Presentation for Protection by Zia Vai

8/12/2019 Presentation for Protection by Zia Vai

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Power System

1) Power Generation

2) Power Transmission3) Power Distribution


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Power Distribution

Protection System

1) Feeder Protection2) Transformer Protection


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Feeder Protection

1) Over Current Protectiona) Time delayed non directional !1)b) Time delayed directional "#)c) $nstantaneous !%)

2) Ground Over Current Protection

a) Time delayed non directional !1&)b) Time delayed directional "#&)c) $nstantaneous !%&)


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Inverse Time delayed protection (51/67, 51N/67N)

' (llows time delay coordination wit down stream' O*eratin+ time inversely *ro*ortional to current' O*erates slower for low ma+nitude faults' O*erates faster for ,i+ ma+nitude faults' O*eratin+ c aracteristic

$nverse- very inverse- e.tremely inverse

$n modern relay definite time delay tri**in+ can be added alon+inverse c aracteristic


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Instantaneous (50) protection

/ 0sed for detectin+ i+ ma+nitude fault current

/ Same time delay re+ardless of fault ma+nitude or distance

/ Co ordination wit down stream section cannot bemaintained


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Protection for 3 P ase System

a) T ree Over CurrentOne art Current relay

b) Two Over CurrentOne art Current relay

Ia

Ib

Ic

In=Ia Ib Ic

Ia

Ib

Ic

In=Ia Ib Ic


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4F O4C O4C O4C

art Fault

4F O4C O4C


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4F O4C O4C

P ase Fault

O4C4F O4C O4C


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5elay 6asics

/ lectromec anical 5elays 7 8a+nets- coils- transformers- s*rin+s- etc

/ Static or lectronic 7 Transistors- diodes- o*am*s

/ (lso ma+nets- coils- transformers- etc 7 Can du*licate 48 relay functions

/ Di+ital or 8icro*rocessor 7 Com*uters9

/ (lso ma+nets- coils- transformers- etc

7 Can du*licate 48 relay functions


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5elay 6asics

/ &on directional 7 Detect fault in any direction 7 O*erate w en :uantity e.ceeds *ic;u* value

/ Directional 7 0se volta+es- currents- and an+les to determine

fault direction/ Tri* for faults in front of relay/ 6loc; for faults be ind relay

7 O*erate w en :uantities e.ceed *ic;u* value andcorrect direction is determined


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Time,!econds

"ultiples o# $% &urrent

1 21 1%

$nverse

Definite Time

8odern5elay


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Time,!econds

"ultiples o# $% &urrent

1 21 1%

$nverse

Definite Time

8odern5elay


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6 (

!1

Fault

6rea;er ( Tri*Time

Distance

!1

Current Direction

Protection for Parallel Feedin+

6rea;er 6 Tri*Time

61 (1

!1

6rea;er ( Tri*Time

!1

Current Direction

6rea;er 6 Tri*Time

C

!1

6rea;er 6 Tri*Time

>

Fault

?

"#

"#


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T i m e

Current

6461 !1) (4(1 !1)

Fault at ?

=C

T i m e

T6461!1) @T6461"#)

6 "#) (1

Fault at >

=

Current


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5elay Co ordination

( ) TMS

I T

=

1

14.002.

$ A8ulti*le of Fault Current $n 5elay

$ C &ormal $nverse Curve :uation


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Overcurrent Protection !%-!1)

(

6

C

132 ;B 433 ;B (

6

C

5elay s)5elay s)

!%4!1 !%4!1!%4!1&

!1G&


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Transformer Differentials #)/ Detect faults wit in differential one

7 6etween CTs wit in *rotective one) 7 $mmune to e.ternal faults

/ Eill not see turn to turn fault/ CT Connections

7 Delta for wye windin+ 7 Eye for delta windin+ 7 Com*ensate for transformer * ase s ift


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.ternal Fault

'1 '

p

I1

I *I1*

I

I p + 0


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$nternal Fault

'1 '

p

I1

I1*

I p = I1* I *

I *

I


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# CT ConnectionsDyn1


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# CT Connections

' '

' '

' '

$(

$6

$C

$C

$6

$(

$aA$( $6

$bA$6 $C

$cA$C $(

$c

$b

$a

$(

$C

$6


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Differential ProtectionCannot Protect TotalSecondary Eindin+


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5 F Protection

(

6

C

132 ;B 433 ;B (

6

C

5elay s)

5 F

o*erates only for Secondary Eindin+ Fault


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5 F Protection

(

6

C

132 ;B 433 ;B (

6

C

5elay s)

5 F

$nside Fault O*eratin+


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1 -v .us

-v .us

11-v .us

5e:uired $nformation

1) Fault evel at 132 ;v

2) H $m* of all Transformer < 8B( 5atin+

3) 33 Iv ine $m*


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Presentation for Protection by Zia Vai