Volume 54, Number 3-4, 2013
243
Hardware-software Application for
Monitoring and Diagnosis of Circuit
Breakers
Mihai ANDRUŞCĂ, Maricel ADAM, Razvan PANTELIMON, Adrian
BARABOI, Cătălin PANCU
Abstract: A method to diagnose circuit breakers is presented, which allowed accurate diagnosis of the monitored equipment, based
on the comparison of collected data with a similarly recording for detect possible anomalies, respective information on the kind of
fault. This paper presents a monitoring and diagnosis system for circuit breakers. Advanced processing and data analysis was
performed by using a software application developed in LabVIEW programming environment. A wavelet algorithm was applied to
acquired signals during circuit breaker operations for denoising and detrend the signals. The method can predict the early failure,
for maintenance of faulty components in order to reduce costs and improve quality in the electric service.
Keywords: monitoring, diagnosis, software application, wavelet transform, circuit breaker.
1.
INTRODUCTION
During operation, electrical equipment (circuit
breakers) is subjected to mechanical, thermal and
electrical stresses. To avoid some faults in their
incipient phase, it is important to monitor the relevant
parameters which characterize the technical condition
of the equipment. This field of research is in continuous
expansion having as a final objective to implement
some monitoring system for reduce the required time
for testing the circuit breaker, to achieve direct results
of the measurements, to compare these results with
previous records, to provide a large quantity of
information, to have the possibility to test circuit
breaker on-line.
Introduction of a large number of circuit breaker
parameters for monitoring and finding the best method
for establish the diagnosis are important research
directions in this area.
In this paper is presented a fault diagnosis method
by means of detects specific changes in acquired
parameters from a fingerprint recording, based on
differences between values and curves of those
parameters. If it is exceeded a predetermined limit
value it indicates that one of the characteristics of the
circuit breaker is in an unacceptable range.
In the paper is described a hardware-software
structure and parameters for monitoring and diagnosis
of the circuit breaker condition (operative voltage,
currents through solenoid coils, travel of contact mobile
etc.), and also a software application which is used for
advanced processing and analyzing the obtained data.
Finally, the experimental tests were performed
on a circuit breaker having different abnormal
situations that could have place on exploitation: faults
in solenoids, low, respective high operative voltage etc.
The analyzed circuit breaker was of medium
voltage with oil which has the operating mechanism
with springs accumulated energy.
Abnormal situations encountered in the
operation of this circuit breaker type that use
accumulated energy in springs can be generalized to
any type of medium, respectively high voltage circuit
breakers, with this kind of operating mechanism (SF6,
vacuum).
2.
FAULTS, PARAMETERS AND
TECHNIQUES FOR CIRCUIT BREAKERS
MONITORING AND DIAGNOSIS
Researches performed by experts in the field of
circuit breakers monitoring, indicate that over three
quarters of major (FM), respectively minor faults (Fm)
are of mechanical nature due to operating mechanism
and of electrical nature due to auxiliary control circuits,
as in Table 1, [1], [2] and [3].
These statistics represent a starting point for
design and development of embedded systems for
monitoring and diagnosis of circuit breakers.
No.
crt.
1
2
3
4
5
Table 1. Faults distribution of circuit breakers
Faults type
FM
Nature and manifestation place
(%)
Mechanical in operating mechanism
40
Mechanical in other parts of circuit breaker
11
Electrical in main circuit
12
Electrical in control and auxiliary circuits
28
Other faults
9
© 2013 – Mediamira Science Publisher. All rights reserved.
Fm
(%)
40
11
1
11
37
244
ACTA ELECTROTEHNICA
Monitoring is the continuous process of gathering
relevant information about the monitored equipment
while diagnosis is a process that uses information
obtained during monitoring in order to verify if the
measured values are in accordance with those specified
by the manufacturer or with some records determined
previously according to which alerts, alarms,
recommendations are emitted.
Thus, diagnosis is the next step representing the
interpretation of on-line and off-line data measured.
Monitoring is the basis of diagnosis, but without a
diagnosis, the measured data would not have the same
value.
Monitoring and diagnosis of circuit breakers is
orientated on function or/and subassembly (operating
mechanism, auxiliary and control circuits, switching
function, insulating). In Table 2 are presented the
parameters and techniques used in monitoring and
diagnosis of operating mechanism, respective auxiliary
and control circuits of circuit breakers.
Table 2. Parameters and techniques for monitoring and diagnosis
Function/
Parameter
Techniques and
Subassembly
device
Acting number
Counters
Operation time
Accumulated
energy
Operating
mechanism
Auxiliary and
control
circuits
Recording opening / closing time in
the primary circuit. Special sensors.
Oil pressure, nitrogen pressure,
micro-switches position
Kinematics
Magneto-resistive position sensor,
characteristics potentiometer, bar codes technique
etc.
(travel, velocity)
Motor condition Current, voltage and temperature of
motor, the number of pump starts,
pump recharging time, pump
operating total time
Vibratory
Fourier transform, the frequency
fingerprint
spectrum and peak frequency.
Accelerometers.
Operative
Voltage sensor
voltage
Current through
Current duration and evolution.
coil
Shunts, current transformer etc.
Circuits
continuity
Continuity verification by passing a
small current or in impulse
Auxiliary
contacts status
Verify the integrity by sequence of
the operation, position etc.
Those components are responsible for the largest
number of faults. Embedding a large number of these
parameters, it will allow a more accurate report of the
real technical condition of equipment, [3], [4] and [5].
New tendency in circuit breakers maintenance is
to pass from the maintenance based on predetermined
criteria through maintenance based on condition, which
involves introduction of embedded systems for
monitoring and diagnosis of their technical condition,
[3] and [6].
3.
HARDWARE-SOFTWARE SYSTEM FOR
MONITORING AND DIAGNOSTIC
The intelligent system of monitoring and
diagnostic (SIMDE) of electrical equipment it uses for
monitoring and diagnostic of circuit breakers from high
and medium voltage electrical installations with onephase and three-phase operation, [6], [7].
The system can be installed on new circuit
breakers as well as on existing circuit breakers and
allows to obtain information necessary to establish their
technical state.
The monitoring and diagnostic system can be
mounted in the enclosure of operating mechanism or
attached on it introducing the system into an exterior
enclosure, and it connects in parallel with operating
circuits of circuit breaker. On duration of a trip or
closing operation of circuit breaker, the system allows
to acquisition of the following information about it:
- main currents on each phase;
- currents through the trip and closing coils;
- the displacement of mobile contact;
- operating voltage;
- status of circuit breaker;
- sulfur hexafluoride (SF6) pressure;
- motor starting of operating mechanism;
- the behaviour of motor protection;
- contacts electroerosion;
- other 3 analog signals having the range 0-10 V
DC, established by the user.
The same information can be acquired also in the
case of some multiple operations like as rated operating
sequence: O-0,3 s-CO-3 min.-CO.
The records realised by SIMDE after a trip/closing
operation of circuit breaker are sent to PC (through
direct connection, GSM modem or SD card) where are
analysed, with the help of an adequate software,
through comparison with the results of some similar
records, and also with the limits anterior programmed.
If a limit is exceeded then an alarm signal is released
which indicates the fact that one of the circuit breaker’s
features is into an unacceptable range.
The main technical features of hardware-software
system are:
- 3 AC channels, galvanic insulated, dedicated to
measure the main currents through the current
transformers (the load is maximum 0,01 VA);
- 13 DC channels, galvanic insulated, dedicated to
measure the currents through the trip and closing coils,
the operating voltage and the displacement of the
mobile contacts (shunts resistance: 0,2 Ω (5 A), 0,1 Ω
(10 A), 0,05 Ω (20A));
- 12 digital inputs galvanic insulated, having:
6 channels with one of the following ranges 3-7 V,
or 20-60 V, 80-150 V with exterior resistor, the
voltages being in DC or AC;
6 channels with ranges 170-250 V DC or AC;
- 9 outputs of relay type having contacts NO/NC
with features 5 A at 30 V DC, or 5 A at 250 V AC;
- serial interfaces:
Volume 54, Number 3-4, 2013
-two asynchronous interfaces on RS232
transceiver;
-one serial interfaces having TTL logic signals;
-one module UART 16C550 for GSM
communication;
- SD card with storage memory of 2 GB;
- alphanumeric display LCD 4x20 characters or
graphic display LM24014H;
- keyboard with 4 keys;
- recording: sampling rate 2 kHz;
- external SRAM memory of 1Mb;
- EEPROM memory of 512Ko;
- triggering of data acquisition: the state changing
of any digital inputs;
- heating resistance (optional);
- voltage supply: 85-265 V AC; 110-330 V DC;
- operating temperature: -20 °C ... +40 °C.
The Figure 1 shows the block diagram of
monitoring and diagnostics system, structure realised
with the help of the microcontroller ATMEL
ATmega2560 AVR.
4.
245
EXPERIMENTAL INSTALLATION
In Figure 2 is presented the electrical diagram
used for monitoring and diagnosis of medium voltage
circuit breakers from medium voltage installation. This
includes: a circuit breaker, respectively a monitoring
and diagnosis system consists of sensors/transducers
and dedicated hardware-software structure.
Circuit breaker, on which data were acquired for
diagnosis is with springs operating mechanism.
During of closing/closing operations of circuit
breaker, the system allows to acquire of following
information about it:
- main currents on each phase;
- currents through the trip and closing coils;
- travel of mobile contacts;
- operating voltage.
To determine the travel is used a resistive sensor
(potentiometer) which is reliable and easy to use,
ensuring accurate precision. Resistive sensor was
attached to a mobile part of the movement transmission
system from the operating mechanism to mobile
contacts of circuit breaker.
Fig.1. Block diagram of system
246
ACTA ELECTROTEHNICA
Fig. 2. Electrical diagram of monitoring and diagnosis system for circuit breaker
5.
SOFTWARE APPLICATION
For an easy interface with the users, a software
application was developed in LabVIEW programming
environment, [8].
In Figure 3 is represented the architecture for
monitoring and diagnosis system of circuit breakers and
also the software application structure.
After acquire some parameters of circuit breakers
with monitoring and diagnosis system, the acquired
data are transmitted to a PC, where are subject to a
process for processing, analyzing data, visualization in
graphical form of signals etc.
The software application algorithm developed
offers the following features, [7]:
- initialization of the application;
- uploading data for analysis;
Phase currents
Circuit breakers
Monitoring of current through coils of closing,
respectively opening solenoid is performed with shunts.
Acquisition of the 3-phase currents is achieved with
current transformers, and also for operative voltage is
used a voltage sensor.
Recordings performed with hardware-software
structure
for
monitoring
at
the
connection/disconnection of the circuit breaker are
transmitted to a computer (through direct connection,
GSM modem or SD card) where are analyzed using an
adequate software, by comparing with the results of
similar records, as well as previous limits by
programming. In the case when data are transmitted on
the memory card of SD type, the monitoring system
performs their automatic save after acquisition.
The signal acquisition was performed at a
sampling rate of 2 kHz, with a resolution to 12 bits,
while the recorded signal duration was 260 ms.
Operative voltage
Currents through
solenoids coil
Travel of mobile
contacts
Acquired Upload data
data
Intelligent
System for
monitoring
and diagnosis
of electrical
equipment
Data Reading
LabVIEW
software
application
Calculate monitored
parameters
Data processing
Values and curves
visualization
Data analysis
Alarms,
Warnings
Reports
Fig. 3. Monitoring and diagnosis system of circuit breakers and
software application structure
- calculate and display the monitored parameters
in different graphs or in the same graphs for an easy
interpretation;
- extracting the characteristic values of the
parameters (minimum, maximum etc.);
- processing and analyzing data;
- generate the alarms and reports.
In Figure 4 is presented the front panel of software
application that allows uploading the files, both from
normal situation and abnormal situation, visualizations
the values and curves of obtained data for analyzing
them, [9].
Volume 54, Number 3-4, 2013
By compare obtained curves and values of the
parameters on the circuit breaker operation in abnormal
situations, with the parameters considered normal it can
observe the difference between those signals.
In Figure 5 is presented a part of block-diagram of
the software application, namely the diagram of the
subprogram for determination the travel, respective the
velocity of mobile contacts.
This part of diagram performs:
- reading data from the corresponding column for
travel of mobile contacts from both saved files current
and that considered normal;
- removing the offset;
- transforming the rotary motion of the
displacement transducer into the linear motion of
mobile contacts;
- performing the signal denoising and detrending;
- extracting the minimum and maximum value of
the travel of mobile contacts;
Fig. 4. Front panel of monitoring and diagnosis system for circuit
breaker
247
monitored parameters (maximum, minimum, average
etc.), graphical visualization etc.
An advanced software component developed by
wavelet algorithms for signal processing was designed
and implemented in order to extract information from
the acquired parameters.
The data analysis, in accordance to variable scales
in the time and frequency domain, constitutes the basic
idea to use the Wavelet theory. The Wavelet Transform
(WT) is a mathematical tool for signal analysis.
Wavelets are functions that are used to decompose
signals. The WT presents local representations in the
time and frequency domain of a given signal, [10] and
[11].
One of the most effective application of wavelets
in signal processing is denoising, or reducing noise in a
signal. The wavelet transform-based method can
produce much higher denoising quality than
conventional methods. Furthermore, the wavelet
transform-based method retains the details of a signal
after denoising, [12].
For applications that require signal reconstruction,
the LabVIEW Wavelet Analysis Tools provide the
following wavelet transforms tools:
- Discrete wavelet transforms (DWT);
- Undecimated wavelet transforms (UWT).
Also, the Wavelet Analysis Tools provide the
following commonly used discrete wavelets:
- Orthogonal wavelets - Haar, Daubechies (dbxx),
Coiflets (coifx), and Symmlets (symx);
- Biorthogonal wavelets - FBI, and Biorthogonal
(biorx_x);
where x indicates the order of the wavelet, the
higher, the order, the smoother of wavelet. Orthogonal
wavelets are suitable for applications such as signal
denoising.
Fig. 5. Part of block diagram of monitoring and diagnosis system for
circuit breaker
- derivation the signal of the travel of mobile
contacts to obtain the velocity of mobile contacts;
- extracting the maximum velocity;
- graphical visualization of the acquired
parameters.
Regarding the other parameters acquired by the
monitoring system (operative voltage, phase currents,
currents through opening and closing coils) are subject
to the same process of signal processing, namely:
reading data from files, performing the signal
denoising, extracting the characteristic values of
Fig. 6. Phase R current with noise and the denoised signal using the
wavelet transform-based method.
248
ACTA ELECTROTEHNICA
In Figure 6 is presented the denoising case of
phase R current signals. It can see the original signal
obtained with monitoring system with noise, respective
the denoised signal with UWT, respective DWT. The
denoising result of the UWT has a better balance
between smoothness and accuracy than the DWT. For
better denoising, in developed software application it
was used the UWT.
The wavelet type used for denoising was
Symmlets (sym8). The functions WA Detrend, WA
denoise and Wavelet Denoise Express from LabVIEW
Advanced Signal Processing toolkit was used, [12]. The
Wavelet Denoise Express enables to specify parameters
and settings for an analysis, to select the wavelet type,
specify a threshold and visualization the results
immediately.
6.
EXPERIMENTAL RESULTS
In Table 4 are presented the circuit breaker
condition, possible causes of abnormal situation,
respective the nature and manifestation place.
Table 4. Circuit breaker conditions
No
crt.
Circuit breaker
condition
1
2
Normal condition
Abnormal condition,
circuit
low voltage in
interruption, the
auxiliary circuit
occurrence of
short circuits on
the solenoid coils
or relay
Abnormal condition, circuit interruption
high voltage in
auxiliary circuit
Abnormal condition, incorrect settings,
low or high
respectively
changes in
accumulated energy
in springs
physical properties
of springs
Abnormal condition,
inadequate
low or high free
adjustment of
solenoids
travel of solenoid air
gap
Abnormal condition, lack of lubrication,
low or high current operative voltage
of solenoids
out of range
3
4
6
7
On a circuit breaker have been simulated various
types of faults that could occur in exploitation and with
the help of the software application for monitoring
and diagnosis of circuit breakers described above, it can
observe the variations of acquired parameters.
In Table 3 are presented some parameters
considered for diagnosis and their variation range in
order to establish circuit breakers technical condition.
Table 3. Parameters considered for monitoring and diagnosis of
circuit breakers
Range
No.
Considered parameters
Unit
crt.
Minim
Maxim
1
Current through opening
A
0.7
0.8
solenoid coil
2
Current through closing
A
0.7
0.8
solenoid coil
3
Opening coil current
A·s
0.55
0.63
profile area
4 Closing coil current profile
A·s
0.55
0.63
area
5
Mean operative voltage
V
210
220
6
Travel of contact mobile
mm
211
218
7
Opening velocity of
m/s
4.5
6
contact mobile
8 Closing velocity of contact
m/s
3.7
5.2
mobile
9
Opening time
ms
44
70
10
Closing time
ms
93
123
Possible causes of
abnormal situation
8
Other abnormal
condition
transducers
incorrect mounting
Nature and
manifestation
place
electrical faults in
the control and
auxiliary circuit
electrical faults in
the control and
auxiliary circuit
mechanical faults
in operating
mechanism
electrical faults in
the control and
auxiliary circuit
(fault in solenoid)
mechanical or
electrical faults in
the control and
auxiliary circuit
fault in transducers
Further, the cases which were selected for
presenting are:
- electrical faults in the control and auxiliary
circuit: faults in solenoid.
- faults on travel transducer.
6.1. Solenoid faults
Monitoring the current through solenoid coil
provides information on start time and end time of
mobile armature movement and also on start time of
open the auxiliary contacts. From changes of coil
current timings can be deduced the occurrence of some
problems (lack of lubrication, inadequate adjustment of
solenoids) in control system of the operating
mechanism, [4].
Ib (A)
0.9
A
C
0.7
0.5
B
The proper analyses of these parameters may
identify some abnormal situations in circuit breaker
operation; respective may detect a fault of the circuit
breaker.
If the value of one or more of the presented
parameters in Table 3 exceeds the allowable limits it
indicates that one of the circuit breaker characteristics is
into an unacceptable domain.
0.3
0.1
0
20
40
60
80
Time (ms)
Fig. 7. Evolution of current through opening coil
249
Volume 54, Number 3-4, 2013
In Figure 7 is given the current evolution from
opening coil recorded for a 24 kV circuit breaker with
spring-operated mechanism. It can be seeing the three
timings as follows: A- armature starts, B-armature
stops, C-auxiliary contact opens).
In Figure 8 are presented the records of current
through opening coil, operative voltage and travel,
respectively velocity of mobile contact for values
adjusted of the air gap armature of opening solenoid of
3 mm, 7 mm, 9 mm and 12 mm. The reference value is
considered of 9 mm.
Uop
X (mm)
v ·0.06(m/s)
X
Uop·0.83(V)
Ib·0.005(A)
v
Ib
δ=12 mm
δ=9 mm
δ=7 mm
δ=3 mm
Fig. 8. Evolution of opening travel (X), respectively velocity (v) of
mobile contact, operative voltage (Uop), current through solenoid coil
(Ib) at different values of solenoid air gap
In Table 5 are presented the parameter values that
are influenced by the changes of free travel of air gap of
opening solenoid.
- mean operative voltage values decreases with
higher free travel of air gap, respectively increases with
lower free travel of air gap.
6.2. Fault in sensors/transducers
During the experiments, due to many manoeuvres
and high vibration produced on them duration, it was
observed a fault to the displacement transducer.
In case of such anomalies, after analysis the
monitored parameters it can conclude following, Table
6 and Figure 9:
- important changes are observed between the
abnormal travel evolution of the mobile contact and the
record considered normal;
- a significant decrease of maximum velocity is
noticed which is less than 60% from than reference
value, being on below of the limit specified by the
equipment manufacturer;
- the other values of the monitored parameters
were found in specified ranges by the manufacturer.
Table 6. Monitored parameters of circuit breaker on displacement
transducer faults
Current
Profile area
Mean
Travel, Velocity,
through
of solenoid
No. operative
solenoid coil, coil current,
X
v
voltage,
U
opm
crt.
Ib
PA
(V) (%) (mm) (m/s) (%) (A)
(%) (A·s) (%)
1
216.4
100
214
5.58 100
0.76
100
0.62
100
2
216.6
100
214
3.24
0.76
100
0.60
97.8
58
Table 5. Monitored parameters of circuit breaker at different values of solenoid air gap
Free travel of
Mean
Profile area of
Travel, Velocity, Current through
operative
solenoid coil
No. solenoid air gap,
X
v
solenoid coil, Ib
δ
voltage, Uopm
current, PA
crt.
(mm)
(%)
(V)
(%)
(mm) (m/s) (%)
(A)
(%)
(A·s)
(%)
1
9
100 216.7 100
216.8 5.23 100 0.77
100
0.579
100
2
12
133.3 215.7 99.45 216.2 5.39 103 0.77
100
0.7058 121.9
3
7
77.7 218.4 100.69
212 5.79 110 0.75
97.2
0.5329
92
4
3
42.8
221 101.9
218 4.98 95.2 0.77
100
0.463
80
Experimental results obtained provides following
information:
- delays in the appearance of specified timing for
12 mm air gap, which leads to a movement to the right
of the travel of mobile contact, respectively its velocity;
- for the lower values than the reference value of
air gap is observed that specified timings occur more
quickly, resulting in a movement to the left of the travel
of mobile contact, respectively their velocity;
- profile area of coil current increase with higher
free travel of solenoid, respectively decreases with
lower free travel;
- maximum values of the current through solenoid
coil in the analyzed cases have close values;
- maximum values of velocity and travel of mobile
contact are in the specified range by the manufacturer;
Uop
v ·0.06(m/s)
X
Uop·0.83(V)
Ib·0.005(A)
X (mm)
v
Ib
normal
abnormal
due
transducer
Fig. 9. Evolution of opening travel (X), respectively velocity (v) of
mobile contact, operative voltage (Uop), current through solenoid coil
(Ib) with faults on displacement transducer
250
7.
ACTA ELECTROTEHNICA
CONCLUSIONS
The paper presents an online monitoring and
diagnosis system for circuit breakers which have the
role to acquire, to transfer and to process information
about the monitored equipment. The main objective of
such systems is to detect any change in the monitored
parameters based on differences between values and
curves of those parameters.
The monitoring an diagnostic system, on duration
of a trip or closing operation of circuit breaker, allows
to acquisition of analog measurements (main currents
on each phase; currents through the trip and closing
coils; the displacement of mobile contact; operating
voltage), respectively event information (opened/closed
position of circuit breaker; sulfur hexafluoride (SF6)
pressure; motor starting of operating mechanism; the
behaviour of motor protection), quantities necessary to
establish the technical state of monitored equipment.
It was developed a LabVIEW software application
used for processing and analyzing the data acquired by
the monitoring system which enable advanced data
processing and visualization of the monitored
parameter waveforms, both for normal, respective
abnormal condition for an easy interpretation of data.
Calculation of monitored parameters and display
the waveforms was performed after wavelets-based
adaptive filtering of the acquired signals, filters that are
used to perform denoising and detrending of the
original signal.
After the analysis of acquired parameters, in the
case of fault in solenoids, respective faults in
transducers, it can conclude following:
- at a fault in solenoid is observed that all
monitored parameters are changed by the reference
record.
- on displacement transducer fault is observed a
significant difference on travel evolution of mobile
contact, respectively of its velocity values from the
reference.
The obtained results can be used to analyze
other circuit breakers with similar characteristics.
Acknowledgment. This paper was realised with
the
support
of
POSDRU
CUANTUMDOC
“DOCTORAL
STUDIES
FOR
EUROPEAN
PERFORMANCES
IN
RESEARCH
AND
INOVATION” ID79407 project funded by the
European Social Found and Romanian Government.
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1.
PhD. student Mihai ANDRUŞCĂ
Prof. dr. eng. Maricel ADAM
PhD. student Răzvan PANTELIMON
Prof. dr. eng. Adrian BARABOI
Lecturer dr. eng. Cătălin PANCU
Faculty of Electrical Engineering,
“Gheorghe Asachi” Technical University of Iasi
Bd. D. Mangeron, nr. 21- 23, 700050 Iaşi,
ROMÂNIA