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1. SF6 Circuit breaker in geothermal power substation.
Mexicali Baja California
SF6 CIRCUIT BREAKER
PRESENTED BY: POOJA GUPTA
ROLL NO : 1709120062
SEMESTER : 5TH
A PRESENTATION ON

2. CONTENTS
1. INTRODUCTION
2. HISTORY OF SF6 CIRCUIT BREAKERS
3. MOTIVATION AND FEASIBILITY OF THIS TOPIC
4. WHAT IS A CIRCUIT BREAKER?
5. TYPES OF CIRCUIT BREAKER
6. WHY SF6 GAS IS USED?
7. PHYSICAL PROPERTIES
8. CHEMICAL PROPERTIES
9. WHAT IS SF6 CIRCUIT BREAKER?
10. CONSTRUCTION
11. WORKING PRINCIPLE
12. ADVANTAGES
13. DISADVANTAGES
14. APPLICATIONS
15. CONCLUSION
16. REFERENCES

3. • The first industrial application of SF6 for current interruption dates to 1953. High-voltage 15 kV to
161 kV load switches were developed with a breaking capacity of 600 A.
• The first high-voltage SF6 circuit breaker built in 1956 by Westinghouse, could interrupt 5 kA under
115 kV, but it had six interrupting chambers in series per pole.
• In 1957, the puffer-type technique was introduced for SF6 circuit breaker.
• The first high-voltage SF6 circuit breaker with a high short-circuit current capability was produced
by Westinghouse in 1959.
• The excellent properties of SF6 led to the fast extension of this technique in the 1970s and to its use
for the development of circuit breakers with high interrupting capability, up to 800 kV.
HISTORY OF SF6 CIRCUIT BREAKERS

4. MOTIVATION AND FEASIBILITY OF THE TOPIC
HAVELLS INDIA LIMITED one of the largest electrical equipment
companies in India has targeted Rs 1,000 crore revenue from
building circuit protection devices over three years with the
launch of its new series of technologically advanced miniature
circuit breakers (MCB) and residual current circuit breakers
(RCCB) with six years warranty for the first time
The report Global Circuit Breakers Market is expected to
cross USD 21 Billion by 2024, as reported in the latest study
by Global Market Insights, Inc. Affirmative regulatory
mandates toward the development of cross border electric
infrastructure to sustain the rising demand for the
refurbishment of ageing transmission network will foster
the circuit breaker market.

5. WHAT IS A CIRCUIT BREAKER?
It is an equipment which can open or close a circuit under normal condition as well as under fault conditions.
A relay is always used with circuit breaker whose purpose is to sense the fault current and to energise the trip coil and relay coil.
CIRCUIT DIAGRAM OF
CIRCUIT BREAKER
TYPES OF CIRCUIT BREAKER
1. OIL CIRCUIT BREAKER (≤ 11 kV)
2. AIR BLAST CIRCUIT BREAKER (≥ 110 KV)
3. SF6 CIRCUIT BREAKER ( 50 KV TO 230 KV)
4. VACCUM CIRCUIT BREAKER ( 22KV TO 66 KV)

6. WHY SF6 GAS IS USED?
SF6 gas is used because of its excellent physical and chemical properties.
PHYSICAL PROPERTIES:
• SF6 is one of the heaviest known gases.
• The variation of pressure with temperature is linear and
linearly small in the range of service temperatures (-25 to
50◦C).
• The specific heat of SF6 is 3.7 times that of air.
VAPOUR PRESSURE CURVE AND
EQUIVALENT GAS DENSITY IN SF6.

7. CHEMICAL PROPERTIES:
• SF6 fully satisfied the valence requirements of the sulfur molecule. Its molecular structure is
octahedral with a fluorine molecule at each apex. The six bonds are covalent which accounts
for the exceptional stability of this compound.
• SF6 can be heated without decomposition to 500°C in the absence of catalytic metals. SF6
is non-flammable and hydrogen, chlorine, and oxygen have no action on it. SF6 is insoluble in
water and is not attacked by acids.

8. WHAT IS A SF6 CIRCUIT BREAKER?
A circuit breaker in which SF6 under pressure gas is used to extinguish the arc is called SF6 circuit breaker.
CONSTRUCTION
• SF6 circuit breakers mainly consist of two parts:
(a) Interrupter Unit (b) Gas System.
INTERRUPTER UNIT
GAS SYSTEM

9. CONSTRUCTION
1.INTERRUPTER UNIT: This unit consists of
moving and fixed contacts comprising a set of
current carrying parts and an arching probe. It is
connected to the SF6 gas reservoir. This unit
consists of slide vents in the moving contacts
which permits the high pressure gas into the main
tank.
2.GAS SYSTEM: The closed circuit gas system is employed in SF6 circuit breakers. The SF6 gas is costly, so it
is reclaimed after each operation. This unit consists low and high-pressure chambers with a low-pressure alarm
along with warning switches. When the pressure of the gas is very low due to which the dielectric strength of
gases decrease and an arc quenching ability of the breakers is endangered, then this system gives the warning
alarm.

10. WORKING PRINCIPLE :
• In the closed position of the breaker, the
contacts remain surrounded by sulphur
hexafluoride gas (SF6) gas at a pressure of
about 2.8 kg/cm2.
• When the breaker operates, the moving contact is pulled apart
and an arc is struck between the contacts. The movement of
the moving contact is synchronized with the opening of a
valve. The valve permits sulphur hexafluoride gas (SF6) gas at
14 kg/cm2 pressure from the reservoir to the arc interruption
chamber.
The high-pressure flow of sulphurhexafluoride gas (SF6) rapidly absorbs the free electrons in the arc path. It forms immobile negative ions which are
ineffective as charge carriers.
The result is that the medium between the contacts quickly builds up high dielectric strength and causes the extinction of the arc.
After the breaker operation (i.e. after arc extinction in circuit breaker), the valve is closed by the action of set of springs.

11. TYPES OF SF6 CIRCUIT BREAKER:
• Single Interrupter SF6 CB applied up to 200 kV
• Two Interrupter SF6 CB applied up to 420 kV
• Three Interrupter SF6 applied up to 800 kV
SINGLE
INTERRUPTER
THREE
INTERRUPTER

12. ADVANTAGES
• The current chopping tendency is minimized by using the gas SF6 at low pressure and velocity.
• The closed circuit gas cycle and low velocity operation eliminates the moisture problem and gives noiseless
operation of the breaker.
• Because of the outstanding arc quenching properties of SF6 , the arcing time is small , and, therefore
contact erosion is less.
• No carbon particle is formed during arcing and, therefore, there is no reduction in the dielectric strength of
the gas.
• The circuit breaker performance is not affected due to atmospheric conditions.
• Electrical clearances are drastically reduced due to high dielectric strength of SF6.

13. • Imperfect joints leads to the leakage of the SF6 gas .Continuous monitoring devices are required.
• Arched SF6 gas is poisonous and should not be inhaled.
• SF6 gas being heavier than air settles in the surroundings and may lead to suffocation of the operating personal. However, it is not
poisonous.
• It may contribute to the man made greenhouse effect, if it is released in the atmosphere.

14. APPLICATIONS
• A typical SF6 circuit breaker consists of interrupter units each capable of dealing with currents upto 60kA and voltages
in the range of 50-80kV.
• A number of units are connected in series according to the system voltage.
• SF6 circuit breaker have been developed for voltages 115kV to 230kV.
• Power ratings 10 MVA to 20 MVA and interrupting time less than three cycles.

15. CONCLUSION
SF6 circuit breakers are mostly employed for high voltage applications.
There are countless advantages of using SF6 gas as mentioned earlier.
As we have seen, these circuit breakers are in high demand in market,
And revenue generated by the companies is also high.

16. REFERENCES
• https://studyelectrical.com/2014/07/sulphur-hexaflouride-sf6-circuit-breaker-construction-working-
advantages.html
• https://www.electricalengineeringinfo.com/2016/03/sf6-circuit-breakers-working-and-construction-sf6-
circuit-breakers.html
• https://circuitglobe.com/sf6-sulphur-hexaflouride-circuit-breaker.html
• https://studyelectrical.com/2014/07/sulphur-hexaflouride-sf6-circuit-breaker-construction-working-
advantages.html
• https://www.slideshare.net/khalid9z/sf6-circuit-breaker-by-khalid-nit-warangal
• https://geometryofmolecules.com/sf6-lewis-structure-shape-and-polarity/
• https://www.globenewswire.com/news-release/2018/10/29/1638060/0/en/Circuit-Breaker-Market-
revenue-worth-over-21-billion-by-2024-Global-Market-Insights-Inc.html
• https://en.wikipedia.org/wiki/Sulfur_hexafluoride_circuit_breaker
• https://www.marketsandmarkets.com/Market-Reports/circuit-breaker-and-fuse-market-1237.html
• https://economictimes.indiatimes.com/industry/cons-products/electronics/havells-targets-rs-1000-
crore-revenue-from-switchgears-in-three-years/articleshow/69960755.cms?from=mdr
• https://www.elprocus.com/types-of-circuit-breakers-and-its-application/
• https://www.prnewswire.com/in/news-releases/circuit-breaker-market-worth-868-billion-usd-by-2022-
668438903.html

17. THANK YOU !