In this presentation, we’ll describe types of fault in power system including : Definition of Fault in Power System Types of Fault and A short description of various types of Fault

1. POWERSYSTEM
ANALYSIS
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PSA

2. FAULTSIN
POWERSYSTEM
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PRESENTATION ON

3. • In this presentation, we’ll describe types of
fault in power system including :
• Definition of Fault in Power System
• Types of Fault and
• A short description of various types of Fault
3
Index
A short description of fault in
Power System.
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4. Definition of Fault in Power System
Fault in Power System
• The fault in power system is the abnormal
condition of the electrical system which damages
the electrical equipment and disturbs the normal
flow of the electric current.
• A fault is occur, when two or more conductors
that normally operate with a potential difference
come in contact with each other.
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Figure (1.0) : Various fault in Power System
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5. 1. Symmetrical Fault :
• That fault which gives rise to
symmetrical fault currents is called
a symmetrical fault.
• The most common example of
symmetrical fault is when all the
three conductors of a 3-phase line
are brought together simultaneously
into a short-circuit condition.
Figure (1.1) : Symmetrical Fault
Types of Fault
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The faults in a 3-phase system can be classified into two main categories :
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6. Description of Symmetrical fault:
Symmetrical Fault :
• Balance current Flow ; Ia = Ib = Ic ,With same
phase (120o) angle.
• Line voltage tends to zero ; Va = Vb = Vc ≈ 0
• At this reason line impedances (Z≈0) also be zero.
• Excess current flow occures conductors
overheated, overheat can melt the conductor.
• It can be causes the total shutdown of power
system.
• This fault is the most severe fault in power
system.
• Hopefully, it can not be happen as per usual, less
than 5% fault of power system are balanced
fault.
Figure (1.1.1) : Symmetrical Fault
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7. 2. Unsymmetrical Fault :
• Those faults which give rise to
unsymmetrical currents is known
as unsymmetrical faults. The
unsymmetrical faults may take one
of the following forms :
• Single line-to-ground fault
• Line-to-line fault
• Double line-to-ground fault
Figure (1.2) : Unsymmetrical Faults
Types of Fault
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8. Description of Various Unsymmetrical faults:
i. Single Line to Ground Fault :
• A single line-to-ground fault on a transmission
line occurs when one conductor drops to the
ground or comes in contact with the neutral
conductor.
• Such types of failures may occur in power system
due to many reasons like high-speed wind, falling
off a tree, lightning, etc.
Figure (1.3) : Single Line to Ground Fault
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9. Description of Single Line to Ground fault:
Single Line to Ground Fault :
• Most amount of current hass been flow through
the fault (Ia) line.
• Line voltage (Va ≈ 0) and impedance (Za ≈ 0) of
fault line tends to zero.
• Other line currents (Ia & Ib) also tends to be zero.
• Most of the fault of overhead line is single line to
ground fault.
• This type of fault occures a huge power loss of
power system.
• In transmission line faults, roughly 65% - 70% are
asymmetric line-to-ground faults.
Figure (1.3.1) : Single Line to Ground Fault
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10. Description of Various Unsymmetrical faults:
ii. Line to Line Fault :
• A line to line fault occurs when two conductors
are short circuited.
• The line to line faults occur when two conductors
make contact with each other mainly while
swinging of lines due to winds.
Figure (1.4) : Line to Line Fault
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11. Description of Line to Line Fault:
Line to Line Fault :
• The fault current is flow between two lines (Ib
and Ic).
• It causses a circulatiing current flow between
them.
• The other line current (Ia≈ 0) tends to be zero.
• Voltages (Va & Vb) and impedances of fault lines
also equal to zero.
• Line to line fault occures rearly in transmission
line, most of this type of fault happens in
household equipment e.g motor, IPS etc.
• About 5- 10 percent of the faults are this type. Figure (1.4.1) : Line to Line Fault
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12. Description of Various Unsymmetrical faults:
iii. Double Line to Ground Fault :
• Double line to ground fault occurs when any two
phases of the power circuit is short circuited to
ground or neutral.
• The double line to ground faults occur when two
conductors make contact with each other and
short with earthing line due to heavy storm or
fall of tree.
Figure (1.5) : Double Line to Ground Fault
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13. Description of Double Line to Ground Fault:
Double Line to Ground Fault :
• Double line to ground fault is also same as the
line to line fault.
• But there is a difference from L-L fault, that, the
fault line is grounded.
• Here, Ib and Ic carries the fault current, where the
net impedance of two lines are zero.
• Another line (Ia) can not carry any current.
• This type of fault can unstabe the power system
and this reason electrical and mechanical
equipment can goes to out of service.
• As usual of L-L fault, Double line to ground fault
also occures rearly.
• About 1-5% fault of power system are Double
Line to Ground Fault.
Figure (1.5.1) : Double Line to Ground Fault
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14. 1430 July, 2020

15. • Principles of Power System – V.K Mehta
• A Textbook of Electrical Technology (Volume III) -
B.L.Theraja
• Wikipedia – www.wikipedia.org/electric_fault
• Electrical Academia – www.electricalacademia.com
Picture Credit :
• Circuit Globe – www.circuitglobe.com
15
References
Where we got Everything.
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16. THANKYOU
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