this presentation is on the FAULT ANALYSIS AND FAULT MATRIX DEVELOPMENT

1. Presentation By :-KARANSINH M. PARMAR
Subject :- Advanced Power System
Modeling & Simulation
FAULT ANALYSIS
AND
FAULT MATRIX DEVELOPMENT

2. TOPICS
 Introduction
 Causes and Faults
 Types of Faults
 Fundamentals Of Symetrical Components
 Unsymetrical
 References
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3. INTRODUCTION
 A fault in a circuit is any failure that interferes with the
normal system operation.
 Lighting strokes cause most faults on high voltage
transmission lines producing a very high transient that
greatly exceeds the rated voltage of the line.
 This voltage usually causes flashover between the
phases and/or the ground creating an arc.
 Since the impedance of this new path is usually low, an
excessive current may flow.
 Faults involving ionized current paths are also called
transient faults. They usually clear if power is removed
from the line for a short time and then restored.
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4. Cont…
 If one, or two, or all three phases break or if
insulators break due to fatigue or inclement weather,
this fault is called a permanent fault since it will
remain after a quick power removing.
 Approximately 75% of all faults in power systems are
transient in nature. • Knowing the magnitude of the
fault current is important when selecting protection
equipment (type, size, etc..)
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5. Causes and Fault
 General Causes of fault
 Fault due to lightning
 Tree limbs falling on the line
 Wind damage
 Effects of fault
 Flow of excessive current
 Abnormal voltages
 Induces over voltages on neighbouring
equipments.
 Hazards to human, equipment and animals
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6. TYPES OF FAULTS
 Symetrical faults
---Three-phase fault
 Unsymetrical faults
--Single line to ground fault
--Line to line fault
--Double line to ground fault
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FUNDAMENTALS OF SYMMETRICAL
COMPONENTS
 Symmetrical components can be used to transform
three phase unbalanced voltages and currents to
balanced voltages and currents
 Three phase unbalanced phasors can be resolved
into
following three sequences
1.Positive sequence components
2. Negative sequence components
3. Zero sequence components

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 Positive sequence components
Three phasors with equal magnitudes, equally displaced
from one another by 120o and phase sequence is same as that of original
phasors.
 Negative sequence components
Three phasors with equal magnitudes, equally displaced from
one another by 120o and phase sequence is opposite to that of original
phasors.
 Zero sequence components
Three phasors with equal magnitudes and displaced from one
another by 0o
1 1 1, ,a b cV V V
2 2 2, ,a b cV V V
0 0 0, ,a b cV V V

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UNSYMMETRICAL FAULTS
 One or two phases are involved
 Voltages and currents become unbalanced and each
phase is to be treated individually
 The various types of faults are
--Shunt type faults
1.Line to Ground fault (LG)
2. Line to Line fault (LL)
3. Line to Line to Ground fault (LLG)
--Series type faults
Open conductor fault (one or two conductor
open fault)

10. SYMETRICAL FAULT ANAYSIS USING
BUS IPEDANCE MATRIX
 Bus impedance matrix Zbus of a power network can be
obtained by inverting the bus admittance matrix Ybus ,
which is easy to construct.
 However, when the order of matrix is large, direct inversion
requires more core storage and enormous computer time.
 Therefore inversion of Ybus is prohibited for large size
network. Bus impedance matrix can be constructed by
adding the network elements one after the other.
 Using impedance parameters, performance equations in
bus frame of reference can be written as
Ebus = Zbus Ibus
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11. Cont…
 In the expanded form the above becomes
 From this we can write
 From the above, it can be noted that with Iq = 1
p.u. other bus currents set to zero, Ep = Zpq .
Thus Zpq can be obtained by measuring Ep
when 1 p.u. current is injected at bus q and
leaving the other bus currents as zero. In fact p
and q can be varied from 1 to N. 11
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12. Cont…
 From the above, it can be noted that with Iq = 1 p.u.
other bus currents set to zero, Ep = Zpq . Thus Zpq
can be obtained by measuring Ep when 1 p.u. current
is injected at bus q and leaving the other bus currents
as zero. In fact p and q can be varied from 1 to N.
 While making measurements all the buses except one,
are open circuited. Hence, the bus impedance
parameters are called open circuit impedances. The
diagonal elements in Zbus are known as driving point
impedances, while the off-diagonal elements are called
transfer impedances.
 While constructing Zbus using building algorithm,12
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13.  Consider the sample power system shown in Figure
 The network graph of the power system is shown in
figure
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14. Cont…
 The sub-graph consisting of elements 1, 2 and 3
corresponds to a partial network with buses 0, 1 and 2.
In the partial network, if element 4 is added, resulting
graph will be as shown in Figure.
 Now a new bus 3 is created. The added element is a
BRANCH. For the next step, network with elements
1,2,3 and 4 will be taken as partial network. This
contains buses 0,1,2 and 3.
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15. Cont…
 When element 5 is added to this, the network graph
will be as shown in figure
 In this case, no new bus is created and the added
element links buses2 and 3 and hence it is called a
LINK.
 Assume that the bus impedance matrix Zbus, for a
partial network of m buses taking bus 0 as reference, is
known. 15
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16. UNBALANCED FAULT
ANALYSIS USING
BUS IMPEDANCE MATRIX
 Single line to Ground Fault using Zbus
 Consider a fault between phase a and ground through
an impedance zf at bus k
• For a fault at bus k the symmetrical
components of fault current
0 1 2
1 2 0
V (0)
I I I
3
k
k k k f
kk kk kkZ Z Z Z
  
  
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17. LINE TO LINE (LL) FAULT
 Consider a fault between phase b and c through an
impedance zf
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18. DOUBLE LINE TO GROUND (LLG)
FAULT
 Consider a fault between phase b and c through an
impedance zf to ground
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19. BUS VOLTAGES AND LINE
CURRENTS DURING FAULT
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20. References
 www.egr.unlv.edu
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