SWITCHGEAR AND PROTECTION

A PRESENTATION ON

BY

K.H.Sathya Sameer Mohan. N Nikhil.G.Pai

Shiva Kumar. S Prakash. K

CONTENTS1. INTRODUCTION ON CIRCUIT BREAKERS2. COMMON PARTS OF A CIRCUIT BREAKER3. CLASSIFICATION OF CIRCUIT BREAKERS4. WORKING OF VARIOUS CIRCUIT

BREAKERS5. DESIGN AND SELECTION OF CIRCUIT

BREAKERS6. MANUFACTURERS AND APPLICATIONS

INTRODUCTION ON CIRCUIT BREAKER

Picture: Air Circuit Breaker

GENERAL CIRCUIT BREAKERS

Picture: Miniature Circuit Breaker

INTRODUCTION ON CIRCUIT BREAKER

A circuit breaker is an automatically-operated electrical switch which is designed to protect an electrical circuit from damage caused by overload or short circuit.

Used to prevent the heavy current from damaging power system components.

Unlike fuses, normal operation can be resumed with minimal turn around time.

INTRODUCTION ON CIRCUIT BREAKER

First ever circuit breaker SF6 type circuit breaker in the year 1938 by Germany. Researcher:Vitaly Grosse.

USA developed it in the year 1951.Researchers: Lingal, Browne and Storm.

First industrial application in the year 1953.

INTRODUCTION ON CIRCUIT BREAKER

The Culprit: ArcingSparks jump for several inches in the highly ionized ambient atmosphere. The high current can still damage the circuit.Arcing is analogous to Flash-over in transmission lines.

PARTS OF CIRCUIT BREAKER Frame

Contacts & Operating mechanism

Trip Unit Arc Extinguisher

PARTS OF CIRCUIT BREAKERFRAME

Provides space for mounting the components & holding them in place.

Must withstand mechanical stresses.

Provides insulation & isolation path for current.

PARTS OF CIRCUIT BREAKER

Contacts Provides a method for

connecting the circuit with the system.

Forms a part of the isolation circuit.

BASIC FUNCTIONS Opening Closing

PARTS OF CIRCUIT BREAKEROPERATION: OPENING Spring is generally

used for the purpose.

Opening process is faster.

Spring gets recoiled during Closing Operation.

PARTS OF CIRCUIT BREAKEROPERATION: CLOSING Solenoid is

generally used for the purpose.

Closing process is slower.

Force of attraction increases with reduction in distance.

PARTS OF CIRCUIT BREAKER

TRIP UNIT Opens the circuit

during : 1. Thermal overload

2. Short circuit 3. Ground Fault

PARTS OF CIRCUIT BREAKER

ARCEXTINGUISHER Extinguishes an arc

when contacts are opened.

Circuit Breakers differ Circuit Breakers differ in the type arc in the type arc extinguishers used in extinguishers used in them.them.

PARTS OF CIRCUIT BREAKER

Picture: Creation and elongation of arc

Picture: Splitting of arc

CLASSIFICATION BASED ON OPERATIONAL VOLTAGEI. LOW VOLTAGE CIRCUIT BREAKERS Eg: Air Break Circuit BreakerII. MEDIUM VOLTAGE CIRCUIT BREAKERS Eg: Vacuum Circuit BreakerIII. HIGH VOLTAGE CIRCUIT BREAKERS Eg: SF6 Circuit Breaker

CLASSIFICATIONBASED ON ARC QUENCHING MEDIUM

i. Air Break/Miniature Circuit Breakerii. Oil Circuit Breakeriii. Air Blast Circuit Breakeriv. SF6 Circuit Breakerv. Vacuum Circuit Breaker

CHECK IT OUT

OIL CIRCUIT BREAKERSUB-TYPES Plain-Break Oil Circuit Breaker Self-generated Pressure Oil Circuit Breaker Double Break Oil Circuit Breaker Bulk Oil Circuit Breaker Minimum Oil Circuit Breaker

OIL CIRCUIT BREAKERPlain-Break Oil Circuit

Breaker High current detected

by current sensor. Spring contact opens. Elongation of arc. Formation of gaseous

medium between fixed & moving contacts.

Turbulent motion of the oil,resulting from the gases passing through it.

Picture: Plain Break Oil Circuit

Breaker

OIL CIRCUIT BREAKERSelf-Generated Pressure Oil

Circuit Breaker Plain explosion pot Cross jet pot

Self Compensated pot

Picture: Plain Explosion Pot Oil Circuit Breaker.

OIL CIRCUIT BREAKER

Picture: Cross jet Explosion type Oil Circuit Breaker

OIL CIRCUIT BREAKER

Picture: Cross-jet Explosion Pot type Oil Circuit Breaker

Picture: Self Compensated Explosion Pot type Oil Circuit Breaker

OIL CIRCUIT BREAKERDouble Break Oil Circuit Breaker

Used for high speed arc interruption Employs Intermediate Contacts

Sub Category:1> Axial Blast pot Oil Circuit Breaker

2> Cross Blast pot Oil Circuit Breaker

OIL CIRCUIT BREAKERBulk Oil Circuit Breaker

In this circuit breaker oil is used for both insulation & arc extinguishing purpose.

Requires large amount of oil for its operation.

Advantage: CT can be accommodated in its own body instead of becoming a separate piece.

Disadvantage: Higher the operating voltage more is the Oil required.

OIL CIRCUIT BREAKERMinimum Oil Circuit Breaker

Container for holding the apparatus is made of porcelain.

Has two sections: One containing the contacts Other containing operating mechanism.

Are replaced by SF6 Breakers

AIR BLAST CIRCUIT BREAKER Quenching medium: Compressed air at 20-

30kg/sq.cm Uses Switching resistors and equalizing

capacitors Switching resistors: reduces transient over

voltages Equalizing capacitors: To equalize voltage

across breaks Categorized as: Cross blast Circuit Breakers Axial blast Circuit Breakers

AIR BLAST CIRCUIT BREAKER

Picture: Cross Blast Circuit Breaker

AIR BLAST CIRCUIT BREAKER

Picture: Single Blast type axial-blast Circuit Breaker

Picture: Double Blast type axial- blast Circuit Breaker

AIR BREAK CIRCUIT BREAKER Quenching medium: Air at atmospheric

pressure

Suitable for high current interruption at low voltage

Principle of high resistance is used for arc interruption

AIR BREAK CIRCUIT BREAKER

SF6 CIRCUIT BREAKERABOUT SF6(sulphur hexafluoride) Specialty: inert, non-toxic, non

flammable heavy gas. High dielectric strength(2.5 times

that of air)

Disadvantage: Decomposes at high temperature.

With moisture, it may spoil the parts of CB.

Sub categories: Double-pressure SF6 Circuit breakers

Early type of SF6 Circuit breaker

Puffer type Circuit Breakers

Uses SF6 in a compressed form

SF6 CIRCUIT BREAKER

SF6 CIRCUIT BREAKER

Picture: Closed position (Working condition)

SF6 CIRCUIT BREAKER

Picture: Closed Position (Operation stopped)

VACUUM CIRCUIT BREAKER Arc Quenching medium: High Vacuum

Air at a pressure of 10-5 mm & below is called High Vacuum.

An arc formed at a small separation of 1cm can also be extinguished efficiently.

Contacts made of special materials.

VACUUM CIRCUIT BREAKER

Picture: Vacuum type circuit Breaker

VARIOUS STANDARDS

Picture: Standards used in various parts of the world

DESIGN OF CIRCUIT BREAKER

Finalizing basic data and specifications.Choice of circuit breakerPreliminary design of arc extinguishing mediumCalculation of insulating system of the circuit breaker

DESIGN OF CIRCUIT BREAKER

BASIC DATA AND SPECIFICATIONS

Nominal voltageNominal currentFault CurrentRupturing capacityTime of operationAllowable temperature

rise.

Highest closing current.Time of closing.Type of location of installation.

SELECTION OF CIRCUIT BREAKERS

TYPE ARC QUENCHING MEDIUM

VOLTAGE RANGE & BREAKING CAPACITY

Miniature Circuit Breakers

Air at atmospheric pressure

400-600V;Small current rating

Air-Break Circuit Breakers

Air at atmospheric pressure

400V-11KV;5-750MVA

Minimum Oil Circuit Breakers

Transformer Oil 3.3-220KV;150-25000MVA

Vacuum Circuit Breakers

Vacuum 3.3-33KV;250-2000MVA

SF6 Circuit Breakers SF6 at 5kg/cm2 pressure

3.3-765KV;1000-50000MVA

Air Blast Circuit Breakers

Compressed air at high pressure(20-30 kg/cm2)

66-1100KV;2500-60000MVA

SELECTION OF CIRCUIT BREAKERS

RATED VOLTAGE CHOICE OF CIRCUIT BREAKERS

REMARK

Below 1 KV Air- break C B

3.3-33KV Vacuum C B, SF6 C BMinimum C B

Vacuum preferred

132-220KV SF6 C B, Air Blast C B,Minimum Oil C B

SF6 preferred

400-760KV SF6 C B, Air Blast C B

SF6 preferred

DESIGN OF CIRCUIT BREAKER

Basic Design of Arc Extinguishing Chamber

Calculation of arc Voltage. Analysis of process of gas formation

during arcing. Calculation of pressure inside the chamber Velocity of motion of gases formed in the

chamber.

DESIGN OF CIRCUIT BREAKER

Insulation Design

Choice and calculation of various clearances to be provided.Calculation of voltages that appear across the gaps.Calculation of minimum insulation to be provided for current carrying parts.

APPLICATIONS OF CIRCUIT BREAKER

UPS Equipment Power Supplies Small Generators Entertainment Systems Vending Machines Office Machines Telecom Power Distribution Railway Signaling Systems

APPLICATIONS OF CIRCUIT BREAKER

Power conversion systems Automatic control systems Generator sets AC and DC Branch Circuit Protection

MANUFACTURERS OF CIRCUIT BREAKER

ABB ALSTOM MOELLER INDIA AREVA L&T HAGER