Download - EE 104 Lecture 1 – Fundamental Principles
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EE 104 LECTURE 1 FUNDAMENTAL PRINCIPLES OF
POWER SYSTEM PROTECTION
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Fundamental Principles
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Outlin1! A"n#$%&liti' in P#($ S)'t%'
2! I''u'* Pu$+#' &n, Fun-ti#n' #. P#($
S)'t% P$#t-ti#n
3! D'in C$it$i& .#$ P$#t-ti#n S)'t%
4! P$in-i+l' #. #n' #. P$#t-ti#n
! P$in-i+l' #. P$i%&$) &n, &-u+ P$#t-ti#n
6! Mt5#,' #. Di'-$i%in&ti#n
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Abnormalities in Power System
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Overcurrent
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Abnormalities in Power System
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OvercurrentSources of Overcurrent
Overload
O+$&ti#n #. E7ui+%nt/C#n,u-t#$ in 8-'' n#$%&l .ull l#&, 9$&t,:
-&+&-it) (5i-5 (5n it +$'i't' .#$ & 'u..i-int lnt5 #. ti%* (#ul, -&u',&%& #$ ,&n$#u' 5&tin
Shunt Faults (Short Circuits and round Faults!
W5n & +5&' -#n,u-t#$ t#u-5' &n#t5$ +5&' -#n,u-t#$ &n,/#$ t5
$#un, -&u'in 8-''i; -u$$nt &n, $7ui$' i%%,i&t int$$u+ti#n #.
t5 -i$-uit
Series Faults (Open Circuits!
W5n #n #$ t(# +5&' -#n,u-t#$' #+n, -&u'in 8-''i; un"&l&n-
-u$$nt &n, $7ui$' i%%,i&t int$$u+ti#n #. t5 -i$-uit
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Abnormalities in Power System
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Overcurrent
Protection #ethods
Protective devices that can sense overcurrents and
isolate faulted circuits Fuses
Circuit brea$ers (and protective relays!
%eclosers and sectionali&ers
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Abnormalities in Power System
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round PotentialSources of round Potential
round faults throuh an unrounded e)uipment
*ouch potentials Step potentials
Protection #ethods
System roundin +)uipment roundin
,
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Abnormalities in Power System
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Sure .oltae
Sources of Sure .oltaes
/ihtnin stro$es
Switchin sures Switchin in a lon line or
cable
Capacitor switchin
0nductive current choppin
Currentlimitin fuseoperation
Ferroresonance
armonics
Protection #ethods
esin
40/ of apparatus Protective devices
roundin
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0ssues and Purpose of Power
System Protection
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Safety *o prevent in6ury to personnel
+)uipment amae
*o minimi&e damae to system components
Service 0nterruption *o limit the e7tent and duration of service
interruption
+conomics *o minimi&e costs (+7penses and conse)uence
of failures!
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Functions of Protective Systems
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R-#ni
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Functions of Protective Systems
Primary Function Secondary Function
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T# -&u' t5 +$#%+t
$%#;&l .$#% '$;i- #.
&n) l%nt #n & +#($')'t% (5n it 'u..$' &
.&ult #$ (5n it 't&$t' t#
#+$&t in &n &"n#$%&l
%&nn$ t5&t %i5t -&u',&%&' #$ #t5$(i'
int$.$ (it5 t5 ..-ti;
#+$&ti#n #. t5 $'t #. t5
')'t%
*o provide indication of
the location and type offailure9 *his assists in
e7peditin repair and
provides means for
analy&in theeffectiveness of the fault
prevention
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Protective System esin Criteria
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19 %eliability
29 Speed
39 Selectivity
"9 Sensitivity
'9 +conomic
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Protective System esin Criteria
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19 %eliability
M&'u$ t5 ,$ #. -$t&int) t5&t t5
+$#t-ti; ')'t% (ill +$.#$% -#$$-tl)!
Rli&"ilit) ,n#t'= D+n,&"ilit) -$t&int) #. -#$$-t #+$&ti#n
S-u$it) &''u$&n- &&in't in-#$$-t #+$&ti#n
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Protective System esin Criteria
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29 Speed
R%#; .&ult .$#% t5 ')'t% &' 7ui-l) &'
+#''i"l
Cl&''i.i-&ti#n= In't&nt&n#u' n# intnti#n&l ti% ,l&)
>i5 '+, l'' t5&t 3 -)-l' 960 >< ')'t%:
Ti%,l&) intnti#n&l ti% ,l&) ".#$ t$i+&-ti#n
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Protective System esin Criteria
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39 Selectivity P$.#$%&n- #. +$#t-ti; ,;i-' t# 'l-t "t(n
t5#' -#n,iti#n' .#$ (5i-5 +$#%+t #+$&ti#n &n, t5#'
.#$ (5i-5 n# #+$&ti#n* #$ ti% ,l&) #+$&ti#n i'$7ui$,
I'#l&t .&ult, -i$-uit $'ultin in %ini%u% int$$u+ti#n'!
I%+l%nt, t5$#u5 #$one o% &rotection'
"9 Sensitivity Rl&)in 7ui+%nt %u't " 'u..i-intl) 'n'iti; '#
t5&t it (ill #+$&t (5n $7ui$,! Mu't ,i'-$i%in&t n#$%&l .$#% &"n#$%&l -#n,iti#n'!
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Protective System esin Criteria
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'9 +conomics
Rl&)' 5&;in -l&$l) ,.in'
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;one of Protection
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Ri#n' 9
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;one of Protection
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;one of Protection
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9": Li;t&n -i$-uit "$&$ (it5
.$'t&n,in CT!
9&: D&,t&n -i$-uit "$&$ (it5
"u'5in CT?'!
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;one of Protection
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9&: Li;t&n -i$-uit "$&$ (it5 .$'t&n,in CT!
9": D&,t&n -i$-uit "$&$ (it5 "u'5in CT'
9-: Li;t&n ,'in
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P$i%&$) &n, &-u+ P$#t-ti#n
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Provision must be made to clear the fault by
some alternate protection system should the
protection system fail to operate (fail to
clear the fault!
Primary Protection %&in +$#t-ti#n ')'t% .#$ &
i;n
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Primary and 4ac$up Protection
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Primary and 4ac$up Protection
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Mt5#,' #. Di'-$i%in&ti#n
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19 #ethod 4ased on /ocation of Fault
&: Di'-$i%in&ti#n ") ti%
": Di'-$i%in&ti#n ") -u$$nt %&nitu,
-: Di'-$i%in&ti#n ") ,i't&n- %&'u$%nt,: Di'-$i%in&ti#n ") ti% &n, ,i$-ti#n
: Di'-$i%in&ti#n ") ti% &n, -u$$nt %&nitu,
.: Di'-$i%in&ti#n ") ti% &n, ,i't&n-
: Cu$$nt"&l&n- ,i'-$i%in&ti#n5: P#($,i$-ti#n -#%+&$i'#n ,i'-$i%in&ti#n
i: P5&' -#%+&$i'#n ,i'-$i%in&ti#n
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#ethods of iscrimination
iscrimination by *ime
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Add time la featuresto the controllin relays
of a number of circuit
brea$ers to trip the
brea$er nearest the fault
prior to those farther offthe point of fault
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#ethods of iscrimination
iscrimination by Current#anitude
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%elays are set to pic$up
at a proressively hiher
current towards the
source
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#ethods of iscrimination
Di'-$i%in&ti#n ") Di't&n-
M&'u$%nt
Di'-$i%in&ti#n ") Ti% &n,
Di$-ti#n
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#ethods of iscrimination
Di'-$i%in&ti#n ") Ti% &n,
Cu$$nt M&nitu,
Di'-$i%in&ti#n ") Ti% &n,
Di't&n-
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#ethods of iscrimination
Cu$$nt &l&n-
Di'-$i%in&ti#n
P#($Di$-ti#n
C#%+&$i'#n Di'-$i%in&ti#n
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#ethods of iscrimination
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P5&' &nl #. -u$$nt &t
t5 n,' #. t5 +$#t-t,
'-ti#n i' -#%+&$,* (5i-5i;' in,i-&ti#n (5t5$
t5 .&ult i' internal #$
e7ternal
Phase Comparison iscrimination
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#ethods of iscrimination
29 #ethods based on
*ype of Fault
39 Combination of #ethodsSensitive to /ocation and
*ype of Fault
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&: $# +5&' '7un-
nt(#$
": N&ti; +5&' '7un-
nt(#$'
Phase and earth fault
protection
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Assinment
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1! W5&t &$ t5 &"n#$%&liti'
in P#($ S)'t%@ >#( ,#
( +$;nt t5%@2! W5&t i' t5 +u$+#' #.
$#un,in@ W5) i' it
i%+#$t&nt@
3! W5&t i' t5 ,i..$n-
"t(n #;$l#&, -u$$nt&n, .&ult -u$$nt@
"9 For the system shown in the fiure
below< the fault F produces these different
responses at various times=
(a! %1 41and %2< 42operate>
(b! %1 41