CB Monitoring Paper

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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. [email protected]

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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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.

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