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Electrical Protection
By: Eng.Mahmoud Mostafa Aiad- S.O.P.C
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Course components:
:
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:
.1Normal:()
.
.2Fault:.
.3Relay:
(Abnormal).
.4Contact)Open(NormallyNOC:
.
.5Contact)Closed(NormallyNOC:
. .6RelaysPrimary
:
.
.7RelaysSecondary:
.
.8RelaysElectromagnetic:
.
.9Static Relays:
(Slave devices)
.
.10Main relays:
.
.11Backup Relays
:
.
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:
.12Selectivity:
.
.13Sensitivity:
.
.14timeOperating:
.
.15RelayInstantaneous:.
.16relaydelayTime:.
.17relayscurrentOver:
.
.18RelayTimeDefinite:.
.19relayTimeInverse:
(I.T=K).
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FrequencyCurrentVoltage
FrequencyCurrent
V I F
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:
FrequencyCurrentVolt FrequencyCurrent
Under Voltage
Over Voltage
Phase Sequence
Phase losses
Surge voltage
Under Current
Over Current
Short circuit
Earth fault
Current Direction
Un balance current
Under Frequency
Over Frequency
Harmonic frequencies
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:
Elements to be Protected:
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Protection system components:
:
Protection System
Sense
Interface
Action
PT CTPT CT
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:
:
.
.
.
.
.
Purpose of Protection System:
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:
P.T, C.T .
Relays.
Fuses.Circuit Breaker
.
Surge Arrestor .
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C.T & P.T
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(C.T, P.T:)
2) Current Transformer (CT)1) Potential Transformer (PT)
Voltage Ratio ErrorClass
Measurement
0.1%0.1
0.2%0.2
0.5%0.5
1.0%1
3%3
Protective
3%3P
6%6P
Current Ratio ErrorClass
0.1%0.1
0.2%0.2
0.5%0.5
1.0%1
3%3
5%5
1%5P
3%10P
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Potential Transformer (P.T):
:
1-
.
U.V relay
O.V. -2 .
3-
Voltage Transducer
4-20 mA DCS.
:
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P.T types:
-:
-:
1) TransformerElectromagnetic Voltage
66.
Capacitor Voltage Transformer (2
66
(8)
:-
C2 -1 C1 . . ((reactor -2
P.Tintermediate -3
.
:
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Capacitor voltage Transformer:
:
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How to choose P.T?
:-
-:
Rated Transformation Ratio-1
.
s
pn
V
VK
:
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Ratio Error or Voltage Error -:2
=Kn
=V
p
=Vs
3:- Accuracy Class
((3
.
(4)
.
%p
ssnE
V
VVKR
How to choose P.T?
:
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(VA)burden -:4
VA
Voltage Error- Ratio Error
.
(5)
VA
VA .
VA25 - 35 - 45 80-100 .
How to choose P.T?
:
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VA
VAEquipment
5 VAVoltmeter
5 VAVoltage coil of wattmeter
7.5 VAVoltage coil of KWH meter
15 VAVoltage coil of synchroscope
5 VAUnder/Over voltage Relay
3-10 VAVoltage coil of electromagnetic relay0.02-0.2 VAStatic relays
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3Un/Insulation Voltage -5
Un Over Voltage
:-
-1
Un/3
-2
Um
100-110 V
Impulse Voltage
2 KV .
.
.13
5.2 KvUn
Um
How to choose P.T?
:
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:
(2PT) connection (3 PT) connection
Potential Transformer Connection:
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Current Transformer:
:
.1
()
5A & 1A
.
2..
3.
5A & 1ACurrent Transducer
(4-20 mA)
DCS.
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Shapes of Current Transformer:
:
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Current Transformer construction:
:
:
(cast resin)
( cast resin bar primary current transformer ) :-
. -1 -2
. -3
.. -4
(1)
:-
1- .( Double Terminal)
.
2- (Primary winding).
.
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( ( cast resin body -3
. 4- (soft magnetic core)
.
5- (secondary winding)
15
Ith6-
( Earthing screw of secondary)
S1
.7-
(secondary terminal)
Current Transformer construction:
:
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:
:-
:-Rated Transformations Ratio
(Name Plate).
.
=Isec.
=Ipr.
=K
.sec
.
I
IKn
pr
How to choose a C.T?
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:Ratio Error 3-2
(actual value) .
:
1- .
(short circuit) -2 .
3-3-
:Composite Error
(KnIsec.-Ipr.)(One Cycle)
Steady Condition
. r.m.s
2.5-5-7.5-10-15-30-40-VA
dtIIK
I
rrorCompositeE prnpr
)(100
.sec.
:
How to choose a C.T?
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3-4:- -Accuracy Class :
.
5P10
.
(3)
Class Curves
. -:3-5
(VA)Rated burden
VA
.
.
burden
((1
VA
.
.
((2
VA 10.
:
How to choose a C.T?
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-:Insulation Voltage -:3-6
(/3)
Um
Over voltage.
:-
1-
Un/3. -2
Um.
Impulse Volt
2KV
.
.13
*5.2 KvU
Un
n
:
How to choose a C.T?
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-:3-7Rated Thermal Current
r.m.s
(Short Circuited)
.
:-
1- .
2- ( . )
.
)Ith ) = 180 * S
)Ith ) = 118 * S
=S
:-
=Ith
t=Ith,t
T
II
thth t ,
:
How to choose a C.T?
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:
How to choose a C.T?
-:3-8
:-dynIRated dynamic Current
r.m.s
(Short Circuited)
:-
Idyn = 2.5 Ith .
Idyn Ith
.
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C.T Curve:
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:
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Current Transformer Connection:
:
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:
:Relays
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. :
- (
.)
- .
-
.
- .
Relays::
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: 1. Electromagnetic relays
{EMRs consist of an input coil that's wound to accept a particular voltage signal,plus a set of one or more contacts that rely on an armature (or lever) activated bythe energized coil to open or close an electrical circuit}.
2. Solid-State Relays{SSRs use semiconductor output instead of mechanical contacts to switch thecircuit. The output device is optically-coupled to an LED light source inside therelay. The relay is turned on by energizing this LED, usually with low-voltage DCpower}.
3. Micro Processor Based Relays
{Use microprocessor for switching mechanism. Commonly used in power systemmonitoring and protection}.
Relays:
:
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: .1
(Thermal relays.)
2. (Electromagnetic Attracted - Relays.)
3. (Electromagnetic Induction Relays.)
.4 (Static Relays.)
Relays:
:
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Relays:
:
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Induction type relay
Relays:
:
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Fuses:
:
:
( )
:Fuse)
( ) (
.)
.
()
.
( .)
()
.
(
cutout fuse.)
http://www.arab-eng.org/wiki/%D9%84%D8%BA%D8%A9_%D8%A5%D9%86%D8%AC%D9%84%D9%8A%D8%B2%D9%8A%D8%A9http://www.arab-eng.org/wiki/%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A1http://www.arab-eng.org/w/index.php?title=%D8%A5%D9%84%D9%83%D8%AA%D8%B1%D9%88%D9%86%D9%8A%D9%83&action=edit&redlink=1http://www.arab-eng.org/wiki/%D8%AA%D9%8A%D8%A7%D8%B1_%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8Ahttp://www.arab-eng.org/wiki/%D8%AA%D9%8A%D8%A7%D8%B1_%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8Ahttp://www.arab-eng.org/wiki/%D8%AF%D8%A7%D8%A6%D8%B1%D8%A9_%D9%82%D8%B5%D8%B1http://www.arab-eng.org/w/index.php?title=%D8%AD%D9%85%D9%88%D9%84%D8%A9_%D8%B2%D8%A7%D8%A6%D8%AF%D8%A9&action=edit&redlink=1http://www.arab-eng.org/w/index.php?title=%D8%A7%D9%84%D8%AD%D9%85%D8%A7%D9%8A%D8%A9_%D8%A7%D9%84%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8A%D8%A9&action=edit&redlink=1http://www.arab-eng.org/w/index.php?title=%D8%A7%D9%84%D8%AD%D9%85%D8%A7%D9%8A%D8%A9_%D8%A7%D9%84%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8A%D8%A9&action=edit&redlink=1http://www.arab-eng.org/w/index.php?title=%D8%AD%D9%85%D9%88%D9%84%D8%A9_%D8%B2%D8%A7%D8%A6%D8%AF%D8%A9&action=edit&redlink=1http://www.arab-eng.org/wiki/%D8%AF%D8%A7%D8%A6%D8%B1%D8%A9_%D9%82%D8%B5%D8%B1http://www.arab-eng.org/wiki/%D8%AA%D9%8A%D8%A7%D8%B1_%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8Ahttp://www.arab-eng.org/wiki/%D8%AA%D9%8A%D8%A7%D8%B1_%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A6%D9%8Ahttp://www.arab-eng.org/w/index.php?title=%D8%A5%D9%84%D9%83%D8%AA%D8%B1%D9%88%D9%86%D9%8A%D9%83&action=edit&redlink=1http://www.arab-eng.org/wiki/%D9%83%D9%87%D8%B1%D8%A8%D8%A7%D8%A1http://www.arab-eng.org/wiki/%D9%84%D8%BA%D8%A9_%D8%A5%D9%86%D8%AC%D9%84%D9%8A%D8%B2%D9%8A%D8%A98/3/2019 Electrical Protection By MMY
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Fuses:
:
:
() .
(weak point)
.
(1920)
M)(1930))
.
(1940).
IEC 60269
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Fuses:
:IEC 60269
(1950)
.
(/
).
.
.
.
.
:
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Fuses:
:
:((Fuse
:
.
:
2015
.
.:
.
110%
(Transient Recovery Voltage)
.
Capacity)(Interruption:
.
:
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Fuses:
:
:Fuse holder -1Fuse base -2Fuse carrier -3Fuse link -4
.
.
::((Fuse Link
Cartridge
arc-extinguishing
.
.
Fuse link.
element.
.
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:
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Fuses:
:
-(Rating Current):
Fuse link.
element.
-(:(minimum fusing current
Fuse element
.
asymptotic/
.
:((Fusing factor -
: =
:( ( Prearcing time -
.
:( ( arcing time -.
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:((Fuse operation time-/)
)
.
:
+=-
(Prospective Current):
(/
).
.(:(virtual time -
(). steady current
:
i.dt / Iptv =
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: 1.
.
2.
.
3. (recovery voltage. )
.4
.
.5
.
.
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: .1
5%
fusing factor(1.75)
(1.25).
.((1.252.
.
3.
.
4..5.
.
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: -
:
(:(Power Filled Fuses .1
.
( :(Miniature Fuses .2
. 3. (Semi-enclosed Fuses:)
.4(Expulsion Fuses):
:((Power Fuses.5
.Liquid quenched fuses .6(Distribution Break Fuses):
.
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- :.660 .1.660 .2-
:
.1 (Non-Current Limiting Fuses).
.
: .((Expulsion Fuses -.((Vacuum Fuses -
.2 (Current Limiting Fuses).
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(:(Expulsion Fuses -
. .
(K5000-4000)
. .
Pole-Mounted Transformers 3000 .
.
.
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(:(Vacuum Fuses -
.
.
.
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.2 (Current Limiting Fuses:)
Prospective Peak Current (1.) (ID)
Cut-Off Current
.
.
(.(It
.
(High Rupturing Capacity HRC-
Fuses).
(
. )
.
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: -
over load
short circuit
.
weak point
.
(4)
(4-)
Tin wire( fuse
link) .
. )-(4
semi enclosed rewirable fuses
.
(4-) insert open tube(4-)
.
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(-(4(Domestic (D) Type (D (-(5NH
miniature fuse
link semi conductor fuse links.(:(Fuses Design -
.
fuse element
.
:
.
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: -1Powder filled cartridge fuses
Powder quartz Silicon oxide (Si O2 .(
iron compounds
organic matter .
(5) Sand filled cartridge fuse
(100) .
:
()
Closing
angle.
Cut-Off current
(5000) =17300 Amp]([2)2x5000
.
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(1000).
. (5000)
.
((It Joule integral
(It.)
Constriction
.
Pre-arcing time
. .
. element .
filler ( )
. .
.tape wire
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Constriction( ) .
(6)
.
(1) (M)M-effect
(2)
.
(1)
.
(5) Dual element time lag.
Uniform element.
. :
(.(It
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Small over current .
.
.
(M)M-effect .
Low melting point alloy
. .
:
-
.
.
Constricted points
(It)
.
.
.
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:
:
. .
.
:
(.)..
Negative sequence current
.
.
.
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:
: .1
(Short circuit.) 2.
(.(Over Load (.(Locked Rotor 3.(.(Unbalanced Power Supply 4.(.(Under Voltage 5. 6.
(Under Current.)
.7 (Phase Reversal.)
.8 (Over current.)
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Power Transformer Protection:
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:
: .1
(Short circuit.)
. 2.
Power Transformer Protection:
1 Earth Fault protection:
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1-Earth Fault protection:
( .)
Y:
.
:
Y.
1. :
2 Differential Protection:
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2.Differential Protection:
2.
:
Differential protection of a Delta/Star transformer
2 Differential Protection:
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(
)
()
.
2.Differential Protection:
2.
:
3 Buchloz Relay:
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3.Buchloz Relay::.3
.
..
.
What make Buchloz relay Works?
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What make Buchloz relay Works?
:
(
)
.
.
.
.
.
.
Buchloz Relay
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Buchloz Relay
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Location of the Buchholz relay on the transformer
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Location of the Buchholz relay on the transformer
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4 Di l t t t th t
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4. Dial-type contact thermometer
.
.
.
(
).
4 Di l t t t th t
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4. Dial-type contact thermometer
5. Winding Temperature Indicator
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g p
.5
6. Magnetic oil-level indicator
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g
.
(limit position switch) .
.
6.
7. Magnetic oil-level indicator
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7. Magnetic oil level indicator
7.
8. Pressure relief
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8 essu e e e
Pressure Relief During Fault Pressure Relief Before FaultOccurrence
Pressure Relief During Fault Pressure Relief Before FaultOccurrence
.8
. Dehydrating Breather9
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.9
.
.
.
y g
. Dehydrating Breather9
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.9
y g
Generator Protection:
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:
.1
(Differential protection.)87G
.2 (Ground Fault for stator.)51G,64
.3 (Ground Fault for Rotor.)58
4.(Power Reverse.)32
5.
(Over Current.)51 V
6.(Under frequency.)81
7.(Over frequency.)81
8.(Over Voltage.)59
9.(Under voltage.)27
Generator Protection:
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10.(Unbalanced Load.)
11.(Winding Temperature).26
(Loss of Excitation.)40 12.
13.(Over Excitation.)24
14.(Over Load RTD.)49R
:
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1.
:
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2. :
3. Power Reverse (Anti-Motoring):
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.3:
( g)
4.Under/Over Frequency
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.4/ :
/ q y
4.Under/Over Voltage:
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.4/ :
g
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