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Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Power System Protection
S.A.Soman
Department of Electrical EngineeringIIT Bombay
Power System Protection
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2/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent Protection
Principle
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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3/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent Protection
Principle
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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4/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Principle of Overcurrent Protection
When the current in a system exceeds a predetermined
value, it indicates the presence of a fault.
Relaying decision is based solely on the magnitude of
current.
Used in radial distribution systems.
Overcurrent relaying and fuse protection uses this
principle.
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Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent Protection
Principle
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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6/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Directional Overcurrent Protection
Uses both magnitude of current and phase angle
information for decision making.
Used in radial distribution systems with source at both
ends.
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7/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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8/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Distance Protection
The basic principle is that the apparent impedance
seen by the relay reduces drastically in case of line
fault.
If the ratio of apparent impedance to the positive
sequence impedance is less than unity, it indicates afault.
This protection scheme is inherently directional.
Impedance relay and Mho relay use this principle.
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Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
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10/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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11/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Principle of Differential Protection
It is based on the fact that any fault within an electrical
equipment would cause the current entering it to bedifferent from the current leaving it.
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12/22
Power System
Protection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Principle of Differential Protection
It is based on the fact that any fault within an electrical
equipment would cause the current entering it to bedifferent from the current leaving it.
By comparing the two currents either in magnitude or in
phase or in both, fault can be determined.
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13/22
Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Principle of Differential Protection
It is based on the fact that any fault within an electrical
equipment would cause the current entering it to bedifferent from the current leaving it.
By comparing the two currents either in magnitude or in
phase or in both, fault can be determined.
It is an attractive option if both the ends of theapparatus are located near each other.
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Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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15/22
Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Differential Protection for Transmission Lines
Its implementation requires a communication channel.
It is extremely accurate.
Its zone is demarkated by CTs.
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Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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17/22
Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Differential Protection for Tapped Line
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18/22
Power System
ProtectionS.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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19/22
Power SystemProtection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Differential Protection for Transformer
CTs are selected in such a way that under normal
conditions the scaled CT currents will match in
magnitude.
Under fault condition, differential current will flow
through the overcurrent relay.Overcurrent relay pick up is set above the no load
current value.
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Power SystemProtection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
1 Overcurrent ProtectionPrinciple
Directional Overcurrent Protection
2 Distance Protection
Principle
3 Differential Protection
Principle
For Transmission Lines
For Tapped LinesFor Transformers
For Busbars
4 Summary
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21/22
Power SystemProtection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Differential protection for Busbar
If the fault is external the algebraic sum of the currents
entering the bus is zero.
If the fault is on the bus the sum is not zero.
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Power SystemProtection
S.A.Soman
OvercurrentProtection
Principle
Directional
Overcurrent
Protection
DistanceProtection
Principle
DifferentialProtection
Principle
For Transmission
Lines
For Tapped Lines
For Transformers
For Busbars
Summary
Protection Paradigms - Apparatus Protection
Summary
Basic Principle of
Overcurrent Protection.Directional Overcurrent Protection.Distance Protection.Differential Protection.
Applications of Apparatus Protection.
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