Lec14 Fuse Protection

8/8/2019 Lec14 Fuse Protection

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
http://goforward/http://find/http://goback/


2/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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


3/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection







Non-Current Limiting FusesCurrent Limiting Fuse



6

Summary


4/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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.


5/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection







Non-Current Limiting Fuses

Current Limiting Fuse



6

Summary


6/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection


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


7/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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.


8/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection

Fuse Characteristics

Thermal Characeristics



9/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection



Current rating.Melting characteristics.



10/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection



Current rating.Melting characteristics.


Voltage rating.

Interrupting rating.


11/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection











6 Summary


12/30

Power System

Protection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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.


13/30

Power System

ProtectionS.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection











6 Summary


14/30


15/30

Power System

ProtectionS.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection

Total Clearing Curve


16/30

Power System

ProtectionS.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection











6 Summary


17/30

Power System

ProtectionS.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


Fuse Protection

Non-Current Limiting FuseExpulsion Fuse

Vacuum Fuse


18/30

Power System

ProtectionS.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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


19/30

Power SystemProtection

S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses


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.


20/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection

Current-Voltage-Time Relationship of Expulsion Fuse


21/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection

1

Abnormality and FaultsAbnormal State



3

Fuse CharacteristicsThermal Characteristics







6 Summary


22/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection


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.


23/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection



24/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



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


25/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection

1

Abnormality and FaultsAbnormal State



3

Fuse CharacteristicsThermal Characteristics







6 Summary

F P t ti


26/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



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.


27/30

F P t ti


28/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



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


29/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



Fuses

Current Limiting

Fuse

Power Class and

Distribution Class

Fuses

Physics of Arc

Interruption

Fuse Protection

Fuse Protection


30/30


S.A.Soman


Abnormal State

Sources of Fault

Current

Introduction toFuse


Thermal

Characteristics

Interrupting

Characteristics



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.

Documents

Lec14 Fuse Protection