SlideShare ist ein Scribd-Unternehmen logo
1 von 56
Downloaden Sie, um offline zu lesen
02/04/15
Dr.Latif Shaikh
 Introduction
 Circuit Breaker
 The Arc
 Isolators
 Air Circuit Breakers
 Air Blast Circuit Breakers
 Vacuum Circuit Breakers
 Oil Circuit Breakers
 Sulfur Hexafluoride Circuit Breakers
 Circuit Breaker Ratings
 Circuit Breaker Controls
 High Voltage Circuit Breakers Comparison
 Reclosures
 Sectionalizers
 Fuses
 Fuse application
02/04/15Dr.Latif Shaikh
 A circuit breaker is a piece of equipment which
can Make or break a circuit either manually or by
remote control under normal conditions.
 Break a circuit automatically under fault condition
 Make a circuit either manually or by remote under
fault condition
02/04/15Dr.Latif Shaikh
 CB consists of fixed and moving contacts called
electrodes
 Under normal operating condition these contacts
remain closed and will not open automatically
unless the system becomes faulty .These contacts
can be opened manually or by remote control.
 When a fault occurs in a circuit the trip coils of the
circuit breaker get energised and the moving
contacts are pulled apart by some mechanism
,thus opening the circuit.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
When contacts of circuit breaker starts separating the
contact resistance starts increasing. This increases the (I
square r) loss which is heat produced .
This heat increases the energy of electrons in the contact
areas and the ionized particles tries to maintain the
current when contacts are separated.This flow of
charged particles form one contact to other is called
an arc .
The medium surrounding the arc also contains ions .
Due to this charged particles the arc continues even if the
breakers contacts are separated.
The voltage (potential gradient) across the arc is less and
so it continues even for low voltages.
02/04/15Dr.Latif Shaikh
 DC arcs are to be interrupted by increasing the
resistance interruption method in which resistance of the
arc is increased so that the arc voltage can no longer
maintain the current and the arc is extinguished.
 Size of DC circuit breaker increases as the voltage level
increases.
 AC arcs current reduces to zero in each cycle (2 times)
 If the circuit breaker contacts are opened at time when
the current passed through zero and dielectric strength of
the medium is build up rapidly so that arc cannot strike
again then arc can be extinguished successfully.
 Size of AC circuit breaker can be small compared to
same voltage DC circuit breaker.
02/04/15Dr.Latif Shaikh
 Separate the contacts of circuit breaker such that
the arc resistance increases to a very high value.
The pd between the contacts is unable to
maintain the arc current. For high voltage circuit
breakers this method is impracticable since a
separation of many meters will be required.(High
Resistance Method)
 The ionized particles between the contacts tend
to maintain the arc. If the arc path is deionized
,the arc extinction is facilitated .This may be
achieved by cooling the arc or by bodily
removing the ionized particles from the space
between the contacts.(Low Resistance Method)
02/04/15Dr.Latif Shaikh
 Arc Voltage – It is the voltage that appears across the
contacts of the circuit breakers during the arcing
period as the contacts are opened.
 Recovery voltage – It is the normal frequency voltage
that appears across the contacts of circuit breaker
after final arc extinction.
 Rate of rise of restriking voltage – (RRRV) It is the rate
of increase of restriking voltage .RRRV depends upon
1) recovery voltage and 2) Natural frequency of
oscillation
02/04/15Dr.Latif Shaikh
 It is the transient
voltage that appears
across the contacts at
or near current zero
during arcing period.
 If dielectric strength rise
is greater than the rise
of restriking voltage
then the arc will not
restrike.
02/04/15Dr.Latif Shaikh
 It is the phenomena of current interruption before
natural current zero is reached. It occurs in air blast
circuit breaker because they retain same
extinguishing power irrespective of the magnitude
of current to be interrupted.
 When interrupting low inductive current
e.g.magnetising current of transformer, a rapid
deionizing effect causes current , to fall below its
zero value before natural current zero is called
current chopping.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
The switching Resistor (R) is connected in parallel with the
CB contacts. Current chopping produces high voltage
oscillations which can be prevented by this method.
During arc interruption CB contacts separate first and after
arc gets extinguished ‘S’ opens depending upon the
time delay provided to it.
When the fault occurs the CB contacts open and arc is
struck between them. Since R is in parallel with Cb
contacts ,a part of arc current flows through this
resistance so arc current decreases and deionization
rate increases. The arc resistance also increases so
current through R increases. This continue till the arc
current is insufficient to maintain the arc.
02/04/15Dr.Latif Shaikh
 Breaking capacity – It is the current (r.m.s.) that a Cb
is capable of breaking at given recovery voltage and
under specified conditions.
 Making Capacity – The peak value of current
(including DC component) during the first cycle of
current wave after closure of circuit breaker is known
as making capacity. Making capacity = 2.55 ×
symmetrical breaking capacity
 Short time rating – It is the period for which the CB is
able to carry fault current while remaining closed.
 Normal current rating – It is the r.m.s. value of current
which the CB is capable of carrying continuously at its
rated frequency under rated specified conditions.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
1.Air Circuit Breakers
2.Air Blast Circuit Breakers
3. Vacuum Circuit Breakers
4.Oil Circuit Breakers
5.Sulfur hexafluoride circuit breakers
02/04/15Dr.Latif Shaikh
1.In this Circuit Breaker the arc is elongated using arc
runners and arc splitters so as to increase the
resistance of the arc.
3.This increases the voltage required to maintain the
arc and if the available voltage cannot sustain the
arc ,the arc gets extinguished.
2.At current zero ,the recovery voltage across the
contacts becomes less than the arc voltage and
the arc gets extinguished.
4. The energy in the system inductance at current
zero is zero .Hence arc interruption is easier.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
 1 Main contacts
 2 Arcing Contacts
 3.Arc Rising in the direction of Arrow
 4.Arc getting Split
 5.Arc Splitter Plates
 6.Current Carrying Terminals
 7.Arc Runners
02/04/15Dr.Latif Shaikh
Air Circuit Breakers
1.Used For low voltage levels and current levels
2.As voltage level increases, the size of breaker
becomes large so not convenient for higher voltage
and current levels.
3.Air is used as medium to extinguish the arc which
have inferior extinguishing properties compared to
SF6 or Vacuum circuit breakers
4.Operating control is manual as well as automatic.
5.It is used up to 6.6kV with a breaking capacity of
15MVA.
6.Suitable for repeated operation because medium of
arc extinction is air.
02/04/15Dr.Latif Shaikh
In this breaker, a high pressure air blast is used
as an arc quenching medium.
The contacts are opened and a flow of air blast
is maintained by opening the blast valve.
The air blast cools the arc and takes away the
arcing products to atmosphere .
This rapidly increases the dielectric strength of
the medium between the contacts and the arc
is extinguished and the flow of current is
interrupted.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
 High speed of operation
 Short arcing time
 High speed reclosing
 Less weigh as compared to oil circuit breakers
 Very less maintenance
 No possibility of explosion
 Cost is more
 For complete compress air installation is
required
 These breakers are more sensitive to RRRV.
 For operation and maintenance ,highly
skilled persons are required
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
Air is admitted in the arc extinction chamber it pushes
the moving contact. This air blast takes away the
ionized gases along with it. Afterwards the arc gets
extinguished. High pressure air has higher dielectric
strength.
The design is such that the air expands into the low
pressure (atmospheric pressure zone).The air at high
speed removes heat from the arc, thus arc is
quenched. Diameter of arc is reduced.
Uses
1.Arc Furnaces
2.Traction Syetems
02/04/15Dr.Latif Shaikh
When two contactsof thiscircuit breaker areseparated in
vacuum an arc isstruck and hot spotsareformed on thesurface
of thecontacts.Thesehot spotsproducemetal vapor and plasma.
Theamount of vapor in plasmadependson how rapidly the
vapor isemitted from contact surfacewhich dependson thearc
current. Thecurrent isof alternating nature, it passthrough zero
several times, so therateof vapor emission also becomeszero,
and thevapor already emitted getscondensed . During this
processthedielectric strength buildsup rapidly and the
restriking of arc isprevented.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
It consists of fixed contact, moving contact and arc
shield mounted inside a vacuum chamber. The
movable member is connected to the control
mechanism by stainless steel bellows. This enables the
permanent sealing of the vacuum chamber so as to
eliminate the possibility of leakage,.
A glass vessel or ceramic vessel is used as outer
insulating body. The arc shield prevents the
deterioration of the internal dielectric strength by
preventing the deterioration of the internal dielectric
strength.
Applications –
Outdoor application where maintenance required is
minimum.In the high voltage system from 22 KV to
66kV power Circuits.
02/04/15Dr.Latif Shaikh
When two contacts of circuit breaker are separated in
vacuum arc is struck and hot spots are formed on
the surface of the contacts. These hot spots
produce metal vapour and plasma.
At current zero the rate of vapour emission becomes
zero.
The vapour already emitted gets condensed .
During this process the dielectric strength builds up and
the restriking of arc is prevented.
02/04/15Dr.Latif Shaikh
 Compact in size
 Reliable and long life
 Heavy fault can be interrupted effectively
 No gas is generated after arc extinction
operation
 Operation is not noisy
 Arc energy is low
 No risk of fire
 Vacuum has to be maintained at desired
level always
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
This breaker makes use of oil for quenching the arc.
The circuit breaker which uses more oil or which is
bulky is called bulk oil circuit breaker.
The construction is simple and it consists of fixed and
moving contacts enclosed in a strong weather –
tight earthed tank containing oil up to a certain
level and an air cushion above the oil level.
Application
These breakers are used up to 11 KV with an
interrupting capacity of 250MVA.
02/04/15Dr.Latif Shaikh
Under normal working conditions, thefixed and moving contactsare
closed. On theoccurrenceof fault, themoving contactscomedown
and an arc isstruck between thecontacts. Theoil between the
contactsgetsdecomposed and hydrogen gasbubbleisformed
around thecontacts. Thehydrogen gascoolsthearc and the
turbulenceeffect causethelengthening of arc. Thedeionization of
medium between contactstakesplaceand at somecritical length of
gap between thecontacts,thearc isextinguished.
Thehydrogen gasbubbleproducesavery high pressurein theoil. The
tank isthereforemadestrong to withstand alargepressure. Theoil
movesupwardswhen hydrogen bubbleisformed. Theair ispresent
between theoil level and tank top and actsascushion and absorbs
mechanical shock produced dueto upward oil movement.
02/04/15Dr.Latif Shaikh
 oil has high dielectric strength
 Oil absorbs arc energy while
decomposing
 Good cooling property of the gas formed
due to decomposition
 It acts as an insulator between the live
parts and earth
 Long arcing time
 Do not permit high speed of interruption
 Arc interruption control can be obtained
only by increasing the length of arc
 Chance of fire and explosion.
02/04/15Dr.Latif Shaikh
 Operation
 When the contacts are
separated in oil arc is
formed. The heat of arc
decomposes oil and
gases are formed. These
gases expand due to
heating of the arc. The
gas flowing near the
contact zone cause
cooling and splitting of
the arc and the arc gets
extinguished.
02/04/15Dr.Latif Shaikh
In this breaker, the supporting ,current interruption and
top chamber are made of porcelain .Hence,
clearance between live parts is small and requires
less quantity of oil, hence the breaker is called
Minimum Oil Circuit Breaker. The chambers are
completely filled with oil. The oil from upper
chamber does not come to lower.
The fixed contact is enclosed in the quenching
chamber. Moving contact makes sliding contact
with the lower fixed contact. The operating rod is
operated by operating mechanism, the three poles
operate simultaneously.The voltage ratings are from
3.6kV to 420 KV.
02/04/15Dr.Latif Shaikh
 Requires less quantity of oil
 Requires smaller space
 Maintenance is less
 Cost per breaking capacity in MVA is less
 Suitable for both manual and automatic
operation
 Possibility of fire and explosion.
 Difficult to remove gases from the space
between contacts.
 Oil deteriorates rapidly due to
carbonization
 Smaller quantity of oil, so carbonization
increases.
02/04/15Dr.Latif Shaikh
 Electronegative –It has the ability of an atom to attract
and hold electrons. Such gas have high dielectric
stremngth.SF6 is electronegative .It forms negative
ions ,Negative ions are heavy and immobile so they do
not flow easily .Hence SF6 gas has high dielectric
strength.
 Rate of rise of dielectric strength is very high.
 Can be liquefied and stored in steel tanks
 Dielectric strength increase linearly with pressure.
 Gas is inert. Therefore contacts will not get eroded.
 Gas is non –inflammable , Colorless ,odorless, Non-toxic
 Thermally stable up to 55 degrees
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
 Under normal operating conditions the contacts are closed .
 On occurance of fault contacts are opened. The movable
contact moves away from the fixed contact.
 The arc is struck between the fixed and moving contacts.
 High pressure SF6 gas now flows over the arc and it absorbs
the free electrons from the arc.
 This builds up the dielectric strength between the gap very
fast and the arc is extinguished
02/04/15Dr.Latif Shaikh
Advantages
 Silent operation, compact
size
 Vary short arcing time
 No risk of fire
 No reduction in dielectric
strength due to operation
 No moisture problem
 No current chopping
problem
 Can interrupt larger
currents
 Suitable for explosive
environment due to
totally enclosed body
Disadvantages
 Costly
 Requires conditioning of SF6
gas from time to time
 SF6 gas is suffocating ,so its
leakage can cause
suffovcation of the persons
in surrounding areas.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
Isolator(disconnecting switch) operates under no
load condition. It does not have any current
breaking capacity or current making capacity.
Isolator is not even used for breaking load currents.
Isolators are used in addition to circuit breakers ,and
are provided on each side of every circuit breaker
to provide isolation and enable maintenance.
Sequence of operation
While opening –Open circuit breaker first and then
isolators
While closing –Close isolators first and then close
circuit breakers
02/04/15Dr.Latif Shaikh
Different types of controls are required for successful operation
of circuit breakers.
1.Relays – These are required to give a trip signal to circuit
breaker in case of fault condition. Different types of relays are
available like over current, over voltage ,under voltage, loss
of excitation,reverse power etc.
2.Sensor equipments are required to check the condition of
circuit breakers arc extinguishing medium .
The controls are pressure sensors to sense the pressure of air in
case of air blast circuit breakers .
In case of Sulfur hexafluoride circuit breakers also the pressure
sensors are required.
In case of vacuum circuit breakers also sensors are required to
check the vacuum level in the breaker.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
 The faults in power system may be temporary or
permanent.
 The temporary faults like touching of overhead
conductors due to wind are cleared automatically
after some time .
 In case of temporary faults auto reclosing helps to
maintain the system supply .
 The breaker opens on a fault.
 After some time delay ,the breaker is closed .
 If the fault is temporary and it is removed ,then the
breaker will close successfully
 If the fault still persists then the breaker opens.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
Sectionalizers are used in the bus bars so that fault on any
section of bus bar will not cause complete shut down.
Advantages of sectionalizers
1.If fault occurs on any section of bus bars then that section
is isolated from other sections without affecting the
system.
2.Fault current is much lower than in case of un
sectionalized system (as the fault is fed from only one
section)
3.Repairing and maintenance on one section can be
carried out by de energizing that section only
eliminating the possibility of complete shut down.
The breaker in the bus bars is acting as sectionalizing
breaker in the shown figure.
02/04/15Dr.Latif Shaikh
Fuse is a device used in circuit for protecting electrical
equipments against overloads and /or short circuits.
Fuse element or fuse wire is that part of the fuse device
which melts when an excessive current flows in the
circuit and thus isolates the faulty device from the
supply circuit.
Desirable qualities of fuse elements
1.Low melting point
2.Low ohmic losses
3.High conductivity
4.Free from deterioration due to oxidation
5.Low cost
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh
It consists of a heat resisting ceramic body having
metal end caps. A fusible wire is welded to it. The
space within the body, surrounding the element is
completely packed with a powder, usually quartz,
which acts as an arc extinguishing medium.
Under fault condition, the current flowing through the
element produces very large amount heat and the
fuse element melts before the fault current reaches
first peak value. The heat produced in the process
vaporizes the melted fuse element. The chemical
reaction between the silver vapor and filling power
results in the formation of high resistance which
helps quenching the arc.
02/04/15Dr.Latif Shaikh
02/04/15Dr.Latif Shaikh

Weitere ähnliche Inhalte

Was ist angesagt?

Lightning Arrester Working Principle & Types
Lightning Arrester Working Principle & TypesLightning Arrester Working Principle & Types
Lightning Arrester Working Principle & TypesPower System Operation
 
Air circuit breakers
Air circuit breakersAir circuit breakers
Air circuit breakersPrasant Kumar
 
Vacuum circuit breaker
Vacuum circuit breakerVacuum circuit breaker
Vacuum circuit breakeropjit88
 
ABCB(air blast circuit breaker)
ABCB(air blast circuit breaker)ABCB(air blast circuit breaker)
ABCB(air blast circuit breaker)AB Amit
 
Power Transformer Protection
Power Transformer ProtectionPower Transformer Protection
Power Transformer ProtectionAng Sovann
 
**Lightning Arrester Presentation**
**Lightning Arrester Presentation****Lightning Arrester Presentation**
**Lightning Arrester Presentation**SKPAMB
 
Switchgear and protection 1
Switchgear and protection 1Switchgear and protection 1
Switchgear and protection 1Md Irshad Ahmad
 
Switchgear - complete guide
Switchgear - complete guideSwitchgear - complete guide
Switchgear - complete guideSlides Hub
 
Switchgear and protection lecture 2 type of circuit breakers and applications
Switchgear and protection lecture 2 type of circuit breakers and applicationsSwitchgear and protection lecture 2 type of circuit breakers and applications
Switchgear and protection lecture 2 type of circuit breakers and applicationsanuphowlader1
 
Ppt on protection of power transformers
Ppt on protection of power transformersPpt on protection of power transformers
Ppt on protection of power transformerssiddharam kantoli
 
Circuit Breaker : Types
Circuit Breaker : TypesCircuit Breaker : Types
Circuit Breaker : TypesRidwanul Hoque
 
Substation protection devices
Substation protection devicesSubstation protection devices
Substation protection devicesRahul Aman
 
Protective relay
Protective relay Protective relay
Protective relay Uday Wankar
 
Unit 03 Protective relays
Unit  03 Protective relaysUnit  03 Protective relays
Unit 03 Protective relaysPremanandDesai
 
Surge arrester ppt
Surge arrester pptSurge arrester ppt
Surge arrester pptIrinElsa
 
Switchgear Equipment in a Substation
Switchgear Equipment in a SubstationSwitchgear Equipment in a Substation
Switchgear Equipment in a SubstationMd. Atiqur Rahman
 

Was ist angesagt? (20)

Circuit breaker
Circuit breakerCircuit breaker
Circuit breaker
 
Circuit Breakers
Circuit BreakersCircuit Breakers
Circuit Breakers
 
Lightning Arrester Working Principle & Types
Lightning Arrester Working Principle & TypesLightning Arrester Working Principle & Types
Lightning Arrester Working Principle & Types
 
Air circuit breakers
Air circuit breakersAir circuit breakers
Air circuit breakers
 
Vacuum circuit breaker
Vacuum circuit breakerVacuum circuit breaker
Vacuum circuit breaker
 
ABCB(air blast circuit breaker)
ABCB(air blast circuit breaker)ABCB(air blast circuit breaker)
ABCB(air blast circuit breaker)
 
Power Transformer Protection
Power Transformer ProtectionPower Transformer Protection
Power Transformer Protection
 
**Lightning Arrester Presentation**
**Lightning Arrester Presentation****Lightning Arrester Presentation**
**Lightning Arrester Presentation**
 
Switchgear and protection 1
Switchgear and protection 1Switchgear and protection 1
Switchgear and protection 1
 
Switchgear - complete guide
Switchgear - complete guideSwitchgear - complete guide
Switchgear - complete guide
 
Switchgear and protection lecture 2 type of circuit breakers and applications
Switchgear and protection lecture 2 type of circuit breakers and applicationsSwitchgear and protection lecture 2 type of circuit breakers and applications
Switchgear and protection lecture 2 type of circuit breakers and applications
 
Ppt on protection of power transformers
Ppt on protection of power transformersPpt on protection of power transformers
Ppt on protection of power transformers
 
Circuit Breaker : Types
Circuit Breaker : TypesCircuit Breaker : Types
Circuit Breaker : Types
 
Substation protection devices
Substation protection devicesSubstation protection devices
Substation protection devices
 
Protective relay
Protective relay Protective relay
Protective relay
 
Unit 03 Protective relays
Unit  03 Protective relaysUnit  03 Protective relays
Unit 03 Protective relays
 
Lightning arrester
Lightning arresterLightning arrester
Lightning arrester
 
Surge arrester ppt
Surge arrester pptSurge arrester ppt
Surge arrester ppt
 
Switchgear Equipment in a Substation
Switchgear Equipment in a SubstationSwitchgear Equipment in a Substation
Switchgear Equipment in a Substation
 
Overcurrent Protection
Overcurrent ProtectionOvercurrent Protection
Overcurrent Protection
 

Andere mochten auch

Andere mochten auch (8)

Oil circuit breakers
Oil circuit breakersOil circuit breakers
Oil circuit breakers
 
Bulk oil & Minimum oil Circuit Breakers
Bulk oil & Minimum oil Circuit BreakersBulk oil & Minimum oil Circuit Breakers
Bulk oil & Minimum oil Circuit Breakers
 
Oil Circuit Breaker(classification of circuit breakers)
Oil Circuit Breaker(classification of circuit breakers)Oil Circuit Breaker(classification of circuit breakers)
Oil Circuit Breaker(classification of circuit breakers)
 
Circuit breakers
Circuit breakersCircuit breakers
Circuit breakers
 
circuit breaker
circuit breakercircuit breaker
circuit breaker
 
Study of circuit breakers
Study of circuit breakersStudy of circuit breakers
Study of circuit breakers
 
Circuit breaker
Circuit breakerCircuit breaker
Circuit breaker
 
Circuit Breaker
Circuit BreakerCircuit Breaker
Circuit Breaker
 

Ähnlich wie Circuit Breakers

Relay and switchgear protection
Relay and switchgear protectionRelay and switchgear protection
Relay and switchgear protectionBinit Das
 
SGPD(MOD-4).pdf...................................................
SGPD(MOD-4).pdf...................................................SGPD(MOD-4).pdf...................................................
SGPD(MOD-4).pdf...................................................MANOJ KHARADE
 
SGPD(MOD-4).pdfsgp .....................
SGPD(MOD-4).pdfsgp .....................SGPD(MOD-4).pdfsgp .....................
SGPD(MOD-4).pdfsgp .....................MANOJ KHARADE
 
highvoltagecircuitbreakers-180415102549.pdf
highvoltagecircuitbreakers-180415102549.pdfhighvoltagecircuitbreakers-180415102549.pdf
highvoltagecircuitbreakers-180415102549.pdfNagsSuresh
 
High voltage circuit breakers
High voltage circuit breakersHigh voltage circuit breakers
High voltage circuit breakersKabilesh K
 
Circuitbreakers 140829234332-phpapp01
Circuitbreakers 140829234332-phpapp01Circuitbreakers 140829234332-phpapp01
Circuitbreakers 140829234332-phpapp01rana usman
 
Air Blast & SF6 Circuit Breaker Design and Construction
Air Blast & SF6 Circuit Breaker Design and Construction Air Blast & SF6 Circuit Breaker Design and Construction
Air Blast & SF6 Circuit Breaker Design and Construction anuphowlader1
 
Switchgear and protection engineering Lecture 03.pptx
Switchgear and protection engineering Lecture 03.pptxSwitchgear and protection engineering Lecture 03.pptx
Switchgear and protection engineering Lecture 03.pptxLoitaFredy
 
Circuit breaker arc phenomena
Circuit breaker arc phenomenaCircuit breaker arc phenomena
Circuit breaker arc phenomenaBhavin Pradhan
 
protection circuits of scr.pptx
protection circuits of scr.pptxprotection circuits of scr.pptx
protection circuits of scr.pptxyogeshkute
 
PSG_unit3_motor protection.ppt
PSG_unit3_motor protection.pptPSG_unit3_motor protection.ppt
PSG_unit3_motor protection.pptRajaDesingu2
 

Ähnlich wie Circuit Breakers (20)

Relay and switchgear protection
Relay and switchgear protectionRelay and switchgear protection
Relay and switchgear protection
 
SGPD(MOD-4).pdf...................................................
SGPD(MOD-4).pdf...................................................SGPD(MOD-4).pdf...................................................
SGPD(MOD-4).pdf...................................................
 
SGPD(MOD-4).pdfsgp .....................
SGPD(MOD-4).pdfsgp .....................SGPD(MOD-4).pdfsgp .....................
SGPD(MOD-4).pdfsgp .....................
 
highvoltagecircuitbreakers-180415102549.pdf
highvoltagecircuitbreakers-180415102549.pdfhighvoltagecircuitbreakers-180415102549.pdf
highvoltagecircuitbreakers-180415102549.pdf
 
High voltage circuit breakers
High voltage circuit breakersHigh voltage circuit breakers
High voltage circuit breakers
 
Circuit Breaker
Circuit BreakerCircuit Breaker
Circuit Breaker
 
Circuitbreakers 140829234332-phpapp01
Circuitbreakers 140829234332-phpapp01Circuitbreakers 140829234332-phpapp01
Circuitbreakers 140829234332-phpapp01
 
Circuit breakers
Circuit breakersCircuit breakers
Circuit breakers
 
Air Blast & SF6 Circuit Breaker Design and Construction
Air Blast & SF6 Circuit Breaker Design and Construction Air Blast & SF6 Circuit Breaker Design and Construction
Air Blast & SF6 Circuit Breaker Design and Construction
 
Circuit Breaker
Circuit BreakerCircuit Breaker
Circuit Breaker
 
Ciruit breaker
Ciruit breakerCiruit breaker
Ciruit breaker
 
Air Circuit breaker
Air Circuit breakerAir Circuit breaker
Air Circuit breaker
 
air type circuit breaker
air type circuit breakerair type circuit breaker
air type circuit breaker
 
Switchgear and protection engineering Lecture 03.pptx
Switchgear and protection engineering Lecture 03.pptxSwitchgear and protection engineering Lecture 03.pptx
Switchgear and protection engineering Lecture 03.pptx
 
Air break CB.pdf
Air break CB.pdfAir break CB.pdf
Air break CB.pdf
 
Circuit breaker arc phenomena
Circuit breaker arc phenomenaCircuit breaker arc phenomena
Circuit breaker arc phenomena
 
protection circuits of scr.pptx
protection circuits of scr.pptxprotection circuits of scr.pptx
protection circuits of scr.pptx
 
Lecture_14_Circuit_Breakers.pptx
Lecture_14_Circuit_Breakers.pptxLecture_14_Circuit_Breakers.pptx
Lecture_14_Circuit_Breakers.pptx
 
SGP_170993109001
SGP_170993109001SGP_170993109001
SGP_170993109001
 
PSG_unit3_motor protection.ppt
PSG_unit3_motor protection.pptPSG_unit3_motor protection.ppt
PSG_unit3_motor protection.ppt
 

Mehr von Ameen San

Application of Capacitors to Distribution System and Voltage Regulation
Application of Capacitors to Distribution System and Voltage RegulationApplication of Capacitors to Distribution System and Voltage Regulation
Application of Capacitors to Distribution System and Voltage RegulationAmeen San
 
Distribution System Voltage Drop and Power Loss Calculation
Distribution System Voltage Drop and Power Loss CalculationDistribution System Voltage Drop and Power Loss Calculation
Distribution System Voltage Drop and Power Loss CalculationAmeen San
 
Load Characteristics
Load CharacteristicsLoad Characteristics
Load CharacteristicsAmeen San
 
ELECTRICAL DISTRIBUTION TECHNOLOGY
ELECTRICAL DISTRIBUTION TECHNOLOGYELECTRICAL DISTRIBUTION TECHNOLOGY
ELECTRICAL DISTRIBUTION TECHNOLOGYAmeen San
 
Stepper motor
Stepper motor Stepper motor
Stepper motor Ameen San
 
PLC application
PLC applicationPLC application
PLC applicationAmeen San
 
PLC arithmatic functions
PLC arithmatic functionsPLC arithmatic functions
PLC arithmatic functionsAmeen San
 
PLC data types and addressing
PLC data types and addressingPLC data types and addressing
PLC data types and addressingAmeen San
 
PLC Counters
PLC CountersPLC Counters
PLC CountersAmeen San
 
PLC Traffic Light Control
PLC Traffic Light ControlPLC Traffic Light Control
PLC Traffic Light ControlAmeen San
 
PLC Internal Relays
PLC Internal RelaysPLC Internal Relays
PLC Internal RelaysAmeen San
 
PLC Intro to programming
PLC Intro to programmingPLC Intro to programming
PLC Intro to programmingAmeen San
 
PLC Logic Circuits
PLC Logic CircuitsPLC Logic Circuits
PLC Logic CircuitsAmeen San
 
PLC input and output devices
PLC input and output devices PLC input and output devices
PLC input and output devices Ameen San
 
PLC Applications
PLC ApplicationsPLC Applications
PLC ApplicationsAmeen San
 
Protection Devices and the Lightning
Protection Devices and the LightningProtection Devices and the Lightning
Protection Devices and the LightningAmeen San
 
Engineering Economy
Engineering EconomyEngineering Economy
Engineering EconomyAmeen San
 

Mehr von Ameen San (20)

Application of Capacitors to Distribution System and Voltage Regulation
Application of Capacitors to Distribution System and Voltage RegulationApplication of Capacitors to Distribution System and Voltage Regulation
Application of Capacitors to Distribution System and Voltage Regulation
 
Distribution System Voltage Drop and Power Loss Calculation
Distribution System Voltage Drop and Power Loss CalculationDistribution System Voltage Drop and Power Loss Calculation
Distribution System Voltage Drop and Power Loss Calculation
 
Load Characteristics
Load CharacteristicsLoad Characteristics
Load Characteristics
 
ELECTRICAL DISTRIBUTION TECHNOLOGY
ELECTRICAL DISTRIBUTION TECHNOLOGYELECTRICAL DISTRIBUTION TECHNOLOGY
ELECTRICAL DISTRIBUTION TECHNOLOGY
 
Stepper motor
Stepper motor Stepper motor
Stepper motor
 
PLC application
PLC applicationPLC application
PLC application
 
PLC arithmatic functions
PLC arithmatic functionsPLC arithmatic functions
PLC arithmatic functions
 
PLC data types and addressing
PLC data types and addressingPLC data types and addressing
PLC data types and addressing
 
PLC Counters
PLC CountersPLC Counters
PLC Counters
 
PLC Traffic Light Control
PLC Traffic Light ControlPLC Traffic Light Control
PLC Traffic Light Control
 
PLC Timers
PLC TimersPLC Timers
PLC Timers
 
PLC Internal Relays
PLC Internal RelaysPLC Internal Relays
PLC Internal Relays
 
PLC Intro to programming
PLC Intro to programmingPLC Intro to programming
PLC Intro to programming
 
PLC Logic Circuits
PLC Logic CircuitsPLC Logic Circuits
PLC Logic Circuits
 
PLC input and output devices
PLC input and output devices PLC input and output devices
PLC input and output devices
 
PLC Applications
PLC ApplicationsPLC Applications
PLC Applications
 
Protection Devices and the Lightning
Protection Devices and the LightningProtection Devices and the Lightning
Protection Devices and the Lightning
 
Protection
ProtectionProtection
Protection
 
Relays
RelaysRelays
Relays
 
Engineering Economy
Engineering EconomyEngineering Economy
Engineering Economy
 

Kürzlich hochgeladen

Introduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHIntroduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHC Sai Kiran
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technologyabdulkadirmukarram03
 
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...soginsider
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxKISHAN KUMAR
 
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratoryدليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide LaboratoryBahzad5
 
Phase noise transfer functions.pptx
Phase noise transfer      functions.pptxPhase noise transfer      functions.pptx
Phase noise transfer functions.pptxSaiGouthamSunkara
 
CSR Managerial Round Questions and answers.pptx
CSR Managerial Round Questions and answers.pptxCSR Managerial Round Questions and answers.pptx
CSR Managerial Round Questions and answers.pptxssusera0771e
 
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.ppt
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.pptOracle_PLSQL_basic_tutorial_with_workon_Exercises.ppt
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.pptDheerajKashnyal
 
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxVertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxLMW Machine Tool Division
 
Technical Management of cement industry.pdf
Technical Management of cement industry.pdfTechnical Management of cement industry.pdf
Technical Management of cement industry.pdfMadan Karki
 
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...amrabdallah9
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxrealme6igamerr
 
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Apollo Techno Industries Pvt Ltd
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical SensorTanvir Moin
 
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfsdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfJulia Kaye
 
News web APP using NEWS API for web platform to enhancing user experience
News web APP using NEWS API for web platform to enhancing user experienceNews web APP using NEWS API for web platform to enhancing user experience
News web APP using NEWS API for web platform to enhancing user experienceAkashJha84
 

Kürzlich hochgeladen (20)

Introduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECHIntroduction to Machine Learning Unit-3 for II MECH
Introduction to Machine Learning Unit-3 for II MECH
 
The relationship between iot and communication technology
The relationship between iot and communication technologyThe relationship between iot and communication technology
The relationship between iot and communication technology
 
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...Transforming Process Safety Management: Challenges, Benefits, and Transition ...
Transforming Process Safety Management: Challenges, Benefits, and Transition ...
 
Mohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptxMohs Scale of Hardness, Hardness Scale.pptx
Mohs Scale of Hardness, Hardness Scale.pptx
 
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratoryدليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
دليل تجارب الاسفلت المختبرية - Asphalt Experiments Guide Laboratory
 
Litature Review: Research Paper work for Engineering
Litature Review: Research Paper work for EngineeringLitature Review: Research Paper work for Engineering
Litature Review: Research Paper work for Engineering
 
Phase noise transfer functions.pptx
Phase noise transfer      functions.pptxPhase noise transfer      functions.pptx
Phase noise transfer functions.pptx
 
CSR Managerial Round Questions and answers.pptx
CSR Managerial Round Questions and answers.pptxCSR Managerial Round Questions and answers.pptx
CSR Managerial Round Questions and answers.pptx
 
Présentation IIRB 2024 Marine Cordonnier.pdf
Présentation IIRB 2024 Marine Cordonnier.pdfPrésentation IIRB 2024 Marine Cordonnier.pdf
Présentation IIRB 2024 Marine Cordonnier.pdf
 
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.ppt
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.pptOracle_PLSQL_basic_tutorial_with_workon_Exercises.ppt
Oracle_PLSQL_basic_tutorial_with_workon_Exercises.ppt
 
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptxVertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
Vertical- Machining - Center - VMC -LMW-Machine-Tool-Division.pptx
 
Lecture 2 .pdf
Lecture 2                           .pdfLecture 2                           .pdf
Lecture 2 .pdf
 
Technical Management of cement industry.pdf
Technical Management of cement industry.pdfTechnical Management of cement industry.pdf
Technical Management of cement industry.pdf
 
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
Strategies of Urban Morphologyfor Improving Outdoor Thermal Comfort and Susta...
 
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptxUNIT4_ESD_wfffffggggggggggggith_ARM.pptx
UNIT4_ESD_wfffffggggggggggggith_ARM.pptx
 
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...Technology Features of Apollo HDD Machine, Its Technical Specification with C...
Technology Features of Apollo HDD Machine, Its Technical Specification with C...
 
Basic Principle of Electrochemical Sensor
Basic Principle of  Electrochemical SensorBasic Principle of  Electrochemical Sensor
Basic Principle of Electrochemical Sensor
 
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdfsdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
sdfsadopkjpiosufoiasdoifjasldkjfl a asldkjflaskdjflkjsdsdf
 
News web APP using NEWS API for web platform to enhancing user experience
News web APP using NEWS API for web platform to enhancing user experienceNews web APP using NEWS API for web platform to enhancing user experience
News web APP using NEWS API for web platform to enhancing user experience
 
Lecture 2 .pptx
Lecture 2                            .pptxLecture 2                            .pptx
Lecture 2 .pptx
 

Circuit Breakers

  • 2.  Introduction  Circuit Breaker  The Arc  Isolators  Air Circuit Breakers  Air Blast Circuit Breakers  Vacuum Circuit Breakers  Oil Circuit Breakers  Sulfur Hexafluoride Circuit Breakers  Circuit Breaker Ratings  Circuit Breaker Controls  High Voltage Circuit Breakers Comparison  Reclosures  Sectionalizers  Fuses  Fuse application 02/04/15Dr.Latif Shaikh
  • 3.  A circuit breaker is a piece of equipment which can Make or break a circuit either manually or by remote control under normal conditions.  Break a circuit automatically under fault condition  Make a circuit either manually or by remote under fault condition 02/04/15Dr.Latif Shaikh
  • 4.  CB consists of fixed and moving contacts called electrodes  Under normal operating condition these contacts remain closed and will not open automatically unless the system becomes faulty .These contacts can be opened manually or by remote control.  When a fault occurs in a circuit the trip coils of the circuit breaker get energised and the moving contacts are pulled apart by some mechanism ,thus opening the circuit. 02/04/15Dr.Latif Shaikh
  • 7. When contacts of circuit breaker starts separating the contact resistance starts increasing. This increases the (I square r) loss which is heat produced . This heat increases the energy of electrons in the contact areas and the ionized particles tries to maintain the current when contacts are separated.This flow of charged particles form one contact to other is called an arc . The medium surrounding the arc also contains ions . Due to this charged particles the arc continues even if the breakers contacts are separated. The voltage (potential gradient) across the arc is less and so it continues even for low voltages. 02/04/15Dr.Latif Shaikh
  • 8.  DC arcs are to be interrupted by increasing the resistance interruption method in which resistance of the arc is increased so that the arc voltage can no longer maintain the current and the arc is extinguished.  Size of DC circuit breaker increases as the voltage level increases.  AC arcs current reduces to zero in each cycle (2 times)  If the circuit breaker contacts are opened at time when the current passed through zero and dielectric strength of the medium is build up rapidly so that arc cannot strike again then arc can be extinguished successfully.  Size of AC circuit breaker can be small compared to same voltage DC circuit breaker. 02/04/15Dr.Latif Shaikh
  • 9.  Separate the contacts of circuit breaker such that the arc resistance increases to a very high value. The pd between the contacts is unable to maintain the arc current. For high voltage circuit breakers this method is impracticable since a separation of many meters will be required.(High Resistance Method)  The ionized particles between the contacts tend to maintain the arc. If the arc path is deionized ,the arc extinction is facilitated .This may be achieved by cooling the arc or by bodily removing the ionized particles from the space between the contacts.(Low Resistance Method) 02/04/15Dr.Latif Shaikh
  • 10.  Arc Voltage – It is the voltage that appears across the contacts of the circuit breakers during the arcing period as the contacts are opened.  Recovery voltage – It is the normal frequency voltage that appears across the contacts of circuit breaker after final arc extinction.  Rate of rise of restriking voltage – (RRRV) It is the rate of increase of restriking voltage .RRRV depends upon 1) recovery voltage and 2) Natural frequency of oscillation 02/04/15Dr.Latif Shaikh
  • 11.  It is the transient voltage that appears across the contacts at or near current zero during arcing period.  If dielectric strength rise is greater than the rise of restriking voltage then the arc will not restrike. 02/04/15Dr.Latif Shaikh
  • 12.  It is the phenomena of current interruption before natural current zero is reached. It occurs in air blast circuit breaker because they retain same extinguishing power irrespective of the magnitude of current to be interrupted.  When interrupting low inductive current e.g.magnetising current of transformer, a rapid deionizing effect causes current , to fall below its zero value before natural current zero is called current chopping. 02/04/15Dr.Latif Shaikh
  • 16. The switching Resistor (R) is connected in parallel with the CB contacts. Current chopping produces high voltage oscillations which can be prevented by this method. During arc interruption CB contacts separate first and after arc gets extinguished ‘S’ opens depending upon the time delay provided to it. When the fault occurs the CB contacts open and arc is struck between them. Since R is in parallel with Cb contacts ,a part of arc current flows through this resistance so arc current decreases and deionization rate increases. The arc resistance also increases so current through R increases. This continue till the arc current is insufficient to maintain the arc. 02/04/15Dr.Latif Shaikh
  • 17.  Breaking capacity – It is the current (r.m.s.) that a Cb is capable of breaking at given recovery voltage and under specified conditions.  Making Capacity – The peak value of current (including DC component) during the first cycle of current wave after closure of circuit breaker is known as making capacity. Making capacity = 2.55 × symmetrical breaking capacity  Short time rating – It is the period for which the CB is able to carry fault current while remaining closed.  Normal current rating – It is the r.m.s. value of current which the CB is capable of carrying continuously at its rated frequency under rated specified conditions. 02/04/15Dr.Latif Shaikh
  • 19. 1.Air Circuit Breakers 2.Air Blast Circuit Breakers 3. Vacuum Circuit Breakers 4.Oil Circuit Breakers 5.Sulfur hexafluoride circuit breakers 02/04/15Dr.Latif Shaikh
  • 20. 1.In this Circuit Breaker the arc is elongated using arc runners and arc splitters so as to increase the resistance of the arc. 3.This increases the voltage required to maintain the arc and if the available voltage cannot sustain the arc ,the arc gets extinguished. 2.At current zero ,the recovery voltage across the contacts becomes less than the arc voltage and the arc gets extinguished. 4. The energy in the system inductance at current zero is zero .Hence arc interruption is easier. 02/04/15Dr.Latif Shaikh
  • 22.  1 Main contacts  2 Arcing Contacts  3.Arc Rising in the direction of Arrow  4.Arc getting Split  5.Arc Splitter Plates  6.Current Carrying Terminals  7.Arc Runners 02/04/15Dr.Latif Shaikh Air Circuit Breakers
  • 23. 1.Used For low voltage levels and current levels 2.As voltage level increases, the size of breaker becomes large so not convenient for higher voltage and current levels. 3.Air is used as medium to extinguish the arc which have inferior extinguishing properties compared to SF6 or Vacuum circuit breakers 4.Operating control is manual as well as automatic. 5.It is used up to 6.6kV with a breaking capacity of 15MVA. 6.Suitable for repeated operation because medium of arc extinction is air. 02/04/15Dr.Latif Shaikh
  • 24. In this breaker, a high pressure air blast is used as an arc quenching medium. The contacts are opened and a flow of air blast is maintained by opening the blast valve. The air blast cools the arc and takes away the arcing products to atmosphere . This rapidly increases the dielectric strength of the medium between the contacts and the arc is extinguished and the flow of current is interrupted. 02/04/15Dr.Latif Shaikh
  • 26.  High speed of operation  Short arcing time  High speed reclosing  Less weigh as compared to oil circuit breakers  Very less maintenance  No possibility of explosion  Cost is more  For complete compress air installation is required  These breakers are more sensitive to RRRV.  For operation and maintenance ,highly skilled persons are required 02/04/15Dr.Latif Shaikh
  • 28. Air is admitted in the arc extinction chamber it pushes the moving contact. This air blast takes away the ionized gases along with it. Afterwards the arc gets extinguished. High pressure air has higher dielectric strength. The design is such that the air expands into the low pressure (atmospheric pressure zone).The air at high speed removes heat from the arc, thus arc is quenched. Diameter of arc is reduced. Uses 1.Arc Furnaces 2.Traction Syetems 02/04/15Dr.Latif Shaikh
  • 29. When two contactsof thiscircuit breaker areseparated in vacuum an arc isstruck and hot spotsareformed on thesurface of thecontacts.Thesehot spotsproducemetal vapor and plasma. Theamount of vapor in plasmadependson how rapidly the vapor isemitted from contact surfacewhich dependson thearc current. Thecurrent isof alternating nature, it passthrough zero several times, so therateof vapor emission also becomeszero, and thevapor already emitted getscondensed . During this processthedielectric strength buildsup rapidly and the restriking of arc isprevented. 02/04/15Dr.Latif Shaikh
  • 31. It consists of fixed contact, moving contact and arc shield mounted inside a vacuum chamber. The movable member is connected to the control mechanism by stainless steel bellows. This enables the permanent sealing of the vacuum chamber so as to eliminate the possibility of leakage,. A glass vessel or ceramic vessel is used as outer insulating body. The arc shield prevents the deterioration of the internal dielectric strength by preventing the deterioration of the internal dielectric strength. Applications – Outdoor application where maintenance required is minimum.In the high voltage system from 22 KV to 66kV power Circuits. 02/04/15Dr.Latif Shaikh
  • 32. When two contacts of circuit breaker are separated in vacuum arc is struck and hot spots are formed on the surface of the contacts. These hot spots produce metal vapour and plasma. At current zero the rate of vapour emission becomes zero. The vapour already emitted gets condensed . During this process the dielectric strength builds up and the restriking of arc is prevented. 02/04/15Dr.Latif Shaikh
  • 33.  Compact in size  Reliable and long life  Heavy fault can be interrupted effectively  No gas is generated after arc extinction operation  Operation is not noisy  Arc energy is low  No risk of fire  Vacuum has to be maintained at desired level always 02/04/15Dr.Latif Shaikh
  • 35. This breaker makes use of oil for quenching the arc. The circuit breaker which uses more oil or which is bulky is called bulk oil circuit breaker. The construction is simple and it consists of fixed and moving contacts enclosed in a strong weather – tight earthed tank containing oil up to a certain level and an air cushion above the oil level. Application These breakers are used up to 11 KV with an interrupting capacity of 250MVA. 02/04/15Dr.Latif Shaikh
  • 36. Under normal working conditions, thefixed and moving contactsare closed. On theoccurrenceof fault, themoving contactscomedown and an arc isstruck between thecontacts. Theoil between the contactsgetsdecomposed and hydrogen gasbubbleisformed around thecontacts. Thehydrogen gascoolsthearc and the turbulenceeffect causethelengthening of arc. Thedeionization of medium between contactstakesplaceand at somecritical length of gap between thecontacts,thearc isextinguished. Thehydrogen gasbubbleproducesavery high pressurein theoil. The tank isthereforemadestrong to withstand alargepressure. Theoil movesupwardswhen hydrogen bubbleisformed. Theair ispresent between theoil level and tank top and actsascushion and absorbs mechanical shock produced dueto upward oil movement. 02/04/15Dr.Latif Shaikh
  • 37.  oil has high dielectric strength  Oil absorbs arc energy while decomposing  Good cooling property of the gas formed due to decomposition  It acts as an insulator between the live parts and earth  Long arcing time  Do not permit high speed of interruption  Arc interruption control can be obtained only by increasing the length of arc  Chance of fire and explosion. 02/04/15Dr.Latif Shaikh
  • 38.  Operation  When the contacts are separated in oil arc is formed. The heat of arc decomposes oil and gases are formed. These gases expand due to heating of the arc. The gas flowing near the contact zone cause cooling and splitting of the arc and the arc gets extinguished. 02/04/15Dr.Latif Shaikh
  • 39. In this breaker, the supporting ,current interruption and top chamber are made of porcelain .Hence, clearance between live parts is small and requires less quantity of oil, hence the breaker is called Minimum Oil Circuit Breaker. The chambers are completely filled with oil. The oil from upper chamber does not come to lower. The fixed contact is enclosed in the quenching chamber. Moving contact makes sliding contact with the lower fixed contact. The operating rod is operated by operating mechanism, the three poles operate simultaneously.The voltage ratings are from 3.6kV to 420 KV. 02/04/15Dr.Latif Shaikh
  • 40.  Requires less quantity of oil  Requires smaller space  Maintenance is less  Cost per breaking capacity in MVA is less  Suitable for both manual and automatic operation  Possibility of fire and explosion.  Difficult to remove gases from the space between contacts.  Oil deteriorates rapidly due to carbonization  Smaller quantity of oil, so carbonization increases. 02/04/15Dr.Latif Shaikh
  • 41.  Electronegative –It has the ability of an atom to attract and hold electrons. Such gas have high dielectric stremngth.SF6 is electronegative .It forms negative ions ,Negative ions are heavy and immobile so they do not flow easily .Hence SF6 gas has high dielectric strength.  Rate of rise of dielectric strength is very high.  Can be liquefied and stored in steel tanks  Dielectric strength increase linearly with pressure.  Gas is inert. Therefore contacts will not get eroded.  Gas is non –inflammable , Colorless ,odorless, Non-toxic  Thermally stable up to 55 degrees 02/04/15Dr.Latif Shaikh
  • 43.  Under normal operating conditions the contacts are closed .  On occurance of fault contacts are opened. The movable contact moves away from the fixed contact.  The arc is struck between the fixed and moving contacts.  High pressure SF6 gas now flows over the arc and it absorbs the free electrons from the arc.  This builds up the dielectric strength between the gap very fast and the arc is extinguished 02/04/15Dr.Latif Shaikh
  • 44. Advantages  Silent operation, compact size  Vary short arcing time  No risk of fire  No reduction in dielectric strength due to operation  No moisture problem  No current chopping problem  Can interrupt larger currents  Suitable for explosive environment due to totally enclosed body Disadvantages  Costly  Requires conditioning of SF6 gas from time to time  SF6 gas is suffocating ,so its leakage can cause suffovcation of the persons in surrounding areas. 02/04/15Dr.Latif Shaikh
  • 46. Isolator(disconnecting switch) operates under no load condition. It does not have any current breaking capacity or current making capacity. Isolator is not even used for breaking load currents. Isolators are used in addition to circuit breakers ,and are provided on each side of every circuit breaker to provide isolation and enable maintenance. Sequence of operation While opening –Open circuit breaker first and then isolators While closing –Close isolators first and then close circuit breakers 02/04/15Dr.Latif Shaikh
  • 47. Different types of controls are required for successful operation of circuit breakers. 1.Relays – These are required to give a trip signal to circuit breaker in case of fault condition. Different types of relays are available like over current, over voltage ,under voltage, loss of excitation,reverse power etc. 2.Sensor equipments are required to check the condition of circuit breakers arc extinguishing medium . The controls are pressure sensors to sense the pressure of air in case of air blast circuit breakers . In case of Sulfur hexafluoride circuit breakers also the pressure sensors are required. In case of vacuum circuit breakers also sensors are required to check the vacuum level in the breaker. 02/04/15Dr.Latif Shaikh
  • 49.  The faults in power system may be temporary or permanent.  The temporary faults like touching of overhead conductors due to wind are cleared automatically after some time .  In case of temporary faults auto reclosing helps to maintain the system supply .  The breaker opens on a fault.  After some time delay ,the breaker is closed .  If the fault is temporary and it is removed ,then the breaker will close successfully  If the fault still persists then the breaker opens. 02/04/15Dr.Latif Shaikh
  • 51. Sectionalizers are used in the bus bars so that fault on any section of bus bar will not cause complete shut down. Advantages of sectionalizers 1.If fault occurs on any section of bus bars then that section is isolated from other sections without affecting the system. 2.Fault current is much lower than in case of un sectionalized system (as the fault is fed from only one section) 3.Repairing and maintenance on one section can be carried out by de energizing that section only eliminating the possibility of complete shut down. The breaker in the bus bars is acting as sectionalizing breaker in the shown figure. 02/04/15Dr.Latif Shaikh
  • 52. Fuse is a device used in circuit for protecting electrical equipments against overloads and /or short circuits. Fuse element or fuse wire is that part of the fuse device which melts when an excessive current flows in the circuit and thus isolates the faulty device from the supply circuit. Desirable qualities of fuse elements 1.Low melting point 2.Low ohmic losses 3.High conductivity 4.Free from deterioration due to oxidation 5.Low cost 02/04/15Dr.Latif Shaikh
  • 55. It consists of a heat resisting ceramic body having metal end caps. A fusible wire is welded to it. The space within the body, surrounding the element is completely packed with a powder, usually quartz, which acts as an arc extinguishing medium. Under fault condition, the current flowing through the element produces very large amount heat and the fuse element melts before the fault current reaches first peak value. The heat produced in the process vaporizes the melted fuse element. The chemical reaction between the silver vapor and filling power results in the formation of high resistance which helps quenching the arc. 02/04/15Dr.Latif Shaikh