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CIRED2005
Session No 1
Summary - This work describes the experience obtained in
the Circuit Breaker System Monitoring project executed for
two Brazilian electric utilities, one of transmission and
another of distribution. The project had as main
characteristic the use of market available equipment and
standardized communication protocols, inside of an open and
flexible architecture, that allows its application to circuit
breakers with different technologies and with different
operating mechanisms and insulation systems.
Keywords: Circuit Breaker System Monitoring, Maintenance
and Diagnostic Equipments. Data acquisition systems.
I. NOMENCLATURE
CB Circuit Breaker.
CMS Condition Monitoring System.
IED Intelligent Electronic Devices.
IHM Interface Human Machine.
SCADA Supervisory Control And Date Acquisition.
II. I NTRODUCTION
he circuit breaker maintenance in electric power
substations has been traditionally based in time (fixed
intervals). That criterion, besides having significant costs
for the utilities, usually isn’t the answer to an immediate
need of maintenance being used since the beginning until
recent times, when the substations possessed permanent
maintenance teams. In that way, the equipment could be
monitored regularly, with the periodic visit of the
maintenance groups to apply the inspection routines:
making a general revision, executing measurements,
recording data and taking samples for analysis. In case a
bad operation or an imminent fault is determined, an
extemporaneous maintenance will be, consequently,
realized.
The Circuit Breaker is one of the most important andcomplex in all the equipment of the substation. He
possesses a current interruption system and is used for the
1 M. S. Silva is a researcher in the Generation, Transmission and
Distribution Automation Group (GAGTD – EPUSP) at the University of
Sao Paulo, BRAZIL. milthon.silva@poli.usp.br
J. A. Jardini is Professor in the Department of Electrical Engineering
(PEA) at the University of Sao Paulo (EPUSP), BRASIL.
L. C. Magrini is a consultant and adviser of the Generation,
Transmission and Distribution Automation Group (GAGTD – EPUSP) at
the University of Sao Paulo, BRAZIL.
maneuvering and protection of circuits; this is due to its
high isolation interruption capacity of overload currents
above the nominal value as well as of short circuit currents.
In agreement with previous researches, it can be affirmed
that more than 40% of the maintenance cost of the
substation equipment are spent in Circuit Breakers, and
60% of that amount is destined for general revision [6] and
[11]. In this way, the predictive maintenance systems based
on the continuous monitoring of Circuit Breaker
parameters can provide significant reductions in those
costs.
The challenge of the predictive maintenance systems(monitoring) for Circuit Breakers is the possibility of
working with in-service equipment from different
manufacturers that used different operating mechanism and
interruption technologies. In contrast, for example, with
power transformers, whose operational beginnings and
monitoring demands are essentially the same,
independently of the manufacturer.
While projecting a Circuit Breaker monitoring system, it
should be made acquisition of relative variables data: the
internal isolation (for example: pressure of gas SF6); the
operating mechanism (for example: oil pressure in the
hydraulic system); and the command circuits (for example:state of the opening coil contact).
An important measurement is the determination of the
times involved in the several operative stages of the Circuit
Breaker (for example: opening command, opening coil
operation, beginning of arc extinction main contact
opening, end of travel main contact opening and current
interruption).
The variables stored information analysis in the database
makers possible to determine the real condition of the
Circuit Breaker operation. Nowadays there exist a great
offer of Circuit Breaker monitoring systems, and this
number is growing quickly, with the emergence of new
measurement, supervision and control devices both for
hardware and software. On the other hand, that hinders his
integration vastly, since very often they are specific for a
determined manufacturer or for a determined Circuit
Breaker model. To this reality, it becomes convenient the
development of a general monitoring standard, based on
the use of acquisition devices largely used in the industrial
automation.
ON-LINE CONDITION MONITORING SYSTEM FOR IN-SERVICE CIRCUIT BREAKER
Milthon S. Silva, José A. Jardini, Luiz C. Magrini.1
PEA. Department of Electrical Energy and Automation Engineering, Polytechnic School of the University of Sao Paulo
Brazil
T
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CIRED2005
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The condition information of the Circuit Breaker
collected by the monitoring system can be compared with
the data obtained by other equipment already existent in the
substation, in this way making possible a better
characterization of the real condition of the Circuit Breaker
components, as well as of their operational parameters and
so allowing to anticipate and prevent damages or futurefaults whose consequences could cause, aside the
interruptions and respective penalties, high costs of repair.
That predictive characteristic also allows a best
programming of the maintenance teams, correct
administration of the stock, aside of better operational
income of the substation and the Circuit Breaker useful life
prolongation.
III. CIRCUIT BREAKER MONITORING
Circuit Breakers together with the transformers
constitute the most important equipment in the substation.
Considering his maneuvering function it can be said that aCircuit Breaker is usually in an inactive state, since it
usually stays open or closed for long periods of time, until
it occurs an alteration of the normal conditions of system
operation, moment in which it should operate to change of
state. However when a Circuit Breaker has to work, a
wrong operation or a fault in the interruption can create a
severe disturbance in the system, for this reason it should
have a well projected operating mechanism and highly
safe.
The Circuit Breaker monitoring system is a real time
supervision system of the Circuit Breaker main parameters
(currents, voltages, pressures, temperatures, contacts, etc.).This supervision is made through digital equipments and
special sensors that are installed in the Circuit Breaker. The
data are collected and processed in a data acquisition and
control unit (UAC), to thereafter through a communication
network, using desirably a protocol standardized
internationally, be sent to a central computer located at the
control building of the substation and later to the operation
centers and so allowing a remote supervision.
In the supervision computer it is installed a database
manager program that stores the information history
collected during the Circuit Breaker operation. A SCADA
program that aside of collecting periodically theinformation provided by the UAC, maker possible the IHM
between the monitoring system and the substation operator.
A dedicated program of supervision that allows to
transform the data of the historical database in information,
continually making calculations and presenting the state of
the Circuit Breaker monitored components, in the form of
waveforms, graphs or charts, in a way to make possible an
evaluation and objective analysis of the Circuit Breaker
real condition, which will guide the programming of its
maintenance. It is the main objective of the system, the
minimization of the equipment amount of faults and the
reduction of the number of programmed maintenances
during the useful life.
For the implementation of these monitoring systems
there were chosen: a Circuit Breaker (D1) that maker part
of a 440 kV transmission substation and other Circuit
Breaker (D2) that is installed in a 69 kV distributionsubstation, whose operating mechanism is detailed:
D1) Circuit Breaker 440kV with monopolar operating
mechanism (independent panel command for each
phase). Each pole possesses two isolated post mounted
on a common base. The head with double operating and
the post is filled out with gas SF6 used as half insulating
and arc extinguisher. The density of the gas is controlled
through a densimeter, being its pressure shown through a
manometer. The head transforms the vertical movement
of the maneuvering rod into a horizontal movement of
the movable parts in the interrupting units. The
maneuvering rod works with an electro hydraulic type
mechanism that moves in the vertical direction. The
energy produced by the nitrogen gas (compressed inside
the hydraulic accumulator) activates the circuit Breaker
operation mechanism. Tubes leaving this drive the
pressurized oil to the respective operation in each polar
post, to the unit of valves and the control cabinet in
which it is made the supervision and control of the
compressor medium (óleo/N2).
D2) Circuit Breaker 69kV with tripolar operating
mechanism (one panel command for the three phases),
that uses the technique of the arc rotative associate to the
self-expansion. The current to be interrupted travels a
concentric coil to the contacts axis. The magnetic field
originated induces the arc to make fast rotations on the
surface of the arc contacts, making possible that the
heating of the contacts are distributed. The elevation of
the operation pressure provokes the gas SF6 blow out on
the arc for its extinction. The operating system is
mechanical, composed by a group of levers, with
accumulation of energy by springs activated through a
DC current motor.
Although those Circuit Breakers work in different
voltage levels and possess different principles of operating
mechanisms, some monitoring parameters are similar.
Thus, the main characteristics of a Circuit Breaker that can be generally measured and monitored are:
Closing and opening coils currents
Line phases currents
Motor operating currents
Voltages supply (AC and DC)
Phases voltages
Operating mechanism
Main contacts travel
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Wear of the contacts switch
Insulation medium pressure
Intern temperatures
Supervision contacts state
IV. MONITORING SYSTEM PARAMETERS
In the acquisition of the variables and states of the
Circuit Breaker it should be considered two basic types of
hardware interface:
A. Digital Inputs
They are signals that are collected continually especially
in the moment of the Circuit Breaker operation. Depending
on the nature of the signal, these can be colleted with fast
resolution (High Sampling - HS) or slow (Low Sampling -
LS). HS is used when we will make the recording events,
for determination of the operation times and for thecomparison with obtained values of other substation
monitoring equipment. The signals LS are usually used as
alarms, such as information of the state of the pressure
levels and levels of voltages supply DC and AC, and their
resolution is in the order of seconds. In Table I, the Circuit
Breaker digital inputs, are shown.
TABLE I
MONITORED DIGITAL I NPUTS
B. Analogical Inputs
The monitoring of the electric variables comes with two
needs: one with low resolution of time (Low Sampling -
LS), being necessary and enough to collect in minutes
intervals, usually used for operation condition variables;
and the other with high resolution (High Sampling - HS)
collected during the Circuit Breaker operation.
Those events are fast so that with a high sampling rate,
it’s possible to make a correct oscillography of the variable
and in that way to observe any type alterations inside of the
normal pattern of operation. Table II, shows the different
Circuit Breaker analogical inputs.
TABLE II
MONITORED A NALOGICAL I NPUTS
The amount of analogical inputs will depend on the type
of the Circuit Breaker (monopolar or tripolar), of the
comparison need among the values of each phase and of
the operating mechanism type, among others.
In this monitoring system, the signals of the current and
voltage phases are obtained through the PTs and CTs
command panels of the line, with 5A and 115V outputs
respectively.
For the motor and coils (opening / closing) current
monitoring, closed loop (compensated) current transducers
CB1 CB2 Signal Sampling
Tags Rate
Y Y ABreaker normally closed
contact (NC)HS
Y Y BBreaker normally open contact
(NO)HS
Y Y CB Operating locking LS
Y N Oil-1Low oil pressure, 1st stage
(Alarm)LS
Y N Oil-2Low oil pressure, 2nd stage
(Trip)LS
Y Y SF6-1Low SF6 pressure, 1st stage
(Alarm)LS
Y Y SF6-2
Low SF6 pressure, 2nd stage
(Trip) LS
N N M-1 Operating motor contact (on) HS
Y Y Vol-1 Lack of voltage relay (Vcc) LS
Y N Vol-2 Lack of voltage relay (Vca) LS
Y Y M-2 Spring charging motor (off) HS
Y N D-P Phases discordance HS
Y N R Auto-reclosing (on/off) LS
DescriptionYes/Not
CB1 CB2 Signal Sampling
Tags Rate
Y Y TA Environment Temperature LS
Y Y TI Inside Cabinet Temperature LS
Y Y D Gas SF6 density LS
Y N P Oil Pressure LS
Y Y C Close coil current HS
Y Y T-1 Open coil current (Trip1) HS
Y N T-2 Open coil current (Trip2) HS
Y Y M Motor Current HS
Y Y P Phase Currents HS
DescriptionYes/Not
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of Hall effect were used, with 100/0.1A relationship of
transformation.
V. MONITORING SYSTEM ARCHITECTURE
The monitoring system is composed by a group of
devices (transducers, converters and sensors) that are
linked to an IED that makes the collection, treatment and
subsequent sending of the data to the central computer
that processes, stores and accomplishes the Interface
Human Machine function (IHM). The IHM converts the
data in useful information to the Circuit Breaker real
condition diagnosis and for the communication are used
standard protocols.
The general architecture of the CB monitoring is show in
the Figure 1.
Figure 1. General architecture of the Circuit Breaker System Monitoring.
A. Acquisition Module
This module is composed by an IED with 240kB of
memory configurable, a power supply of 125Vdc with 24
Vdc output for feeding possible sensors, data transmission
rate from 9600 to 19200 bps, Ethernet communication
card, two EIA RS-232/RS-485 ports. Acquisition Card
(I/O) of binary inputs with 12/24/125Vdc feeding and
analogical inputs of +/-10Vdc or 0...20mA with 16 bitsresolution and accuracy of 0.1%.
The IED is prepared to work in atmospheres with high
noise level originated by the electromagnetic fields and to
support environment temperature appropriate to the
substation historical temperatures.
B. Digital Transducers
They are transformer units for adaptation of the line
currents and voltages (phases A, B and C), with
configurable inputs for one or three phase circuits. The
input for these units are voltage from 0 to 115V and current
from 0 to 5 A, being these connected through CTs and PTs
of line bay. The transducers are connected to IED
monitoring through the acquisition card analogical inputs(0 to 5 Vdc).
C. Sensor specifications
Temperature Sensor. - Model Pt-100 class B / RTD,
this sensor is usually fixed in the own CB panel of
command hold a temperature transducer for 4 to 20mA
output, power supply of 10 to 30 Vdc, connection to
two wire, with protection tube in stainless steel,
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measurement of 0°C to +85°C and accuracy of +/-
0.5%. Another sensor with the same characteristics is
used for measurement of the environment temperature
and will be installed close to one of the poles.
Density Sensor. - Model S-10, with pressure
measurement from 0 to 10 bar with temperaturecompensation, two wires circuit, power supply from
10 to 30 Vdc, output signal from 4 to 20 mA, pressure
connection ½" BSP, accurately of +/-0.5% and time
response smaller than 1s.
Pressure Sensor. - Model S-40, with pressure
measurement from 0 to 400 bar, two wires circuit,
power supply from 10 to 30 Vdc, output signal from 4
to 20 mA, pressure connection ½"BSP, accurately of
+/-0.5% and time response smaller than 1s.
Current Transducers. - Type close loop (compensated)
of Hall effect, with measurement variation from 0 to
10 A (DC or AC), three wires circuit with power
supply from 20 to 30 Vdc, output signal from 4 to
20mA, connectionless physics used for measurement
of the coil and motor currents, accuracy of +/-0.5%
and time response smaller than 1s.
D. Computer Monitoring Server
It consists of a microcomputer, located in the utilities
substation control building, PC of 2 GHz, with 256MB
RAM memory, 40GB HD unit, monitor 17" with card
graphical interface AGP and communication cards with
RS-232 ports. In the computer it was installed the
WINDOWS NT professional operating system, theSCADA system, a database management program, as well
as a program developed for analysis and data presentation
showing the results in form of graphs, tables, waveforms,
among others.
E. Communication
The needs of data communications of the Circuit
Breaker monitoring system, although they don't involve a
great volume of data, it presents some peculiarities, such
as:
Different times of scanning, most of the digital and
analogical signals are collected every second, while
some others demand a resolution of milliseconds.
The volume of data to be transmitted is usually small,
except when it occurs a maneuver of the circuit
breaker.
The equipment collecting the data, need to be
synchronized.
Manufacturers offer a great variety of data
communication protocols with support to those
functionalities, but many of them are solutions supported
just by the market products of the company, which hinders,or even, prevents its integration with other system
equipment or even with SCADA.
The philosophy of open communication systems values
the adoption of interfaces and standardized protocols, such
as IEC 60870-5, DNP 3.0 and more recently, IEC 61850,
which is also known as an extension of UCA 2.0.
F. Other Devices
Regarding the considerable distances between the field
equipment and the control building, there were used fiber
optic cables, with their respective F.O. / RS-232converters. In case of the Circuit Breaker (D1) because it
has a monopolar operation it demanded the triple of the
amount of sensors and one auxiliary power supply of 125 /
24 Vdc.
Figure 2, shows the prototype that was installed in the
transmission substation with all the devices before
mentioned.
Figure 2. Prototype installed in the transmission substation.
VI. OBTAINED DIAGNOSES R ESULTS
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Evolution waveforms of the gas density (SF6), oil
pressure and temperature changing, through data by
the sensors installed in the Circuit Breaker.
Currents and voltages of line oscillographies provided
by the digital transducers, that allowed to make
calculations in an approximate way the main contacts
wear and damage using the relationship I
2
T. Evolution of the closing and opening times, through
the measurements of the operation times, as well as by
the position of the auxiliary contacts.
Analysis of the Circuit Breaker closing or opening
times, through the phase current oscillographies and
opening / closing coil currents.
Analysis of the main contacts travel.
The analysis of the Circuit Breaker closing and
opening current waveforms will permit to detect
possible faults in the Circuit Breaker operation,
determining his characteristic signature.
Evolution of the Circuit Breaker motor operating
current waveforms.
Analysis of the disagreement between main contacts
opening and closing times.
VII. CONCLUSIONS
The Circuit Breaker monitoring in real time is an
emerging technology that it’s growing quickly with the
participation of utilities, equipment manufacturers,
monitoring devices providers and universities research
groups.
The appearance of new acquisition cards with high
sampling rate larger to 1ms allows to accomplish
current oscillographies involved during the Circuit
Breaker operation process, which allows to detect
probable fault in his operation, besides allowing to
accomplish much more exhausting analyses through
the use of mathematical tools as the Wavelet
transform.
The selection of data communication protocols is an
important task in order to get an economic solution,
and provide interchangeability avoiding proprietary
systems.
The standardization of the communication protocols
for the monitoring systems will allow to reach benefits,
such as larger integration between equipments, larger
reliability in the data management, smaller response
time before a fault in the system, among others.
As future tendencies into the electric area monitoring
systems: the compact substations monitoring, the
integration of all monitoring systems of several
equipments (transformer, Circuit Breaker, surge
arrester, among other) inside of a common platform
and the appearance of new services such as tools for
maintenance management.
VIII. ACKNOWLEDGE
The authors wish to thank Luis Antonio Solis and
Antonio Corvo of ETEO – Empresa de Transmissão de
Energia do Oeste Ltda. and Francisco Eugenio Veiga of
COELBA – Companhia de Eletricidade da Bahia, for their
contributions and participation in the project execution.
IX. R EFERENCES
[1] A. Poeltl and M. Haines, "Experiences with condition monitoring of
HV Circuit Breaker," in Proc. 2001 Transmission and Distribution
Conf., IEEE/PES, V.2 pp. 1077-1082.[2] Catalogs Circuit Breaker from Siemens and Schneider.
[3] CEA Canadian Electricity Association, “On-line Condition
Monitoring of Substation Power Equipment Utility Needs, Dec.
1996.
[4] IEEE “Guide for the selection of monitoring for Circuit Breaker”
IEEE Std. C37.10.1-2000.
[5] J. Corbett and A. Higgins and C. Kelleher, "A procedure for
allocating limited resources to Circuit Breaker planned
maintenance," in Session 2002 CIGRE Conference, V: 13, P : 303.
[6] J. H. Nelson, "Electric utility considerations for Circuit Breaker
Monitoring," in Proc. 2001 Transmission and Distribution Conf.,
IEEE/PES, V.2 pp. 1094-1097.
[7] J. P. Dupraz and A. Schiemann, "Design Objectives of new digital
control and monitoring of High Voltage Circuit Breaker," in Proc.
2001 Transmission and Distribution Conf., IEEE/PES, V.2 pp. 1088-
1093.[8] K. Lehman and L. Zehnder and M. Chapman, "A novel arcing
monitoring system for SF6 Circuit Breaker," in Session 2002 CIGRE
Conference V: 13, P: 301.
[9] M. Landry and G. Diagneault and S. Zelingher, "Benefits of On-line
monitoring for High Voltage Circuit Breaker," in Session 2000
CIGRE Conference pp. 358-364.
[10] O. S. Lobosco and H. P. Silva, "Monitoring systems for failure
detection and location in Substations Strategic Apparatus," in Proc.
2002 Latin America Transmission and Distribution Conf.,
IEEE/PES, V.3, pp. 317-322.
[11] W. J. Bergman, "Selecting Circuit Breaker Monitoring," in Proc.
2001 Transmission and Distribution Conf., IEEE/PES, V.2, pp.
1071-1076.
X. BIOGRAPHIC
Milthon Serna Silva, born in Cusco, Peru, 30
august 1972. Graduated in electrical
engineering at UNSAAC University in 1993.
He received the MSc and PhD degrees in
2001 and 2004 at the Polytechnic School of
Sao Paulo University. Worked in construction
of line and substation high voltage systems
projects and Power System Planning. At the
present works at GAGTD (Energy
Distribution and Transmission Generation Automation Group) of PEA (the
Department of Energy Engineering and Electric Automation) of EPUSP
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(The Polytechnic School of Sao Paulo University). Member of Brazilian
work group SC13.23 to CIGRE and Member of IEEE.
José Antonio Jardini, born March 27 1941,
graduated at EPUSP- The Polytechnic School
of Sao Paulo University in 1963. MSc in 1970
and PhD in 1973. Associate Professor in 1991
and titular head in 1999, all of them at PEA
(The Department of Energy engineering and
Electric Automation). Worked at Themag
Engineering Ltd in the area of power systems
studies – lines projects and automation. At the moment he is a professor at
the Department of Energy Engineering and Electric automation where he
teaches “Automation of the Generation” and “Transmission and
Distribution of Electric Energy”. Repreesents Brazil at SC38 of CIGRE,
CIGRE member, Fellow Member of IEEE and Distinguished Lecturer of
IAS/IEEE.
Luiz Carlos Magrini, born in São Paulo,
Brazil, on May 3rd, 1954. He graduated from
Polytechnic School of Sao Paulo in 1977
(Electrical Engineering). From the same
institution he received the MSc and PhD degrees
in 1995 and 1999, respectively. For 17 years he
worked for Themag Engenharia Ltda, a leading
consulting company in Brazil. He is currently a researcher at Polytechnic
School of Sao Paulo University - GAGTD group. Member of Brazilian
work group SC13.23 to CIGRE.