basic lines-protection.ppt

8/20/2019 Basic Lines-Protection.ppt

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Distance Relays

Introduction

1. The impedance relays also called distance relays areemployed to provide protection to transmission lines.

2. They are comparatively simple to apply, operate with

extremely high speed, and both primary and backupprotection features are inherent in them.

3. The impedance relay is made to respond to theimpedance between the relay location and the point

where fault is incident

4. The impedance is proportional to the distance to thefault, hence the name distance relay


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!istance "elaying #rinciple

1. $ distance relay compares the currents and voltages at therelaying point with %urrent providing the operating tor&ue and thevoltage provides the restraining tor&ue. 'n other words animpedance relay is a voltage restrained overcurrent relay, also

%alled under impedance relay

2. (ince the operating characteristics of the relay depend upon theratio of voltage and current and the phase angle between them,their characteristics can be best represented on an ")*

diagram where both +' ratio and the phase angle can be plottedin terms of an impedance "-*.


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Types of !istance "elays

1. 'mpedance relay

2. "eactance relay

3. /ho relay

4. /odified impedance relay


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1. (ince the distance relays are fed from the secondaries of line %Ts andbus #Tsline %+Ts, the line parameters are to be converted intosecondary values to set the relay as per re&uirements

2. 0sec 0pri'mpedance ratio

where 'mpedance ratio #.T."atio%.T."atio

3. or the lines, the impedance in 5hms per 6/ is approximately asunder7)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))6+ 01 02 8ine $ngle

)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))132 6+ 9.4 :9 to;9!eg.229 6+ 9.4 ;9 to


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0ones "eactance Time

)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))

0one ) 1 of 08 instantaneous

0one ) 2 199> of 08 - 49)=9> of 0(8 9.3 to9.4sec

0one ) 3 199> of 08 - 129> of 0(8 9.:to9. of 08 - 129> of 088 9.? to1.=sec

)))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))))where 08 #ositive se&uence impedance of line to be protected.

0(8 #ositive se&uence impedance of adacent shortest line.

088 #ositive se&uence impedance of adacent longest line


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/ain eatures in !istance (cheme

1. (tarters.

2. /easuring units.

3. Timers

4. $uxiliary relays


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Additional Features in distance schemes

1. #ower (wing blocking relay

2. +T fuse failure relay.

3. (witch onto fault relay

4. ault locator

=. $uto) reclosing scheme.

:. %arrier communication scheme


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Factors affecting distance relay operation

1. ault resistance.

2. 'nfeed effect.

3. @ranching)off effect.

4. 8oad encroachment


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eeder #rotection

1 5ver %urrent #rotectiona Time delayed non directional =1

b Time delayed directional :;

c 'nstantaneous =9

2 Around 5ver %urrent #rotection

a Time delayed non directional =1B

b Time delayed directional :;B

c 'nstantaneous =9B


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Instantaneous (50) protection

C Dsed for detecting high magnitude fault current

C (ame time delay regardless of fault magnitude or distance

C %o)ordination with down stream section cannot be maintained.


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#rotection for 3 #hase (ystem

a Three 5ver %urrent 5ne

Earth %urrent relayb Two 5ver %urrent 5ne Earth

%urrent relay

Ia

Ib

Ic

In=Ia+Ib+Ic

Ia

Ib

Ic

In=Ia+Ib+Ic


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E 5% 5% 5%

Earth ault

E 5% 5%


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E 5% 5%

#hase ault

5%E 5% 5%


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!irectional #rotection

B d f !i i l % l


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Beed for !irectional %ontrol

Aenerally re&uired if current can flow in both

directions through a relay locatione.g. #arallel feeder circuits

"ing /ain %ircuits

2.1 9.=9.? 9.11.31.;

B d f !i ti l % t l


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Beed for !irectional %ontrol

Aenerally re&uired if current can flow in both


"ing /ain %ircuits

rading has no! been lost "

2.1 9.=9.? 9.11.31.;

B d f !i ti l % t l


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Beed for !irectional %ontrolAenerally re&uired if current can flow in both


"ing /ain %ircuits

Relays operate for current flo! in direction indicated

(#ypical operating times sho!n)

9.? 9.19.= 9.?9.=9.1

"i / i %i it


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"ing /ain %ircuitFith ring closed 7

@oth load and fault current may flow in either

direction along feeder circuits

Thus, directional relays are re&uired

Bote7 !irectional relays look into the feeder

Beed to establish setting philosophy

=1 :;

=1

8oad

:; :;

8oad

:;:; :;

8oad

"i / i %i it


23/31

"ing /ain %ircuit$rocedure %

&' pen ring at A

rade % A' *' D' ' ,'

-' pen ring at A'

rade % A , D *

#ypical operating times sho!n'

.ote % Relays ,/ / D/ * may be nondirectional'

1.39.1

9.1 9.?9.=

9.?

9.=

@

$

@

E E

$

1.;

!

!

1.;

1.3

% %

"i ( t ith T (


24/31

"ing (ystem with Two (ources

!iscrimination between all relays is not possible due to different re&uirements

under different ring operating conditions.

or 1 7) @G must operate before $G

or 2 7) @G must operate after $G

.ot

ompatible}

@ @ % %

! !

F&

@

F-

$

$

"i ( t ith T (


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"ing (ystem with Two (ources

5ption 1

Trip least important source instantaneously then treat as normal ring main.5ption 2

it pilot wire protection to circuit $ ) @ and consider as common source

busbar.

$

@

5ption 15ption 15ption 1

5ption 2 5ption 2

=9

#F #F

# ll l d


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#arallel eeders

Bon)!irectional "elays 7)

H%onventional AradingI 7)

Arade J$G with J%G

and Arade J@G with J!G

"elays J$G and J@G have

the same setting.

=1

=1

$

!

8oad

=1 @

=1 %

$ K @

% K !

ault level

at JG

5 p e r a t i n g T i m e

# ll l d


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#arallel eeders

%onsider fault on one feeder 7)

"elays J%G and J!G see the same fault current

I2. $s J%G and J!G have similar settings bothfeeders will be tripped.

=1 $ =1%

=1 @ =1!

85$!

I& + I-I1

I2

# ll l d


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#arallel eeders

(olution7) !irectional %ontrol at J%G andJ!G

"elay J!G does not operate due to currentflow in the reverse direction.

=1 $ :;%

=1 @ :;!

85$!

I& + I-I1

I2

#arallel eeders


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#arallel eeders

(etting philosophy for directional relays

8oad current always flows in Jnon)operateG

direction. $ny current flow in JoperateG direction is

indicative of a fault condition.

=1 $ :;

E

=1 @ :;

%

!

8oad

=1


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#arallel eeders

Dsually, relays are set 7)

) =9> of full load current note thermal

rating

) '!/T rather than !T

) /inimum T./.(. 9.1

#arallel eeders $pplication Bote


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#arallel eeders ) $pplication Bote

#

@

@

!

!

8oad

8oad

If1

$ %

If1If22 If2

@%

!

Ifmax

$

Arade $ with @ with %

at If 1single feeder in service

Arade @ with ! at If 3'f 1upper feeder open at #

Arade $ with @ at If 2both feeders in service

) check that sufficient margin exists forbus fault at L when relay $ sees total

fault current If 2, but relay @ sees only

If 22.

If&

If-

/

/ /argin/

/

L

basic lines-protection.ppt

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