Digital testing of high voltage circuit breaker

1. DIGITAL TESTING OF HIGH
VOLTAGE CIRCUIT BREAKER
MADE BY:-NEERAJ PRASAD
ROLL NO:-18
3ND YEAR EE
SURENDRA INSTITUTE OF ENGINEERING &
MANAGEMENT

2. CONTENT
• Origin
• Introduction
• Types of HV circuit breaker
• Oil circuit breakers
• Air blast circuit breakers
• Sulphur hexafluroide circuit
breakers(SF6)
• Vacuum circuit breakers

3. • Need for testing
• Digital testing
• Testing of circuit breaker
• Aim of digital testing
• Advantages &Disadvantages
• Conclusions

4. Origin
• An early form of circuit
breaker was described
by Thomas Edison in an
1879 patent application,
although his commercial
power distribution system
used fuses.
• Its purpose was to protect
lighting circuit wiring from
accidental short circuits
and overloads.

5. Introduction
What is a circuit breaker?
• A circuit breaker is a device which can
make or break a circuit, either manually or
automatically under all conditions .Like
no-load, full-load and short-
circuit conditions.

6. High-voltage breakers are broadly classified
by the medium used to extinguish the arc.
• Oil circuit breakers
• Air blast circuit breakers
• Sulphur hexafluroide circuit
breakers(SF6)
• Vacuum circuit breakers

7. Oil circuit breakers
It is designed for 11kv-765kv.
These are of two types
• BOCB (Bulk oil Circuit Breaker)
• MOCB (Minimum oil Circuit Breaker)
The contacts are opened under the oil and arc is struck
between them.
The heat of arc evaporates the surrounding oil and dissociates it
into a substantial volume of gases hydrogen at high pressure.
The hydrogen gas occupies a volume about one thousand times
that of oil decomposed.
The oil is ,therefore pushed away from the arc and expanding
hydrogen gas bubble surrounds the arc region and adjacent
portions of the contact as see in fig.

9. • Advantages:
1.Oil has good dielectric strength.
2.Low cost.
3.It has wide range of breaking capability.
Disadvantages:
1.Slower operation , takes about 20 cycles for arc
quenching.
2.It is highly inflammable , so high risk of fire.
3.High maintenance cost.

10. VACCUM CIRCUIT BREAKER
It is designed for medium voltage range (3.3-33kv).
This consists of vacuum of pressure (1*10-6) inside
arc extinction chamber.
The arc burns in metal vapour when the contacts
are disconnected.
At high voltage , it’s rate of dielectric strength
recovery is very high.
Due to vacuum arc extinction is very fast.
The contacts loose metals gradually
due to formation of metal vapours.

12. Advantages:
1.Free from arc and fire hazards.
2.Low cost for maintenance & simpler mechanism.
3.Low arcing time & high contact life.
4.Silent and less vibrational operation.
Disadvantages:
1.High initial cost due to creation of vacuum.
2.Surface of contacts are depleted due to metal vapours.
3.High cost & size required for high voltage breakers.

13. AIR BLAST CIRCUIT BREAKERS
This operates using high velocity blast of air
which quenches the arc.
It consists of blast valve , blast tube & contacts.
Blast valve contains air at high pressure.
Blast tube carries the air at high pressure &
opens the moving contact attached to spring.
There is no carbonization of surface as in VCB.
Air should be kept clean & dry to operate it
properly.

15. Advantages:
1.High speed operation as compared to OCB.
2.Ability to withstand frequent switching.
3.Facility for high speed reclosure.
4.Less maintenance as compared to OCB.
Disadvantages:
1.Little moisture content prolongs arcing time.
2.Pressure should be checked frequently for
frequent operation.
3.Risk of fire hazards due to over voltages.
4.It can’t be used for high voltage operation due
to prolonged arc quenching.

16. SF6 CIRCUIT BREAKERS
 It contains an arc interruption chamber containing SF6 gas.
 In closed position the contacts remain surrounded by SF6 gas
at a pressure of 2.8 kg/cm2 .
 During opening high pressure SF6 gas at 14 kg/cm2 from its
reservoir flows towards the chamber by valve mechanism.
 SF6 rapidly absorbs the free electrons in the arc path to form
immobile negative ions to build up high dielectric strength.
 It also cools the arc and extinguishes it.
 After operation the valve is closed by the action of a set of
springs.
 Absorbent materials are used to absorb the byproducts and
moisture.

18. Advantages:
1.Very short arcing period due to superior arc quenching
property of SF6 .
2.Can interrupt much larger currents as compared to other
breakers.
3.No risk of fire.
4.Low maintenance cost.
5.No over voltage problem.
6.There are no carbon deposits.
Disadvantages:
1.SF6 breakers are costly dueto high cost of SF6 gas.
2.SF6 gas has to be reconditioned after every operation of the
breaker, additional equipment is required for this purpose.

19. Need for testing HV circuit breaker:-
• When an overload or a short circuit occurs
in the home or industry, the usual result is
a blown fuse or a tripped circuit breaker.
• Circuit breakers are mechanical devices,
which are subject to deterioration due to
wear, corrosion and environmental
contamination, any of which could cause
the device to remain closed during a
fault condition.

20. Testing of circuit breakers:-
• Routine tests
• Type tests

21. Digital testing
A project started with the following
parties :
• KEMA high power laboratories The
Netherlands.
• Delft University of technology, The
Netherlands.
• Siemens AG, Germany
• RWE Energy ,Germany

22. Aim of digital testing:-
• Developing digital testing of HV circuit
breakers. I.e. , a software product for testing
a model of such a device , once its
characteristic fingerprints are obtained from
refined measurements during standard tests.
• Digital offers a wide range of new possibilities
for users , manufactures, standardizing
bodies and test laboratories for fine tuning
circuit breaker abilities in relation with
standard and real power systems.

23. Advantages:-
• Evaluation of the relevance of future standards for
different circuit breaker technologies and extinguishing
media.
• Reduction of full scale testing in high-power laboratories.
• Identification of network topologies that can pose special
difficulties to a circuit breaker.
• Acceleration at development of new circuit breaker
design.
• Monitoring the aging process of circuit breaker in
service.

24. Disadvantages:-
• Testing in costlier
• Testing is time consuming
• A tough procedure

25. Conclusion:-
• Digital testing gives precise information
about the breaker, as obtained
from laboratory tests.
• This is useful for the development of future
standards.
• Powerful possibilities with digital testing
are created when arc model and data
analysis is coupled with a circuit analysis
package.