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1/30
Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Power System Protection
S.A.Soman
Department of Electrical EngineeringIIT Bombay
Fuse Protection
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting FusesCurrent Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6
Summary
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting FusesCurrent Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6
Summary
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Abnormal State
Pertains to deviation from the rated operating point.
Operation in this state for a long time can lead to
damage of the equipment.
It is also unsafe to operate in this region.
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6
Summary
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6/30
Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Sources of Fault Current
In a radial system with single source, the magnitude of fault
current depends upon the following:
Source contribution.
Transformer impedance.
Motor contribution
Distance of fault from the source.
The transformer short circuit current is given by,
Isc = Transformer Full Load Current100
%Z
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Introduction to Fuse
A fuse is a device that opens a circuit with a fusible part
which is heated and severed by current flowing through it.Its
operation involves two phases.
Melting of the fuse element when the current has large
enough magnitude.Current interruption when the arc stuck is de-ionized.
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Fuse Characteristics
Thermal Characeristics
Interrupting Characteristics
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Fuse Characteristics
Thermal Characeristics
Current rating.Melting characteristics.
Interrupting Characteristics
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Fuse Characteristics
Thermal Characeristics
Current rating.Melting characteristics.
Interrupting Characteristics
Voltage rating.
Interrupting rating.
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6 Summary
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Power System
Protection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Thermal Characteristics
The melting time of fuse
is inversely proportional
to the square ofmagnitude of current.
This relationship is given
by its melting time
current characteristics.Fuse has very inverse
time current
characteristics.
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Power System
ProtectionS.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6 Summary
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15/30
Power System
ProtectionS.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Total Clearing Curve
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Power System
ProtectionS.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
1 Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3 Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6 Summary
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17/30
Power System
ProtectionS.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Non-Current Limiting FuseExpulsion Fuse
Vacuum Fuse
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Power System
ProtectionS.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Non-Current Limiting Fuse
Expulsion Fuse
It is used in overhead circuits and equipments whereexpulsion gases causes no problem.Due to high temperature of the arc, special gas
generating materials like fiber, melanine,boric acid, oiletc rapidly create gases.These gases help to reduce the arc channel anddeionize the arc.This leads to rapid build up of dielectric strength thatcan withstand the transient recovery voltage.
Vacuum Fuse
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of ArcInterruption
Fuse Protection
Non-Current Limiting Fuse
Expulsion Fuse
It is used in overhead circuits and equipments whereexpulsion gases causes no problem.Due to high temperature of the arc, special gas
generating materials like fiber, melanine,boric acid, oiletc rapidly create gases.These gases help to reduce the arc channel anddeionize the arc.This leads to rapid build up of dielectric strength thatcan withstand the transient recovery voltage.
Vacuum Fuse
Its design, operation and current-voltage-timecharacteristics are similar to that of expulsion fuse.It is a completely sealed unit.
There is no expulsion action.
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Current-Voltage-Time Relationship of Expulsion Fuse
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
1
Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3
Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6 Summary
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Current Limiting Fuse
The basic principle is to insert a high resistance in the
fault circuit which is otherwise inductive.
This makes zero crossing of current and voltage in
phase.
Thus temporary arc is extinguished and dielectric
medium will be quickly deionized.
The fusible element used is very long and surroundedby silica sand.
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Current Limiting Fuse
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Current-Voltage-Time Relationship of Current Limiting Fuse
F P i
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
1
Abnormality and FaultsAbnormal State
Sources of Fault Current
2 Introduction to Fuse
3
Fuse CharacteristicsThermal Characteristics
Interrupting Characteristics
4 Classification of Fuses
Non-Current Limiting Fuses
Current Limiting Fuse
Power Class and Distribution Class Fuses
5 Physics of Arc Interruption
6 Summary
F P t ti
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Classification Based on Domain of Application
Power class fuses which are used in or near togenerating station or substation for three phase circuits.
Distribution fuses have specifications closely matching
to distribution system and are away from source or
substation on a single phase or a three phase system.
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F P t ti
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
From the equation it can be seen that
The current is proportional to the area under the
difference of source and arc voltage.
A higher source voltage will adversely affect the
interruption of current.
A high fuse arc voltage will help in limiting the fault
current.
The fuse arc voltage sustained over a time has a
positive impact on limiting fault current.
Lower the inductance, higher the available prospective
fault current.
Fuse Protection
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Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Fuse Protection
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30/30
Power SystemProtection
S.A.Soman
Abnormalityand Faults
Abnormal State
Sources of Fault
Current
Introduction toFuse
Fuse Charac-teristics
Thermal
Characteristics
Interrupting
Characteristics
Classificationof Fuses
Non-Current Limiting
Fuses
Current Limiting
Fuse
Power Class and
Distribution Class
Fuses
Physics of Arc
Interruption
Fuse Protection
Summary
Abnormality and faults.
Sources of fault currents.Fuse for overcurrent protection.
Characteristics of fuse.
Classification of fuse.
Physics of arc interruption.
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