1. Circuit Breakers & Reclosers

2. Circuit Breaker
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
9/17/2018
Dr.Latif Shaikh

3. Recloser Are types of breakers installed on distribution feeders
Breakers installed in substations are usually referred to as “Power Circuit Breakers”

4. Operating Principle
Circuit Breakers 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 energized and the moving contacts are pulled apart by some mechanism ,thus opening the circuit.
9/17/2018
Dr.Latif Shaikh

5. Simplified Diagram of Circuit Breaker Control
9/17/2018
Dr.Latif Shaikh

6. Electric Arc
9/17/2018
Dr.Latif Shaikh

7. Electric Arc
When contacts of circuit breaker starts separating the contact resistance starts increasing. This increases the I²R (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.
9/17/2018

8. DC Arc Interruption
DC arcs are interrupted by increasing the resistance between the two contacts
This increase resistance is provided by the arc
When this resistance reaches a point where the voltage can no longer maintain the current the arc is extinguished.
Interruption is then complete

9. DC Arc Interruption
Remember with DC there is no current zero before interruption
DC circuit breakers increase in physical size as the voltage rating increases

10. AC Arc Interruption
AC arcs are interrupted by increasing the resistance between the two contacts
This increase resistance is provided by the arc
If the circuit breaker contacts are open at time when the current passes through zero
And the dielectric strength of the medium is built up rapidly so that arc cannot strike again then arc can be extinguished successfully.
Interruption is then complete

11. AC Arc Interruption
Size of AC circuit breaker can be small compared to same voltage DC circuit breaker.
Remember AC arc current reduces to zero two times in each cycle. (2 times)

12. Important Point
Once a fault begins on an electrical system it will not stop on its on.
It must be interrupted by some device.
The uncontrolled flow of current results in the voltage being depressed.
In a few rare instances the current flow may stop if the voltage collapses to zero

13. Important Points In all AC circuit breakers An arc is created
The arc is elongated
The arc is cooled
The current flow stops at one of the zero crossings of the current wave
If enough dielectric then exist between the two contacts a current flow will not be restarted

14. Important Points
The interruption of fault current inside a breaker may be compared to a controlled explosion

15. Omicron Circuit Breaker Testing
ABB SF6 Monitoring
ARC Flash Racking Breaker
Air Blast Breaker Animation
Building 1200 kV Breaker
ABB Disconnecting Circuit Breaker
Line Switch Failure
AEP Energizing 765 kV Breaker
500 kV Disconnect Closing
500 kV Disconnect Opening
Racking GE Magnablast Breaker
ABB Circuit Breaker Show (Don't Do This)
Remote Racking Circuit Breaker

16. Generator Circuit Breaker
Switching Siemens Medium Voltage Switchgear
Toggling Mechanism
Gas insulated Substation
Choosing HV Breakers
Fiber Optic CT
Dawson Mine Flashover
Arc Interruption Animation
Reclosing On To A Fault
345 kV Disconnect Opening
ABB Charging Closing Spring
Contact Resistance
CCVT Failure
CT Testing Metering CT

17. 500 kV Disconnect at Night

18. Grading Capacitors are used in combination with High Voltage Circuit Breakers with different purposes.
Multibreak Circuit Breakers:
Grading Capacitors ensure uniform voltage distribution across all contacts points during normal and switching system operation 
Single break Circuit Breakers:
Grading Capacitors can be used to increase the switching capacity of the breaker
90 up to 300 kV
Sealed construction, maintenance free
All external metallic components made by aluminum or inox steel
High customization range to match CB mechanical and electrical parameters
High mechanical resistance to shock and vibration due CB‘s switching operation
Available in compliance with all international standards

19. Outdoor installation
In air-insulated switchgears (AIS), grading capacitors ensure a uniform distribution of the voltage across the breaking chambers of the live tank circuit breaker.
Grading capacitors for AIS are compliant with standard IEC They are available with a porcelain or a composite insulator. All standard porcelains are equipped with single or alternating long-short sheds and are in full compliance with IEC Maxwell standard fixing is independent of the flange diameter and ensures the interchangeability with old CONDIS® capacitors and the compatibility with the attachment of composite insulators. Other fixing methods are available on request.
The design of High-voltage grading capacitors for AIS is usually customer-specific. Maxwell CONDOR technology offers a high flexibility and will therefore allow for a large customization to meet specific circuit breaker mechanical and electrical needs.