on line BC

AB C

D

Zone 2


7/41


for Energy Delivery

Zone 2 Time Delay : Criteria

Determine Zone 2 time if Breaker fail protection is employed

Breaker fail protection clears the fault by tripping back up breaker ifthe primary breaker fails to clear the fault after the protection trip

For fault on line CD, protection at breaker 5 will see the fault andissues a trip command to breaker 5 and at the same time initiatesbreaker fail protection

If breaker 5 trip it resets the breaker fail protection

The fault is seen by the protection at breaker 3, in Zone 2.

If breaker 5 fails then Breaker fail protection trip all breakers at bus C

What should be the Zone 2 time delay for protection at breaker 3?

1 2 3 4 5 6

B CA D

Zone 2


8/41


for Energy Delivery

Breaker Fail Scheme

Breaker fail scheme principle Consists of a timer, high speed pick up/drop out over

current protection and lock out protection

Some time re-trip protection is employed Needs 52a breaker input to sense breaker status

When protection operates it initiates breaker fail

scheme Timer is starts and seals in with the high speed over

current protection

Issues re trip command to second trip coil of the breaker

If breaker trips then 52a resets the timer and at the sametime over current protection.

If breaker fails to trip then timer times out and picks up lockout protection to trip the back up breakers connected to the

bus


9/41


for Energy Delivery

Breaker Fail Protection Logic

OR62X

62Y

AND50 Timer86


10/41


for Energy Delivery

Timing Diagram : Normal Operation

Operating

Time of CB: 2Cy.

Protection

Trip: 1Cy.

Drop out time

Of current prot : 1 Cy.

Margin: 5 Cy.

Breaker fail timer time delay : 7 Cy.

Breaker fail protection start


11/41


for Energy Delivery

Timing Diagram : Failed CB

Operating

Time of CB: 2Cy.

Protection

Trip: 1Cy.

Drop out time

Of current prot : 1 Cy.

Margin: 5 Cy.

Margin

7 Cy.

Operating

Time of CB: 2 Cy.Breaker fail

Protection trip : 0.5 Cy

Breaker fail timer time delay : 7 Cy.

Breaker fail protection start

Remote Zone 2 Back up protection operation time :say 20 Cy.


12/41


for Energy Delivery

Reach Criteria Zone 3

Zone 3 is a back up protection and last resort for the

isolation of the fault if everything fails

Time Delayed protection. Time delay is longer thenZone 2 delay

When a very long line is following the short line Zone

3 reach may be very long Can interfere with load on the line

Lens characteristic is a potential solution

It is used in the pilot aided protection when blocking

scheme is employed to detect the fault direction

Typically set in the offset mode to cover the reverse

fault


13/41


for Energy Delivery

Zone 3 : Load Encroachment

Load


14/41


for Energy Delivery

Zone 1 Reach : 3 Terminal Line

X

Y

ZIx

Iy

Ix + Iy

F

Fault voltage at X = VF

= Ix*ZF

+ Iy* (1-d)ZFFault current at X = Ix

Apparent Impedance at X =VF/IF= VF/Ix =ZF + Iy/Ix (1-d)ZFAdditional impedance due to in feed = Iy/Ix (1-d)ZFFault will be seen farther: Protection will not trip

Fault voltage at X = VF = Ix*ZF + Iy* (1-d)ZFFault current at X = Ix

Apparent Impedance at X =VF/IF= VF/Ix =ZF + Iy/Ix (1-d)ZFAdditional impedance due to in feed = Iy/Ix (1-d)ZFFault will be seen farther: Protection will not trip

d


15/41


for Energy Delivery

Zone 1 Reach : 3 Terminal Line

X

Y

ZIxF

Lets Set the reach considering maximum in feed so protection tripsNow say breaker at Y is out for maintenance

Now the fault in the next line section will be seen as internal

Protection will trip for the external fault

Lets Set the reach considering maximum in feed so protection trips

Now say breaker at Y is out for maintenance

Now the fault in the next line section will be seen as internal

Protection will trip for the external fault


16/41


for Energy Delivery

Rules for Zone 1 and Zone 2 Reach

Zone 1 should never overreach and Zone 2 shouldalways over reach the remote terminal

For 3 terminal line set the

Zone 1 Reach As if there is no in feed

Set the Zone 1 only up to tap point

Zone 2 Reach

Set the Zone 2 reach considering maximum in feed

General rule and good practice for Zone 1 Its better not to trip for an internal fault then to trip for the

external fault


17/41


for Energy Delivery

Phase to Phase Fault

Phase to phase fault MHO is an ideal characteristic Fault resistance is arc resistance

Fault current = V/(Zs+ZL+ Rarc)

Arc resistance inversely proportional to current and directlyproportional to line spacing

Rarc = (8750 * L)/ I1.4

For strong source: lower Zs, creates high fault current,

produces lower arc resistance For weak source : higher Zs, creates lower fault current,

produces higher arc resistance

For phase to phase fault MHO characteristic adjusts basedon the source impedance

A

B

C

GZs


18/41


for Energy Delivery

Arc Resistance


19/41


for Energy Delivery

Phase to Phase Fault: Fault Resistance

Phase-Phase faultsconsist only of arcresistance Earth faults consist ofarc and tower footingresistance

A i t C


20/41


for Energy Delivery

Arc resistance Coverage

ZR

Zs

Rarc

ZR

Zs

Rarc

Strong source, Lower Zs, smaller Rarc, lower expansion = Good Rarc coverage

Weak source, Higher Zs, larger Rarc, higher expansion = Good Rarc coverageStrong source, Lower Zs, smaller Rarc, lower expansion = Good Rarc coverage

Weak source, Higher Zs, larger Rarc, higher expansion = Good Rarc coverage

P S i


21/41


for Energy Delivery

Power Swing

Variation in power flow Sudden removal of fault

Loss of synchronism between ends of power system

Change in the direction of power flow

Protection on the system may see the impendencemoving from load condition to its operating zone.

During transient condition Protection should not trip

Only protection that requires system disconnectionat suitable point should trip

To prevent tripping some type of sensing need to

be employed to distinguish between power swingand actual fault

Requires Power Swing Blocking Protection

P S i


22/41


for Energy Delivery

Power Swing

Power Flow from A to B EA leads EB by angle

Total impedance : Z=ZSA +ZL+ZSB

Current I = (EA-EB)/Z

Voltage E at the Relay = EA-I*ZSA

Power Flow from A to B EA leads EB by angle

Total impedance : Z=ZSA +ZL+ZSB

Current I = (EA-EB)/Z

Voltage E at the Relay = EA-I*ZSA

A B

EA EB

21

ZsBZL

ZsA

E

I

P S i N l C diti


23/41


for Energy Delivery

Power Swing : Normal Condition

ZR=E / I

B

EA EB

21

ZsBZL

ZsA

E

I

EB

I I*ZSA

EA

E

EA - EB

EA - EB

P S i Ab l C diti


24/41


for Energy Delivery

Power Swing : Abnormal Condition

ZR is much smaller then ZR

E is small

EA-EB is large due large

ZR is much smaller then ZR E is small

EA-EB is large due large

I

EB

I*ZSAEA

E EA - EB

ZR=E / I

B

EA EB

21

ZsBZL

ZsA

E

I

Power Swing


25/41


for Energy Delivery

Power Swing

EB

II*ZSA

EA

E

EA - EB

EA - EBEB

I*ZSAEA

E EA - EB

Power Swing : Locus


26/41


for Energy Delivery

Power Swing : Locus

P.S. LOCUS

LOAD

R

PSB

ZSB

Z L

ZSA

O

Z

X

MHO Characteristic : Power Swing


27/41


for Energy Delivery

MHO Characteristic : Power Swing

P.S. LOCUS

LOAD

R

ZSB

Z L

ZSA

X

QUAD Characteristic : Power Swing


28/41


for Energy Delivery

QUAD Characteristic : Power Swing

P.S. LOCUS

LOAD

R

ZSB

Z L

ZSA

X

Switch ON to Fault


29/41


for Energy Delivery

Switch ON to Fault

Ensures inst. Trip under switch on to fault condition whenline is energized with earthing clamps connected tobreaker terminals

Need for SOTF

Protection against close up 3 Phase Faults when line

VTs are used When used with Bus PT pre fault memory polarization

can provide tripping through distance protection

Distance Protection: Switch ON to


30/41


for Energy Delivery

Fault

Distance Protection: VT Supervision


31/41


for Energy Delivery

Distance Protection: VT Supervision

Condition shall be Detected when;3Vo > 20% of VN (L-N) & 3Io < 20% of IN

FUSE FAILURE WILL CAUSE VOLTAGE UNBALANCEAND HENCE VO(V2) BUTNO CURRENT UNBALANCE IO(I2)UNBALANCED FAULTS CAUSE BOTH VOLTAGE/CURRENTUNBALANCE,PREVENTING VTS OPERATIONFUSE FAIL SUPERVISION IS BLOCKED FOR 150 TO 300ms FOLLOWING LINEENERGIZATION IN ORDER NOT TO OPERATE FOR UNEQUAL POLE CLOSING &ALSO DURING AUTO-RECLOSING

Distance Protection: Setting Criteria


32/41


for Energy Delivery




33/41


for Energy Delivery




34/41


for Energy Delivery




35/41


for Energy Delivery




36/41


for Energy Delivery




37/41


for Energy Delivery


PERMISSIVE OVERREACHING SCHEMES AREADOPTED FOR SHORT LINES ( ALSO CALLEDDIRECTIONAL COMPARISON SCHEMES) ADVANTAGESARE; BETTER PERFORMANCE FOR HIGH RESISTANCEFAULTS. SUPERIOR TO PILOT WIRE AS DIGITAL DECISIONSARE EXCHANGED AND NOT ANALOGUE SUPERIOR TO PHASE COMPARISON WHICHREQUIRES FAITHFUL TRANSMISSION OF PHASEINFORMATION.



38/41


for Energy Delivery

g

Communication signal is sent to remoteend when the fault is detected in the reversedirection. Tripping is achieved when thisblocking signal is not received within a timeT0 (20-40 ms) and the local relay hasdetected a fault in the forward direction.



39/41


for Energy Delivery

g



40/41


for Energy Delivery

g

BLOCKING SCHEMES ARE USED WHENCOMMUNICATION SIGNALS SHALL NOTBE TRANSMITTED OVER FAULTY LINEFOR RELIABILITY REASONS


41/41


for Energy Delivery

3.Application of Dist Prot With KD Appendix

Documents

Transcript of 3.Application of Dist Prot With KD Appendix