PRESENTATION TOPIC:
TYPES OF CIRCUIT BREAKERS
SUBJECT: ADVANCED POWER SYSTEM PROTECTION
PRESENTED BY:ENGR.MUHAMMAD AJAZ ANJUM
MS ELECTRICAL ENGINEERING (FALL-2023)
TEACHER: ENGR. MUHAMMAD KAMRAN sb
CIRCUIT BREAKER
 A circuit breaker is an electrical safety device designed to protect an
electrical circuit from damage caused by overcurrent. Its basic function
is to interrupt current flow to protect equipment and to prevent the risk
of fire. Unlike a fuse, which operates once and then must be replaced,
a circuit breaker can be reset (either manually or automatically) to
resume normal operation.
ARC FORMATION ISSUE
 During opening of current carrying contacts in a circuit breaker the
medium in between opening contacts become highly ionized through
which the interrupting current gets low resistive path and continues to
flow through this path even the contacts are physically separated.
During the flowing of current from one contact to other the path
becomes so heated that it glows. This is called arc.
 Thermal ionization of Gas & Ionization due to Electronic collusion
TYPES OF CIRUIT BREAKERS
TYPES COVERED IN PRESENTATION
 OIL CIRCUIT BREAKERS
 AIR CIRCUIT BREAKERS
 VACCUM CIRCUIT BREAKERS
 SF6 CIRCUIT BREAKERS
 HVDC BREAKERS
AIR BLAST CIRCUIT BREAKER
 The Air Blast Circuit breaker is a type of circuit breaker where at high
pressure the air blast is used for arc extinction in the electrical circuit.
The main principle behind it is that it has a fixed contact and a moving
contact, where high pressure is applied for arc extinction in a circuit
breaker. This is done to avoid the overflow of the electric current.
WORKING
 When the circuit breaker is under normal conditions, the breaker
contacts present in the arc extinction chamber are in touch with
each other.
 Under faulty conditions, the valves open with the help of an iron
rod.
 When the valves open, the air with high pressure enters the arc
extinction chamber via a hollow chamber setup.
 This increases the pressure on the moving contacts and eventually
gets separated from the fixed contact.
 During separation, an arc is created between the two contacts, due
to the ionization of air present between the two contacts.
 This ionized air is taken out due to high pressure via the outlet
valves and the arc formed is extinguished.
 After the circuit is broken successfully and the fault has been
cleared, the values close up and the pressure on the moving
contacts eventually drops.
AIR BREAK CIRCUIT BREAKER
 Air break circuit breaker uses atmospheric pressure in air as an air quenching
medium. This type of circuit breaker employs a high resistance interruption principle.
 When the breaker is in close condition, the current flows in the main contact. When
the contacts are open, the main contact is separated first and the arcing contact
remains closed.
 Therefore, the current in the main contact moves to the arcing contact. Now the
arcing contacts are separated and an arc is formed between them. Here, the high
resistance is used for arc interruption.
 The lengthening, splitting, and cooling the arc increases the resistance. The two
chambers called arc runner (Arcing horns) and arc chutes increases the length of the
arc. The arc moves along the arc runner and forced to move upwards into the arc
chute. The arc is split in this way by arc splitters and thus it extinguishes.
ADVANTAGES & APPLICATIONS
ADVANTAGES
APPLICATIONS
 They are cost-effective and readily
available in the market.
 These equipment are chemically
stable.
 The chance of fire hazard is
eliminated.
 Consistent arcing at short time
intervals causes less burning of
contact valves.
 Can work with high voltages and at
a higher speed.
 They are sustainable and have a
low cost of maintenance.
 They are used to control transient
over voltages at major power
stations and industrial plants.
 They protect the machines
operating at high voltages like
power transformers, capacitors,
AC generators and DC generators.
 They can also be used as fire
extinguishers.
 Due to the high resistance power,
it can increase the resistance of the
arc chamber.
VACUUM CIRCUIT BREAKER
 A breaker which used vacuum as an arc extinction medium is called a vacuum circuit
breaker. In this circuit breaker, the fixed and moving contact is enclosed in a
permanently sealed vacuum interrupter. The arc is extinct as the contacts are
separated in high vacuum. It is mainly used for medium voltage ranging from 11 KV
to 33 KV.
 At current zero this vacuum arc is extinguished and the conducting metal vapor is recondensed on the contact surface. At this point, the contacts are already separated
hence there is no question of re-vaporization of the contact surface, for the next cycle
of current. That means, the arc cannot be reestablished again. In this way vacuum
circuit breaker prevents the reestablishment of arc by producing high dielectric
strength in the contact gap after current zero.
PROS
 Vacuum circuit breaker has a high insulating medium for arc extinction as
compared to the other circuit breaker. The pressure inside the vacuum
interrupter is approximately 10-4 torrent and at this pressure, very few
molecules are present in the interrupter. The vacuum circuit breaker has
mainly two phenomenal properties.
 High insulating strength: In comparison to various other insulating media
used in circuit breaker vacuum is a superior dielectric medium. It is better
than all other media except air and SF6, which are employed at high
pressure.
 When an arc is opened by moving apart the contacts in a vacuum, an
interruption occurs at the first current zero. With the arc interruption,
their dielectric strength increases up to a rate of thousands time as
compared to other breakers.
 The above two properties make the breakers more efficient, less bulky
and cheaper in cost. Their service life is also much greater than any other
circuit breaker, and almost no maintenance are required.
ADVANTAGES & APPLICATIONS
ADVANTAGES
 Vacuum circuit breaker does not
require any additional filling of oil
or gas. They do not need periodic
refilling.
 Rapid recovery of high dielectric
strength on current interruptions
that only a half cycle or less arcing
occurs after proper contact
separation.
 Breaker unit is compact and selfcontained. It can be installed in
any required orientation.
 Because of the above reasons
together with the economic
advantage offered, vacuum circuit
breaker has high acceptance.
APPLICATIONS
 Because of the short gap and excellent
recovery of vacuum circuit breaker,
they are very useful as very high speed
making switches in many industrial
applications.
 When the voltage is high and current
to be interrupted is low these breakers
have definite superiority over the other
breakers.
 For low fault interrupting capacities
the cost is low in comparison to other
interrupting devices.
 Because of the least requirements of
maintenance, these breakers are very
suitable for the system which requires
voltage from 11 to 33 kV
SF6 CIRCUIT BREAKER
 The arc generated in the gas circuit breaker is extinguished in a chamber filled with
pressurized sulfur hexafluoride gas (SF6). It is a non-flammable, inorganic gas that is
an excellent electrical insulator.
 The arc generated in the gas circuit breaker is extinguished in a chamber filled with
pressurized sulfur hexafluoride gas (SF6). It is a non-flammable, inorganic gas that is
an excellent electrical insulator.
ADVANTAGES & APPLICATIONS
 The property of SF6 gas is arc quenching that is 100 times effective as compared to
air.
 Very short arcing time.
 Large current can be interrupted because of high dielectric strength.
 This CB includes a closed circuit gas system through no leakage. So, it can be
connected in any type of severe environment.
 SF6 gas is not flammable and nontoxic
 Requires low maintenance
 The SF6 switchgear is suitable for voltages up to 66 kV for armored switchgear and
800 kV for gas insulated switchgear (GIS).
 The pressure of the SF6 gas can be easily controlled. The insulating medium does
not present a fire/explosion hazard.
 These are used almost exclusively in outdoor applications and are increasingly
favored over oil breakers due to their lower maintenance costs.
 A distinct advantage that gas breakers have over vacuum breakers is that the gas
bottle loses pressure, and the residual SF6 gas may be enough to allow the breaker
to open safely under normal load.
OIL CIRCUIT BREAKER
 An oil circuit breaker is a traditional type of circuit breaker. It has a separate contact.
This contact’s primary function is to separate the insulating oil. When a fault or
problem occurs, this includes good comparable properties to air, which opens in the
lower part of the breaker contact oil.
 When the arc strikes between the two breaking contacts, the heat from the arc
dissolves the oil around it, and the high pressure separates some gaseous hydrogen.
The unique feature of this circuit breaker is its low cost, reliable operation, and ease
of use.
ADVANTAGES & APPLICATIONS
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Advantages
Oil circuit breakers are used in high-voltage applications such as power grids,
substations, powerlines, and transmission and distribution systems with voltage
ratings of up to 220 kV
It consumes less oil.
Oil has a high dielectric strength.
When the oil in the breaker decomposes, it absorbs arc energy.
Fire risk can be reduced by using less space.
Maintenance has also been reduced.
Disadvantages
It uses less oil, so the amount of carbonization is increased.
It is difficult to remove the gases from the contact space.
Because of the high amount of carbonization, the dielectric strength of the oil will
rapidly decline.
The racing time is long.
Do not allow high-speed interruptions.
DC CIRCUIT BREAKER
 DC circuit breakers refer to circuit breakers used in DC power distribution systems from
overcurrent and potential hazards
 The signal of AC current is constantly changing its value for every second. The circuit
breaker arc will be extinguished at 0 volts, and the circuit will be protected from big
current, But the signal of DC current is not alternating, it works in a constant state, and the
voltage value will only change when the circuit is tripped or the circuit is reduced as a
certain value, Otherwise, the DC circuit will provide a constant voltage value for every
second of a minute. Therefore, since there is no 0 volt point in the DC state, it does not
suggest that use a AC circuit breaker for the DC state.
 Thermal protection trips the DC circuit breaker when electric current above the rated
value is present. This protection mechanism is based on a bimetallic contact that heats,
expands and trips the circuit breaker. The thermal protection works faster as the current
grows larger because more heat is generated to expand and open the electric contact.
Thermal protection in a DC circuit breaker protects against overload current, which is
only slightly larger than normal operating current.
 Magnetic protection trips the DC circuit breaker when high fault currents are present, and
the response is always instantaneous. DC circuit breakers have a rated breaking capacity
that represents the maximum fault current that can be interrupted, just like AC circuit
breakers. An important consideration with DC circuit breakers is that the current being
interrupted is constant, so the circuit breaker must open the electric contact further in
order to interrupt the fault current. Magnetic protection in a DC circuit breaker protects
against short circuits and faults, which are drastically larger than an overload.
DC CIRCUIT BREAKERS
 In DC substations or DC microgrids, direct current circuit breakers
(DCCBs) are used. DCCBs, as the name suggests, are used for the
protection of electrical devices that operate on direct current. The
main difference between direct current and alternating current is that
in DC the voltage output is constant, while in AC it cycles several
times per second. For a 60 Hz frequency system, an AC signal
changes its polarity 120 times and 120 times the signal passes
through the zero-crossing. As there is no zero-crossing in the DC
signal, arc quenching in the DCCB is a hurdle. Because of the
absence of the arc quenching methods in DCCB, DC grids did not
develop as the AC grids developed
TYPES OF DC CIRCUIT BREAKERS
The main three types of DC breakers are
 Mechanical DC breakers,
 Solid-state DC breakers
 hybrid DC breakers.
MECHANICAL DC CIRCUIT BREAKERS
 A mechanical DC breaker is the simplest and most conventional
DCCB. It consists of three parallel paths: nominal current path,
commutation path, and energy absorption path, as shown in below
Figure . During the normal operation of the system, the CB is closed
in the nominal current path, giving a low resistive path to the current
to pass through. On the occurrence of a fault, contacts in the
nominal current path are opened that produce an arc. The arc
produced is quenched either by introducing an artificial resonance
circuit for zero-crossing interruption of the fault current or by
lengthening the arc and cooling.
SOLID STATE DC CIRCUIT BREAKERS
 With the advancement in power electronics, various semiconductor
power switches have been introduced that could be used as current
commutation devices in solid-state DC CBs. These power
electronics devices include insulated gate bipolar transistors
(IGBTs), IGCTs, thyristors, and gate turn-offs (GTOs) that are
suggested for the DCCB. However, IGBTs and IGCTs are
preferred for solid-state DC CBs
 Novel concept of SSCB uses normally ON semiconductor static
switches to interrupt the fault current. During a fault, the rising
terminal voltage is detected and the switches are turned OFF,
diverting the fault current to the energy absorption path.
HYBRID DC CIRCUIT BREAKERS
 The generic structure of a hybrid DCCB is shown in Fig., consisting of three
parallel branches: a nominal current path consisting of a combination of
commutating element and an isolating switch.
A secondary branch contains
semiconductor switches.
 On a fault in the circuit, semiconductor switches in the secondary branch are on
and provide a bypass to the fault current. The third branch is the energy
absorption branch consisting of a MOV
 Ultra-fast developed DC breaker, presented in right Fig., consists of two branches:
the main breaker consisting of various IGBT switches with parallel surge arrestors
and a bypass branch formed by a load commutation switch (LCS) in series with an
ultra-fast mechanical disconnector (UFD). Under normal conditions, the main
breaker remains off and the current passes through the bypass branch that reduces
the conduction losses since no current passes through the IGBTs.
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