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8/20/2019 Basic Protection Technology
1/30
Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 1
Power System Structure
Generation Transmission / Sub transmission Distribution
Extra High Voltage 7! "V
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High Voltage 1&% "V11$ "V
"V
'edium Voltage && "V
%% "V
11 "V
'edium %# "V
Voltage %1 "V
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The *ur*ose o+ an ele,tri,al *o-er system is to generate and su**ly ele,tri,al energy to,onsumers( The system should be designed and managed to deli.er this energy to the
utilisation *oints -ith both reliability and e,onomy(
The *ur*ose o+ an ele,tri,al *o-er system is to generate and su**ly ele,tri,al energy to,onsumers( The system should be designed and managed to deli.er this energy to the
utilisation *oints -ith both reliability and e,onomy(
'any items o+ eui*ment are .ery ex*ensi.e0 and so the ,om*lete *o-er system re*resents a.ery large ,a*ital in.estment(
(
'any items o+ eui*ment are .ery ex*ensi.e0 and so the ,om*lete *o-er system re*resents a.ery large ,a*ital in.estment(
(
8/20/2019 Basic Protection Technology
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page %
System Disturbances
Short ir,uits in earthed systems
Symmetri,al 2& *hase3
Phase to Phase 2and Earth3
Phase to Earth
Earth 4aults in non e++e,ti.elyearthed systems
5.erload onditions
6nder+reuen,y/6nder.oltage
5.er.oltage
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page &
Prote,ti.e elaying is the most im*ortant +eature o+
*o-er system design aimed at minimising the
damage to eui*ment and interru*tion to ser.i,e in
the e.ent o+ +aults( 8t is there+ore a ,o9+a,tor
among other +a,tors resorted to im*ro.e reliability
o+ *o-er system(
Protective Relaying
Role of Protection
8/20/2019 Basic Protection Technology
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page #
The Purose of Protection
!ut it can"#imit the damage caused by shortcircuits
$hile"
Prote,ting *eo*le and *lant +romdamage
Sele,ti.ely ,learing +aults inmilise,onds
Prote,ting *lant +rom o.erload
,onditions
The rotection can not revent system faults%
Po-er system must o*erate in a sa+e manner at all times(
8/20/2019 Basic Protection Technology
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page !
&auses and Probability of System Disturbances
Causes
Operator Mistakes
Pollution/Condensation
Equipment failures, e.g. P.T.'s, Isolators
Transient Overvoltages
Probability
System faults (220/400 kV): 3p.a. and 100 km
10-20 kV metal clad switchgear:10-3p.a. and feeder
GIS switchgear: 5-10-2p.a. and bus
outdoor switchgear: 110/132 kV7*10
-2
p.a. and bus 220/275 kV 10-1p.a. and bus 400 kV 2*10-1p.a. and bus
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page
Sin,e *rote,ti.e relaying ,omes into a,tion at the time o+
eui*ment distress0 a ,ertain sa+eguard is ne,essary inthe unli"ely e.ent o+ its +ailure to a,t at the hour o+ need(
Hen,e0 t-o grou*s o+ *rote,ti.e s,hemes are generally
em*loyed 9
a3 Primary Prote,tion
b3 Ba,"9u* Prote,tion
Primary Prote,tion is the +irst line o+ de+ense0 -hereasba,"9u* relaying ta"es o.er the *rote,tion o+ eui*ment0
should the *rimary *rote,tion +ail(
Princiles of Relaying
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 7
The Primary Prote,tion has +ollo-ing ,hara,teristi, +eatures 9
1( 8t has al-ays a de+ined :one o+ o*eration(
%( 8t should o*erate be+ore any ba,"9u* *rote,tion
,ould o*erate0 there+ore0 it should be +aster in
o*eration(
&( 8t should be able to ,om*letely isolate the +ault
+rom all the ,urrent +eeding sour,es(
#( 8t should be stable +or all o*erating ,onditions(
Primary Protection
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page )
1( Ba,"9u* *rote,tion should *ro.ide su++i,ient time
+or the *rimary *rote,tion to *er+orm its duty(
%( Ba,"9u* *rote,tion ,o.ers a -ider :one o+
*rote,tion( There+ore0 there is al-ays a *ossibility
o+ large s,ale disturban,e0 -hen ba,"9u* relays
o*erate(
&( 6nder *rimary *rote,tion +ailure0 se.eral ba,"9u*
relays may o*erate +or ,om*lete isolation o+ +ault(
!ac'(u Protection
P T i i d Di t ib ti
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page ;
Primary *rote,tions +ailure ,ould be due to any o+ the+ollo-ing reasons 9
1( urrent or Potential Trans+ormer +ailure
%(
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 1$
Protection &oncet
The system is only as strong as the wea'est lin'*
D+STAN&E RE#A,
Circuit BreakerCT / VT
Protection Battery
&abling
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 11
!asic Protection
Re-uirements
Reliability deendability availability/high deendability 0 low ris' of failure to tri
Security stable for all oerating conditions %
high security 0 low ris' of over(tri
Seed high seed minimies damage
high seed reduces stability roblems
Selectivity tri the minimum number of circuit brea'ers
Sensitivity notice smallest fault value
Power Transmission and Distribution
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 1%
2ones of Protection
To limit the e3tent of the ower system that is disconnected when a fault
occurs% rotection is arranged in ones
2ones of rotection should overla% so that no art of the ower system is left
unrotected
#ocation of the &T connection to the rotection usually defines the one
4nit tye rotections have clear ones reach e.g Diff. Relay% RE) relay 2one reach deends on measurement of the system -uantities e.g 5& % E)%
distance relays . The start will be defined but the e3tent or 6reach7/ is sub8ect
to variation% owing to changes in system conditions and measurement errors.
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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Power Transmission and Distribution
No. 1 withEnergy Automation
Energy Automation Badiya Page 1&
Protection ( 5ne 5ut of Two Princile
System1
TripCoil1
Battery 1
↑
↑
System2
TripCoil2
Battery 2
Power Transmission and Distribution
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No. 1 withEnergy Automation
Energy Automation Badiya Page 1#
Redundancy &oncet of D& &ircuits
Battery 1Battery 2
Main Protection
87T
TR
TC 1
L-
Back-up Protection
50/51
TR
TC 2
Busbar Protection
87BB
TR
BF
L-
Trip remote infeed
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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No. 1 withEnergy Automation
Energy Automation Badiya Page 1!
)actors that influence fault current magnitude
9
> Short circuit ower of the infeed> :oltage level> #ine imedance> )ault resistance arc/> Treatment of star oint
+nfeed &onsumer#ine
Estimate of short circuit currents"
;edium :oltage 1< ': uto =0 +#ma3
E3tra ?igh :oltage @@
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No. 1 withEnergy Automation
Energy Automation Badiya Page 1
Earth faults" Star(oint configuration
R L
earthed system Peterson Coil isolated neutral• Earth fault =short circuit is recognised by normal over-current protection.• With low impedance earthing the residual current detection must be more sensitive.
• Earth faults = no short circuit• Supply is not disrupted• Earth fault must be alarmed and removed as fast as possible• Earth fault location is achieved with wattmetric earth fault detection
Power Transmission and Distribution
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No. 1 withEnergy Automation
Energy Automation Badiya Page 17
Protection &riterion ( &urrent
The o.er,urrent ,ondition is e.aluated 8? Suitable +or@
Additional ,riterion 9 Time
to ensure selectivity/Prote,tion@ 4uses in.erse time *rote,tion 28D'T3 de+inite time *rote,tion 2DT3
+
+S&min+#ma3
+>
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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No. 1 withEnergy Automation
Energy Automation Badiya Page 1)
Protection &riterion ( &urrent Difference
Evaluation of node +1 +@ += ... +n 0
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Energy Automation Badiya Page 1;
Protection &riterion ( +medance
)rom the voltage and current signals theimedance is calculated The imedance is roortional to the fault distance&haracteristic"
Additional criterion ( Time Re-uired for selectivity and bac'(u rotection/
Protection";ultile stage distance rotection
R
F
2G
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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No. 1 withEnergy Automation
Energy Automation Badiya Page %$
;easured signals and time grading rincile
Protected ob8ect
Protectiondevice
t
l
t1
t@
t=
21A ! 2@
A !
Exam*le distan,e *rote,tion
Power Transmission and Distribution
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No. 1 withEnergy Automation
Energy Automation Badiya Page %1
&omarison Protection Princile
Protected ob8ect
A !
Protectiondevice
Protectiondevice
Protection
device
communication
momentary .alues/binary de,isions
t
A B
Power Transmission and Distribution
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No. 1 withEnergy Automation
Energy Automation Badiya Page %%
Tyical Distance 2one &haracteristics
;?5(circle combined circle(
and straight line
characteristic
olarised;?5(circle
olygonal triing
characteristic
-uadrilateral/
A
S
S
external+ault
internal+ault
C
7
ϕΘ
C
7
S D $
S small
S large
S
74
<
starting :one
one &
one %
one 1
C
7
settable ar, ,om*ensationCC A
<7
8/20/2019 Basic Protection Technology
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Energy Automation Badiya Page %&
4urther Ty*i,al Prote,tion riteria
urrent in,rease6nder and o.er .oltageDire,tional ,om*arisonPhase ,om*arisonPo-er dire,tion
Phase angle5.er and under +reuen,y4reuen,y gradientHarmoni,sS*e,ial ,riteria in ma,hine *rote,tion
Power Transmission and Distribution
8/20/2019 Basic Protection Technology
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No. 1 withEnergy Automation
Energy Automation Badiya Page %#
Ty*i,al Prote,ted 5be,ts
Generators
Trans+ormers
Busbars
8/20/2019 Basic Protection Technology
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Energy Automation Badiya Page %!
Redundancy &oncets
Line Protection
LP1
LP2
≥1
1 out of 2 principle
trip line
Busbar Protection
Section1
&
2 out of 2 principle
trip section 1
Section2
Check
Zone
& trip section 2
Transformer Protection
Relay1
≥1
1 out of n principle
trip transformer
Relayn
.
.
.
Power Transmission and Distribution
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No. 1 withEnergy Automation
Energy Automation Badiya Page %
Stability #imits in Transmission System
<
1<
@<
=<
H<
B<
I<
J<
1=
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Energy Automation Badiya Page %7
)ailure Rate of Redundant Systems
<
8/20/2019 Basic Protection Technology
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$hy Digital ProtectionM
+ntegration of the rotection functions for one feeder"
)eeder rotection device
E3amle" overhead line of e3tra high voltage
Distance rotection with +>> or uGi>(e3itation
Three(ole reclosure Directional earth fault detection
)ault location
Event log
)ault recording
Power Transmission and Distribution
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Energy Automation Badiya Page %;
$hy Digital ProtectionM
Self-supervision
Raising of the availability
Plausibility control of the inut values
Suervision of the ad(conversion
+nternal testing of the comuter systems watch(dog/
Suervision of the memory chis
Testing the tri(relay(coil
Power Transmission and Distribution
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&ontact Terms
&ontacts rovide electrical oututs for triing and remote
indication uroses
Self-reset
The ,onta,ts remain in the o*erated ,ondition only -hile the ,ontrolling uantity is a**lied0
returning to their original ,ondition -hen it is remo.ed(
Hand or electrical reset
These ,onta,ts remain in the o*erated ,ondition a+ter the ,ontrolling uantity is remo.ed( They
,an be reset either by hand or ele,tri,ally by an auxiliary ele,tromagneti, element
A 'make' contact is one that ,loses -hen the relay *i,"s u*
A break contact is one that is ,losed -hen the relay is de9energised and o*ens -hen the relay *i,"s u*(
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