RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL
SUBSTATIONS OF POWER SYSTEMS
Piao Peng, Zhiwei Liao
School of Electrical Engineering, South China University of Technology, 510640, Guangzhou, China
Fushuan Wen
School of Electrical Engineering, Zhejiang University, 310027, Hangzhou, China
Jiansheng Huang
School of Computing and Mathematics, University of Western Sydney, NSW 2751, Sydney, Australia
Keywords: Digital substation, Fault diagnosis, Root cause analysis, Dempster/shafer theory, Fishbone diagram.
Abstract: The authors present a Cause-Effect fault diagnosis model, which utilises the Root Cause Analysis approach
and takes into account the technical features of a digital substation. The Dempster/Shafer evidence theory is
used to integrate different types of fault information in the diagnosis model so as to implement a
hierarchical, systematic and comprehensive diagnosis based on the logic relationship between the parent and
child nodes such as transformer/circuit-breaker/transmission-line, and between the root and child causes. A
real fault scenario is investigated in the case study to demonstrate the developed approach in diagnosing
malfunction of protective relays and/or circuit breakers, miss or false alarms, and other commonly
encountered faults at a modern digital substation.
1 INTRODUCTION
Fault diagnosis and accident treatment in substations
have become a major challenge of reinforcing power
systems’ safety and reliability. Many integrated
substation diagnosis models and methods have been
proposed to address this challenge by using
information obtained from protective relays and
circuit breakers and employing technologies such as
expert systems (Lee et al., 2000); (Jung et al., 2001);
(Huang, 2002), artificial neural networks (Yang et
al., 1994); (Cardoso et al., 2004), Petri networks
(Huang and Mu, 2006); (Lo et al., 1997), agent
technology (Dong and Xue, 2004), and rough sets
(Hor and Crossley, 2007); (Dong et al., 2002). In
addition, substation diagnosis models and methods
may rely on a single transmission or transformation
equipment as done by the transformer diagnosis
model based on three chromatographic level
correlation analysis (Michel and James, 2005), and
the wavelet theory based transmission line fault
diagnosis model using fault recorders (Silva et al.,
2006). It is observed that the current substation fault
diagnosis models only take into account information
of protective relays and circuit breakers, or fault
features of a single device. In other words, the
existing models and methods, due to employing only
local information, are difficult to diagnose certain
complex faults with uncertainties, including multiple
consecutive failures, malfunctions of protective
relays and/or circuit breakers, missing or false
alarms, and sensor errors, to name a few (Lee et al.,
2000).
With advent of new technologies and tools such
as intelligent primary/secondary equipment and
IEC61850 communication standard, applications of
digital technologies have become the trend in
substation automation, calling for novel fault
diagnosis methods and models with information
sharing and interoperability of intelligent electrical
devices in substations.
In the paper, the authors propose a Root Cause
Analysis (RCA) based Cause-Effect (fishbone
diagram) fault diagnosis model for digital
370
Peng P., Liao Z., Wen F. and Huang J..
RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL SUBSTATIONS OF POWER SYSTEMS.
DOI: 10.5220/0003627403700378
In Proceedings of the International Conference on Evolutionary Computation Theory and Applications (FCTA-2011), pages 370-378
ISBN: 978-989-8425-83-6
Copyright
c
2011 SCITEPRESS (Science and Technology Publications, Lda.)
substations of power systems. The fusion rule of the
well-developed Dempster/Shafer (D-S) evidence
theory is used to integrate different types of fault
information obtained through monitoring states of
substations, protective relays and circuit breakers.
Based on the logic relationship between the parent
and the transformer/circuit breaker/transmission line
child nodes, and between the root and the child
causes, in the diagnosis model, an hierarchical,
systematic, and comprehensive diagnosis can then
be performed. A software package has been
developed to implement the proposed fault diagnosis
model and deployed in Xingguo Substation, the first
digital substation in Jiangxi Province, China.
2 BASIC PRINCIPLES OF RCA
The RCA, originally applied in organization
management (NELMS, 2007), is a hierarchical and
systematic approach to identify and analyse the root
cause, and then develop the countermeasures
accordingly. A large substation comprises many
components with interactions among them. Through
analysing these interactions, a novel fault diagnosis
model for substation transmission and
transformation systems can be built up according to
the structure and data/information flows of a digital
substation. Based on the theory of RCA, the fault
diagnosis model is formulated to explain the linkage
chain of accident causes so that identify what really
happened and the applicable countermeasures.
Figure 1: Framework of RCA-based fault diagnosis
system for digital substations.
The research tools of RCA include Cause &
Effect/Fishbone Diagram, Brain Storm and WHY-
WHY Diagram. There are three types of Fishbone
Diagrams: arrangement-based, cause-based and
solution-based. As shown in Fig. 1, the cause-based
fishbone diagram is adopted to explain the
philosophy of applying the RCA in fault diagnosis
of digital substations. The following is the
explanation to each component of the diagram:
1)
F
: a problem node to be solved as a specified
fault in a substation .
2)
i
c : a child cause of
F
and a basic reason of a
specified fault.
()
i
pc denotes the fault probability
caused by
i
c .
12
() {, , ,}
i
SF c c c
is the set of
child causes which could trig
F
.
3)
j
r : a root cause of
F
and a fundamental reason
of a specified fault in the power system.
(|)
j
i
pr c
denotes the conditional fault probability caused by
j
r
with given
i
c and G(c
i
)={r
1
,r
2
,…,r
j
|c
i
} is the root
cause set.
4)
F
N : the only parent node for the diagnosis
system.
(, ,)
F
NDMO
, composed of three
elements
D ,
M
and O , denotes the basic
diagnosis functions.
D
represents the composition
of the access modes to obtain the required
information from the source
12
{, , , }
en
Ddd d
,
and
e
D is the collection of all the n available modes.
M= {met
1
, met
2
,…, met
p
}, denotes the p fault
diagnosis methods applicable at the node.
{[ , ( )] | ( 1, 2, , )}
ii
Ocpci q
is the diagnosis
output, where
i
cO
, q is the number of the reasons
{
i
c }, and ()
i
pc denotes the fault probability caused
by
i
c .
5)
i
CN and
j
RN : the child nodes and the root
nodes. Like
F
N , they are constituted by the three
elements
D ,
M
, O . Furthermore, they can give a
more detailed diagnosis based on that of
F
N .
Thereinto, S(CN)={CN
1
, CN
2
, …, CN
i
} FN, with
()SCN denoting the set of all the child nodes
belonging to
F
N ; S(RN|CN
k
) ={RN
1
, RN
2
, …, RN
i
}
CN
k
is the set of root node RN belonging to the
child node
k
CN .
6) From the node definition given in 4), it can be
seen that all nodes, including
F
N ,
i
CN and
j
RN
,
are independent in obtaining the information needed
by the diagnosis, selecting the appropriate diagnosis
methods, and analysing fault reasons of each node.
3 FAULT DIAGONOSIS OF
DIGITAL SUBSTATION
A root cause analysis based fault diagnosis system
RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL SUBSTATIONS OF POWER SYSTEMS
371
for digital substations is shown in Fig. 1.
12345
(){ , , , , }SCN CN CN CN CN CN
and
12345
() {, , , ,}SF c c c c c denote the child nodes and the
child causes of transformers, circuit breakers, lines,
bus and secondary system (DC power supply,
network communications and security devices).
3.1 The Modes to Obtain Information
The Substation Configuration Description Language
(SCL) is used to describe the IEC61850 standard
based IED configuration and related parameters,
communication system configuration, substation
system structure, and the relationship among them
for information exchanging. Logical node LN is the
basic function unit of a digital substation to obtain
the needed information. Part of the logic nodes
required in the designed fault diagnosis is listed in
Table 1:
Table 1: Main logic nodes in SCL.
Logical node Explain
1. Pxyz (Protective relay) Protection operation
2. XCBR (Circuit breaker) Switch position
3. RREC (Reclosing) Reclosing operation
4. XSWI (Knife switch) Knife position
5. SMIL (Online monitoring
information of transformer oil
chromatography)
Monitoring value
6. SCBR (Online monitoring
information of circuit
breaker
Monitoring value
For a comprehensive analysis and diagnosis of
an accident, the required diagnosis information
should also include various electrical and chemical
test results of the equipment. The diagnosis
information is divided into three types as following:
1) The location variant information, i.e., the remote
information with time stamps.
2) The section information, including the
information of remote communication and remote
measurement at a certain time point.
3) The data files, including various electrical and
chemical test results of equipment, chemical
experiment results, overhaul history, waveform files
of breaker and recorded faults via on-line
monitoring.
3.2 The Parent and Child Nodes
The information access mode
1
{}Dd of a parent
node
(, ,)
F
NDMO is a passive one in obtaining
location variant information of Pxyz(Protective
relay), XCBR(Circuit breaker), RREC(Reclosing)
and secondary equipment. The diagnosis method M
= {m
1
} based on the optimization algorithm
developed in (Guo, Wen, Liao, Wei, and Xin, 2010),
is to diagnose substation faults with information
obtained from protective relays, circuit breakers and
secondary equipment. The output of the diagnosis is
1122334455
{[ , ( )], [ , ( )],[ , ( )], [ , ( )],[ , ( )]}O cpc cpc cpc cpc cpc
where
1
c ,
2
c ,
3
c ,
4
c ,
5
c respectively denote
transformer faults, malfunction of protective relays
and/or circuit breakers, line faults, bus faults, and
malfunctions of secondary equipment (Fig. 2).
The child nodes such as
1
CN ,
2
CN and
3
CN are
defined below:
1) The child node of transformer
1
CN
The information access mode
12
{}Dd of child
node
1111
(, ,)CN D M O
is an active mode in
obtaining online monitoring information of the
transformer oil chromatography. M = {m
1
} is the
method to analyse the gas in the oil so as to diagnose
transformer faults using the improved three-ratio
method.
11
{[ , ( | )] | 1,2, ,9}
jj
Orprcj
is the
output of the diagnosis, where
1
r is partial
discharge,
2
r is type-1 low-temperature
overheating(below 150
o
C),
3
r is type-2 low-
temperature overheating (150
o
C-300
o
C),
4
r is
medium-temperature overheating,
5
r is high-
temperature overheating,
6
r is low-energy
discharge,
7
r is low-energy discharge and
overheating,
8
r is arc discharge, and
9
r is arc
discharge and overheating.
1
(|)
j
pr c is the fault
probability caused by
j
r
with given
1
c .
2)
The child node of circuit breaker
2
CN
2123
{, , }Dddd
is the information access mode of
child node
2222
(, ,)CN D M O
, and
1
d is a passive
mode in obtaining location variant information of
XCBR,
2
d is an active mode in obtaining online
monitoring information of SCBR,
3
d is an active
FTP mode in obtaining online monitoring waveform
files of circuit breakers. Based on the Dempster’s
Fusion Rule and expert knowledge-base,
M = {m
2
}is
the method to establish the set of state sign with
online monitoring information, including switching
coil current, switch waveform file, storage time of
energy-storage motor, and current curves. The
method diagnoses the faults of circuit breakers
according to the coil switching current RMS and the
FCTA 2011 - International Conference on Fuzzy Computation Theory and Applications
372
elapsed time, the energy-storage motor storage time,
the total distance of a circuit breaker’s operation, the
instantaneous and the average switching speed of a
circuit breaker.
1
d
2
d
3
d
()
ata
D
T
Figure 2: The functional diagram of FN.
22
{[ , ( | )] | 1, 2, ,10}
jj
Orprcj is the output
of the diagnosis,
1
r : mismatch of the switching coil
core and over resistance of switch operation,
2
r :
short circuit of the switching coil,
3
r : burn or break
of the switching coil,
4
r : deformation or
displacement of latch and valve connected to the
core mandrel,
5
r : poor contact and operation of
auxiliary switch and closing contactor,
6
r : fault of
DC power or system auxiliary power,
7
r : fault of
operating mechanism,
8
r : fault of energy-storage
motor,
9
r : mechanical failure, such as deformation
and displacement of linkage unit, and latch failure,
and
10
r : short residual life.
2
(| )
j
pr c denotes the
fault probability caused by
j
r with given
2
c .
3)
The child node of line
3
CN
33
{}Dd is the information access mode of child
node
3333
(, ,)CN D M O ,
3
d is the active FTP
mode to obtain recorded line fault files (Contrade).
M = {m
3
}is the method that utilizes the sudden-
change of the phase current difference to select the
phase and then locate the fault by estimating the
distance with the sampled data from the recorded
fault curve.
32
{[ , ( | )]| 1,2,3, 4}
jj
Orprcj is the
output of the diagnosis, with
1
r as single phase
grounding fault,
2
r as double phase grounding fault,
3
r as inter-phase short circuit fault,
4
r as three
phase short circuit fault.
3
(|)
j
pr c denotes the fault
probability caused by
j
r
with given
3
c . In addition,
the identified fault location is included in the
diagnosis output (Fig. 3).
4 THE FAULT DIAGONOSIS
FLOWCHART BASED ON RCA
As illustrated by the flowchart in Fig. 4, the RCA
based fault diagnosis includes two cases.
4.1 Without Operation of Protective
Relaying, Circuit Breaking and
Reclosing
This case is mainly for monitoring and evaluating
the status of transmission and transformation
equipment. Each child node (
D
,
M
and O ) is
started periodically with a timer interval
int erval
t .
According to the output of child nodes
1
CN ,
2
CN
and
5
CN , the state of transmission and
transformation equipment of the substation is
evaluated, with the evaluation results
1
O ,
2
O ,
3
O ,
5
O and R as given in Eqn. (1).
11
22
1235
33
55
[( | ), ( | )]
[(|),(|)]
[( | ), ( | )]
[(|),(|)]


jj
jj
jj
jj
rc prc
rc prc
RO O O O
rc prc
rc prc
(1)
4.2 With Operation of Protective
Relaying, Circuit Breaking and
Reclosing
The major analysis and diagnosis procedure of this
case is as following:
1)
Once the protective relays, circuit breakers and
reclosers operate, the diagnosis
M of
F
N is started,
to obtain the location variant information of Pxyz,
XCBR, RREC and secondary equipment by mode
1
d . In the diagnosis, the optimization technology is
employed to identify the faulty components and
provide the child cause set of fault as shown in Eqn.
(2).
112 2
334455
( ) {[ , ( )], [ , ( )],
[ , ( )], [ , ( )], [ , ( )]}
SF O c pc c pc
cpc cpc cpc
(2)
RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL SUBSTATIONS OF POWER SYSTEMS
373
2) Due to the lag in acquiring various waveform
files compared with obtaining the location variant
information, a delay of
delay
t is introduced to start
each child node.
3)
To avoid conflicts between the parent node and
child node due to potential errors existing in
information source, the set of all possible faults is
used as the basis of the diagnosis, and each
symptom of faults is used as the evidence in
conducting the comprehensive analyse to the output
of
F
N , O ,
1
O ,
2
O ,
3
O and
5
O . The frame of
discernment is the basic concept of D-S evidence
theory. For a judgment problem, all possible results
that can be recognized are expressed by Θ, a non-
empty set known as the frame of discretion. The
frame consists of a number of mutually exclusive
and exhaustive elements.
12345
{, , , , }qqqqq ,
where
1
q is a transformer fault,
2
q is malfunction of
protective relays and/or circuit breakers,
3
q is a line
fault,
4
q is a bus fault and
5
q is malfunction of
secondary equipment.
If
()
i
mq , the assigned value to function m by
proposition
i
q , meets the following conditions:
0)(
m
(3)
1)(,0)(
i
q
iii
qmqmq
(4)
()
i
mq is known as the basic probability assignment
function (BPAF) of
i
q , which reflects the belief to
the accuracy of
i
q , i.e., the direct support to
i
q but
no support to any subset of
i
q . Furthermore, ()
i
mq
is defined as the focus element of evidence if
i
q is a
subset of Θ and
()
i
mq >0. Φ represents an empty set
in Eqn. (3). Here the diagnosis result of
F
N is taken
as Evidence-1 corresponding to the BPAF
1
()
k
mq ,
and the diagnosis result of
CN is taken as
Evidence-2 corresponding to the BPAF
2
()
l
mq.
1
()
k
mq and
2
()
l
mq are supposed to be the two
BPAF of independent evidence in the same frame of
discernment Θ. While
1
m is the BPAF of Evidence-
1 with
1
() ()
ki
mq pc
,
2
m is the BPAF of Evidence-
2 with
2
() (|)
lji
mq pr c
.
The D-S Fusion Rule is to reflect the joint effect
of the evidences in the same frame of discernment
through calculating a single BPAF with the BPAFs
of different evidences. By applying the rule, the joint
effect of Evidence-1 and Evidence-2 is evaluated in
Eqn. (5).
)()(
)()(
)()(
)(
21
21
21
lk
qq
lk
qqq
lk
qmqm
qmqm
qmqm
qm
lk
lk
(5)
where ()mq is the orthogonal sum of
1
()
k
mq and
2
()
l
mq, denoted by
12
mm m
.
12
12
() ()1
() ()1
k
kl
kl
qql
kl
qq
mqm q
mqm q k




(6)
where
12
() ()
kl
kl
qq
kmqmq

expressing the
conflict degree resulted in the fusion course of the
evidences, and 0
k1. In general, the larger the k,
the more intense conflicts are among the evidences.
Figure 3: The functional diagram of CN.
FCTA 2011 - International Conference on Fuzzy Computation Theory and Applications
374
()
ata
D
T
Figure 4: The RCA based fault diagnosis.
Figure 5: The main connection scheme of the 110 kV Xingguo digital substation.
RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL SUBSTATIONS OF POWER SYSTEMS
375
Table 2: Location variant information obtained by mode
1
d .
Time Alarm ID Alarm value Alarm description
2009-12-20
15:20:12 50ms
PCOS_PZB1H/Q0PTOC3
$ST$Op$general
1
Operation of overcurrent, segment-2, 1
st
time,
limit of high reserve for transformer 1#
2009-12-20
15:20:13 150ms
PCOS_P110LINE1/Q0XC
BR1$ST$Pos$stVal
1 Operation of circuit breaker numbered 111
2009-12-20
15:20:13 260ms
PCOS_PZB1L/Q0XCBR1
$ST$Pos$stVal
1 Operation of circuit breaker numbered 901
2009-12-20
15:20:13 327ms
PCOS_PZB1M/Q0XCBR
1$ST$Pos$stVal
1 Operation of circuit breaker numbered 301
2009-12-20
15:20:13 383ms
PCOS_
P110LINE3/Q0XCBR1$S
T$Pos$stVal
1 Operation of circuit breaker numbered 131
Table 3: Online monitoring information of transformer oil chromatography obtained by mode
2
d .
Time Alarm ID Alarm value Alarm description
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$H2$mag$f 35
Hydrogen measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$CH4$mag$f 12
Methane measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H4$mag$f 15
Ethylene measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H2$mag$f 0
Acetylene measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H6$mag$f 8
Ethane measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$CO$mag$f 406
Carbon monoxide measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$CO2$mag$f 120
Carbon dioxide measurement of
transformer 1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$THC$mag$f 35
THC measurement of transformer
1#(uL/L)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$H2AbsRte$mag$f 1
Absolute gas production rate of
hydrogen of transformer 1#(uL/d)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H2$mag$f 0
Absolute gas production rate of
methane of transformer 1#(uL/d)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H2$mag$f 0.5
Absolute gas production rate of
ethene of transformer 1#(uL/d)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H6$mag$f 0
Absolute gas production rate of
acetylene of transformer 1#
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H6$mag$f 0
Absolute gas production rate of
ethane of transformer 1#(uL/d)
2009-12-20
15:20:23
PCOS_YSP1/Q0SIML0$MX$C2H6$mag$f 0.5
Absolute gas production rate of
THC of transformer 1#(uL/d)
Table 4: The Composite results.
BPAF of nodes
1
q
2
q
3
q
4
q
5
q
1
m
0.4 0 0.6 0 0
2
m
0 0 1 0 0
12
mm m
0 0 1 0 0
FCTA 2011 - International Conference on Fuzzy Computation Theory and Applications
376
Breaker Coil Current and Switch Si
g
nal
 Current
Switch signal
Time (ms)
Current
(
A
)
Figure 6: Coil current and switch signal waveform of circuit breaker numbered 111 obtained by mode
3
d .
Cphasevoltage
Bphasevoltage
Aphasevoltage
Cphasecurrent
Aphasecurrent
Bphasecurrent
Curves
Section
AbsoluteTime
RelativeTime
Secondary
RMS
Figure 7: The fault recording curves of Buxing I line obtained by mode
3
d .
5 CASE STUDY
The developed software package has been applied in
the 110 kV Xingguo digital substation, the first
digital substation in Jiangxi Province, China. The
power outage region due to a fault is circled by the
dotted lines as shown in Fig. 5.
1)
The location variant information is obtained by
mode
1
d (Table II). ()
ata
DT denotes the information
obtained from 2009-12-20 15:20:12 50ms to 2009-
12-20 15:20:13 383ms.
2)
The diagnosis function M of
F
N is started to
identify the faulty components and then provide the
child cause set of the fault
12345
( ) {[ ,0.4],[ ,0],[ ,0.6],[ ,0],[ ,0]}SF O c c c c c
w
hich reveals that the probability is 0.4 for a
transformer fault, and is 0.6 for a line fault.
3)
The online monitoring information of
transformer oil chromatography is obtained by mode
2
d (Table III). The coil current and switch signal
waveform of the circuit breaker numbered 111 is
obtained by mode
3
d (Fig. 6). The recorded fault
curves of Line Buxing I is obtained by mode
3
d
(Fig. 7). A 10s delay
delay
t is set to start the child
nodes
1
CN ,
2
CN ,
3
CN and
5
CN . Finally the root
cause has been identified as a single phase
grounding fault in Line Buxing I
31
{[ ,1]}Or .
RCA METHOD FOR FAULT DIAGNOSIS IN DIGITAL SUBSTATIONS OF POWER SYSTEMS
377
4) According to the D-S Fusion Rule, the diagnosis
result is obtained as given in Table IV:
12
()() 0.410.4


kl
kl
qq
kmqmq
3
12
3
12
() ()
0.6
() 1
() () 10.4
kl
kl
kl
qqq
kl
qq
mq m q
mq
mq m q
Ç=
ǹF
===
-
å
å
Before the fusion, it can be seen that, the parent
node’s supporting is 0.4 to
1
q and is 0.6 to
3
q . The
parent node does not support
2
q
4
q and
5
q . The
child nodes support only
3
q . Once combined, both
of the parent node and the child nodes support only
3
q . The fusion result supports the common part of
the diagnosis results, and discards the conflicting
ones. The fusion result, i.e., the single phase
grounding fault of Line Buxing I, agrees with the
actual fault of the substation.
6 CONCLUSIONS
By taking into account the structure and technical
features of digital substations, the authors develop a
Root Cause Analysis based approach to diagnose
faults of transmission and transformation equipment
of large substations. The D-S evidence theory is
applied to analyse thoroughly the comprehensive
fault information of transmission and transformation
equipment to find the root cause. The developed
fault diagnosis system can be used to diagnose
various faults commonly encountered in substations,
including malfunctions of protective relays and/or
circuit breakers, and miss or false alarms. The
diagnosis system can be implemented in a
hierarchical structure for multi-level information
integration. A real fault scenario was used in the
case study to demonstrate the effectiveness of the
proposed fault diagnosis system. The performance of
the developed software package has been verified by
the case study.
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