The document discusses the key components found in electrical substations, focusing on circuit breakers. It describes the functions and types of circuit breakers, how they operate, and the tests used to evaluate their performance. Specifically, it outlines the critical roles circuit breakers play in switching during normal and abnormal operating conditions, as well as interrupting faults. It also examines the mechanisms, dielectric mediums like SF6 gas, and rated characteristics that determine a circuit breaker's capabilities.

1. Components in a
substation -
CIRCUIT BREAKER

2. Components in a sub - stationComponents in a sub - station
Circuit Breaker
Isolators
Lightning Arrestors
Power Transformer
Current Transformer
Potential Transformer
Auto Transformer
Control & Relay panel
Batteries & Charger
Bus bar
Insulators
Connectors
Control cables

3. CIRCUIT BREAKERSCIRCUIT BREAKERS
 Switching and current interrupting device
 Serves two basic purposes
 Switching normal operating conditions
- for operation & maintenance
 Switching abnormal operating conditions
 Clearing short circuits & Interrupting fault
currents
Contd…

4. CIRCUIT BREAKERS(contd.,CIRCUIT BREAKERS(contd.,
 Should be capable of :
 Carrying normal load current
 Make and Break load current
 Make and Break abnormal fault current
 Performing few or many operations in a year
 Operating in elevated & reduced temperature
areas

5. HISTORY OF CIRCUIT BREAKERHISTORY OF CIRCUIT BREAKER
 Knife & Mercury Switches
 Oil Circuit Breakers (1885)
 Minimum Oil Circuit Breakers
 Air Blast Circuit Breaker (1930)
 SF6 Breakers (1950)
 Double pressure type SF6 Breakers
 Puffer type SF6 Breakers
 Vacuum Circuit Breakers

6. CLASSIFICATION OF CIRCUIT BREAKERSCLASSIFICATION OF CIRCUIT BREAKERS
Based on Construction
Indoor application
Outdoor application
Based on method of Arc Extinction
High Resistance Interruption
Zero Point Interruption

7. Dielectric Medium used for Arc ExtinctionDielectric Medium used for Arc Extinction
Air Break CBs - (LT Application)
Air at atmospheric Pressure
Air Blast CBs- High Pressure Air
Oil CBs - Dielectric Oil
SF6 CBs -SF6 Gas at 4-7Bar Pressure
Vacuum CBs - Vacuum

8. Functions of operating mechanismFunctions of operating mechanism
 To provide means whereby the CB can be
CLOSED rapidly without hesitation
 To HOLD the CB in closed position by latches till a
trip signal is received
 To allow the CB to OPEN without delay on
receiving the trip signal
 To have Sufficient energy to operate the moving
parts rapidly and smoothly.
Contd…

9. Functions of operating mechanism (contd…)Functions of operating mechanism (contd…)
Mechanism should be capable of operating
by conventional low power control circuits
Mechanism should have a positive action
(ON or OFF - not in between)
Reliable
Capable of performing auto reclose cycle

10. TYPES OF MECHANISMTYPES OF MECHANISM
“Dependable”-Continuity of power supply
(Manual & Power)
 “Stored Energy type”
- Energy is stored in Charged Spring/
Compressed Air / Hydraulic Oil
- Independent of continuity of power
supply

11. Types of stored Energy Mechanism used inTypes of stored Energy Mechanism used in
Circuit BreakersCircuit Breakers
 Spring Closed, Spring Opened
 Solenoid Closed, Spring Opened
 Hydraulic
 Pneumatic
 Pneumatic Closed, Spring Opened
 Spring Closed, Pneumatically Opened

12. ARCARC EXTINCTION IN C.BEXTINCTION IN C.B
 In AC (50 Hz) current will be Zero at the end of
each half cycle(i.e 100 times / Sec.)
 For efficient Arc Extinction, Breaker must
establish good insulation between contacts very
quickly. This is achieved by removing any ionised
material from between contacts and replacing it
with insulating material
(Contd..)

13. ARC EXTINCTION IN C.B (Contd..)ARC EXTINCTION IN C.B (Contd..)
 Arc Extinction in Oil
 Arc Extinction in Air Blast
 Arc Extinction in Vacuum- No free Electrons
 Arc Extinction in SF6
SF6-atoms-molecules–attract & hold free electrons
 Arc Extinction with multiple breaks
 Resistor interruption
To reduce the over voltages & transients because of
rapid changes in current level

14. Advantages of SF6 Circuit BreakerAdvantages of SF6 Circuit Breaker
 More compact design than other CBs of similar
capacity.
 Operation is relatively quiet.
 High pressure Air compressors and large
reservoirs not required.
 Fewer moving parts hence lesser maintenance.
 Gas is stable - absence of contact erosion.

15. Disadvantages of SF6 Circuit BreakerDisadvantages of SF6 Circuit Breaker
 SF6 gas is expensive
 Some toxic products are produced under
operating conditions
 Gas filling and emptying requires skill and costly
gas filling and evacuating equipments
 Leakage may cause serious problem & very
difficult to find out

16. Properties of SF6 Gas:Properties of SF6 Gas:
Physical:
 Colourless, odourless, nontoxic
 Pure gas is not harmful to health, Non-inflammable
 Gas at normal pressure & Temperature
 Gas density - 5 times that of air at 20 deg.C and
atmospheric pressure

17. Properties of SF6 GasProperties of SF6 Gas
 Chemical:
 Stable upto 500 Deg. Centigrade.
 Inert – Chemical inert – Metallic parts, contacts have
longer life.
 Electronegative.
 Does not react with structural materials upto 500 Deg.
Centigrade.
 Products of decomposition SF2 & SF4 recombine on
cooling.
 Metallic Fluorides are good insulators.

18. Dielectric properties of SF6Dielectric properties of SF6
 DE strength of SF6 at atmospheric pressure is 2.35
times that of air and 30 % less than that of oil.
 At high pressure DE strength increases.
 At 3 kg/cm2 DE strength is more than that of oil.
 This property permits smaller clearances and
smaller equipment.

19. RATED CHARACTERISTICS OF CIRCUITRATED CHARACTERISTICS OF CIRCUIT
BREAKERSBREAKERS
Rating denotes C.Bs capabilities under specified
conditions. Ratings are based on IEC
recommendations.
Rated Voltage:
Corresponds to the highest system voltage for
which the CB is intended.
Rated insulation level:
Power frequency withstand voltage Impulse
withstand voltage.

20. RATED CHARACTERISTICS OF CIRCUITRATED CHARACTERISTICS OF CIRCUIT
BREAKERSBREAKERS
Rated Frequency:
Standard frequency of the power system
Rated Current: (rms value of the current)
CB can carry continuously with temperature rise
of the various parts within specified limits
Rated S.C. Current:
Highest value of short circuit current which the
CB is capable of breaking.(Expressed in KA).

21. RATED CHARACTERISTICS OF CIRCUITRATED CHARACTERISTICS OF CIRCUIT
BREAKERSBREAKERS
Rated SC making current:
At times the CB close on to a existing fault.
CB must be capable of closing without hesitation.
CB must be able to withstand high Mechanical forces.
Rated SC making current should be at least 2.5 times
SC current.

22. RATED CHARACTERISTICS OF CIRCUITRATED CHARACTERISTICS OF CIRCUIT
BREAKERSBREAKERS
Rated duration of SC:
1 Sec. Or 3 Sec.
Rated operating duty:
i. o- t – co – T – co
t = 0.3 Sec. T = 3 Min.
ii. co – t’ – co t’ = 15 Sec.

23. TESTS ON CIRCUIT BREAKERSTESTS ON CIRCUIT BREAKERS
Type test – Capability of the Breaker
Routine test – Proper functioning of the Breaker

24. TYPE TESTTYPE TEST
 Mechanical Endurance Test
 Temp Rise Test
 Measurement of DC Resistance
 Milli volt Drop Test
 No load operation test(includes closing opening
operating sequence)
 Dielectric tests
 Basic Short circuit test

25. Routine TestRoutine Test
 Mechanical test
 MV drop test
 Measurement of DC Resistance
 Power Frequency withstand test
 Voltage test on Aux Circuits
 IR Value of main & Aux. Circuits

26. 1
GL 312GL 312
3 9 9 0
23002905
123/145 kV • 3150 A • 40 kA

27. Q
GL 312- Three-Phase AssemblyGL 312- Three-Phase Assembly

28. GL314 SF6 Circuit breakerGL314 SF6 Circuit breaker
GL314 on site

29. Interrupting chamber - GL314Interrupting chamber - GL314
‘CLOSED’
position
Thermal effect +
compression stage
Thermal effect ‘OPEN’ position
Vt
Vc
Vt : thermal volume
Vc : compression volume

30. InterruptingInterrupting
..7.Electrical Pres_Supportingvalcbtemp.mp..7.Electrical Pres_Supportingvalcbtemp.mp
chamber - GL314chamber - GL314

31. with smallwith small
currentcurrent
with smallwith small
currentcurrent
with short-circuitwith short-circuit
currentcurrent
with short-circuitwith short-circuit
currentcurrent
GL 312GL 312
Closed positionClosed position
InterruptionInterruption
Open positionOpen position
Closed positionClosed position
InterruptionInterruption
Open positionOpen position
Interruption

32. Circuit Breaker Testing.mp4

33. Testing Electrical Substations.mp4