lI&~•t~"""~.--~.'

Technical Advisory Committee(in alphabetical order)

A Rahim, Univ. of Alabama, TuscaloosaA. Chattopadhyay, BE College, DUA. Domijan,Univ of Florida, USAA. Feliachi, West Virginia University, USAA. Ghosh ,lIT, KanpurA.Chakraborty, BE College, DUA.Deb, Calcutta UniversityA.E Zobaa,Cairo Univ, EgyptA.K.Chakrabarty, CEM, KolaghatA.K.Datta, Calcutta UniversityA.K.David, Hong Kong Poly. UniversityA.K.Mukhopadhyay, Calcutta UniversityA.M.Kulkarni, lIT, MumbaiB.C.Pal, Imperial College, UKB.G.Fernandes, .IIT, BorribayBK Bose,UnivofT.ennessee, USAC.A. Castro, DSEE1FEECIUNICAMPC.Chakraborty, nT, KharagpurD. Kastha, IIT,KharagpurD. Kirschen,UMIST,Manchestor,UKD.Das, lIT, KharagpurD.Ghosh, BE College, DUD.N. Vishwakarma,IT,BHUD.P.Kothari, lIT, New DelhiD.Thukaram,IISc,BangaloreG. Gross,UIUC,UrbanaG. Verghese, MIT, USAH. G.Gopal, SDMCET DHARWADH. Rutnick, Univ of ChileH.Hess, University ofUidaho, MoscowH.P.Kincha, IISc.BangaloreI.J.Nagrath, BITS, PilaniI.R. Hanitsch, TU, BerlinJ. Barros, Unv of Can tab ria, SpaneJ. Heydt, Arizona StateUnv,USAJ. Usaola, Unv of Carlos III, MadridJ&.Jardili,EPU,Sa~ Paulo,BrazilJ .Janda,IIT,Delhi -J .K.Das, Director, CEM, Kolaghat

J.K.Sen, CEM, KolaghatK.Bhattacharya, Jadavpur UniversityK.Bhattacharya, Univ.ofWaterloo, CanadaK.K.Ghosh, CEM, KolaghatK.P.Basu, MMU, MalaysiaK.R.Padiyar,IISc,Bangalore1. Chen, Osaka Sangyo University, Japan1. Jenkins,IlSc,BangaloreL.K.Goel, Nanyang Tech.Univ, SingaporeM Abido, KFUP, Dhahran, Saudi ArabM. Manana, Canteli, Univ of CantabriaM. Ropp, South Dakota State Univ, USAM. Shahidehpour, lIT, Illinois, USAN.Chakraborty, Jadavpur UniversityN .Chatterjee, Jadavpur UniversityN.K.Deb, Jadavpur UniversityN .K.Kishore,IIT,KharagpurN.K.Sancheti, Infilica, BangaloreN.Sinha, NIT,SilcharO.H Abdalla, Cairo Unv, EgyptO.Kilic, YyLdyz Tech Univ, TurkeyO.Malic, University of Calgary, CanadaO;P.Malik, Univ. of Calgary, CanadaP.Bodger, Univ. of Canterbury, NZP.Chowdhury, TTU, Cookeville, TN, USAP.K. Kalra,IIT,KanpurP.K.Chattopadhyay, Jadavpur UniversityP.K.Dash, SIT, ~::':iaP.K.Dutta, IIT,KharagpurP.K.Mukhopadhyay, Jadavpur UniversityP.K.Nandi, BE College, DUP.Kundur, Power Tech, CanadaP.Purkait, HIT, HaldiaP.S.Ghosh,Univ of Tenaga, MalaysiaR.Arora,IIT,KanpurR.Chakraborti, Jadavpur UniversityR.Rayudu,Lincoln Unv,Canterbury,NZR. Sarathi,IIT, ChennaiS.A.Khaparde, lIT, MumbaiS.Baneerjee,IIT,Kharagpur

Technical Session 3B

IT Application in Power & Energy Sector

Paper Title of the Paper Authors PageNo. No.

49 ADSP Based System Approach for Enhanced Efficiency in Asim Datta andSubstation SCADA, Automation and Integration S. Semmpta 337

82 Application of Web Services in the Power Industry Siddharth Likhate, S. A. Khaparde 34268 Problems and Scopes of Introducing Remote On-Line ICT Amit Chaudhuri

Based Management in a Power-Plant, Some Observations & 346from a Real-Life Prqject-Experience Abhiiit Auddy

104 Secure Image Transmission of Distributed Wireless LowPowered Embedded Client-Server Systems and An Approach Abhijit Hazra 350

to Software Power Optimization- .

83 IT Based Assessment of Electric Power Quality of A Power S. Chattopadhyay, M. Mitra,System S. Sengupta 355

30 Harnessing the Power of IT for Overall Improvement of V. Ravishankar, A. Bhattacharya,Power Plant Performance N. Ranesh 359

123 Use of Modern AUtomation and IT Tools for Effective M. R Kappali,Energy Management in Distribution System H. G. Gopal 364

Technical Session 3C

Modern PowerSystem Protection, Instrumentation & Control

Paper Title of the Paper Authors PageNo. No.

102 A Study Report on Modification of a Steam Generation Unit S. C. Bera,in Naphtha and Natural Gas based Fertilizer Plant M. S. BhoWIilick 371

54 Implementation of Circuit Breaker Monitoring System Milthon S. Silva, Jose A. Jardini,Luiz C. Magrini 376

55 Adaptive Filter Structure based Power System Relaying for N. P. Subramaniam, . ,Real Time Applications K Bhoopathy Bagan 381

.

26 Electrical Field Calculation Inside a Dielectric using Finite Prithwiraj Das,Difference Method Ratul Dey 386

.

60 An Efficient Algorithm for Determining the Rating of S.Ghos~S.Sengupta,Distribution Transformers .H. O. Bansal 390

50 An Investigation of Unbalanced Magnetic Pull as a Function Dr. K.P. P. Pillai, .of Static Eccentricity in Inductor Type Brushless Alternator Dr: Achuthsankar S. Nair, 394

G. R Bindu126 Investigation of Sensitivity of Low Voltage Equipments to R E. Kushare,A. A. Ghatol,

Voltage sag and Development of Voltage Tolerance Curve S. Kala .. 398. for Such EqUipment .

135 On-line Diagnosis of Electric Power Quality (EPQ) Through S. Nandi andS.Sengupta . 402Automated Analysis of Loss-of -balance in a Power System

I

Implementation of Circuit Breaker

Monitoring System

4bstract- This work describes the experience obtained in;. .=:rcuit Breaker System Monitoring project executed for: 3~azilian electric utilities, one of transmission and another

: :o:ribution. The project had as main characteristic the use: -"-rket available equipment and standardized communication

~': ::cols, inside of an open and flexible architecture, that- :., 5 its application to circuit breakers with different; ~' -'ologies and with different operating mechanisms and'; _]tion systems. This article also describes the proposal of

" -O'W method for the determination of the circuit breaker. - =~2.tiontimes (opening, closing) through the application of-: Xavelets Transform mathematical tool (WT), in the currents:c' : \oltages presents in the circuit breaker.

Index Term.••- Circuit Breaker System Monitoring, Circuit:: ':2.ker Operating Time, Maintenance and Diagnostic::~_pment.

-:-he circuit breaker maintenance in electric power. -:' ,~ations has been traditionally based in time (fixed- :::"',aIs). That criterion, besides having significant costs for-: ._tiIities, usually isn't the answer to an immediate need of

- :..~Jenance being used since the beginning until recent times,- =~,the substations possessed pennanent maintenance teams.

.-. that way. the equipment could be monitored regularly,:-. (he periodic visit ofthe maintenance groups to apply the

-, :-ection routines: making a general revision, executing- :2.surements, recording data and taking samples for analysis.- : 2.sea bad operation or an imminent fault is determined, an

:'. :err:yJraneous maintenance:will be, consequently,realized.

\-1. S. Silva is a researcher in the Generation, Transmission:""': Distribution Automation Group (GAGTD - EPUSP) at the_:';\ ersity of Sao Paulo. BRAZIL. (telephone: 55 11 3091-5768,:-~.1i1:milthon.silva@poli.usp.br).

J. A. Jardini is Professor in the Department of Electrical:::~gineering (PEA) at the University of Sao Paulo (EPUSP),.= "_-\SIL.

~. C. Magrini is a consultant and adviser of the Generation,-:-'.:.~smissionand Distribution Automation Group (GAGTD -::"CSP) at the University ofSao Paulo, BRAZIL.

The Circuit Breaker is one of the most important andcomplex in alI the equipment of the substation. He possessesa current interruption system and is used for the maneuveringand protection of circuits; this is due to its high isolationinterruption capacity of overload currents above the nominalvalue as welI as of short circuit currents. In agreement withprevious researches, it can be affirmed that more than 40% ofthe maintenance cost of the substation equipment are spent inCircuit Breakers. and 60% of that amount is destined forgeneral revision [2] and [7). In this way, the predictivemaintenance systems based on the continuous monitoring ofCircuit Breaker parameters can provide significant reductionsin those costs.

JI. Circuit Breaker MonitoringCircuit Breakers together with the transformers constitute

the most important equipment in the substation. Consideringhis maneuvering function it can be said that a Circuit Breakeris usually in an inactive state, since it usualIy stays open orclosed for long periods oftime, until it occurs an alteration ofthe normal conditions of system operation, moment in which itshould operate to change of state. However when a CircuitBreaker has to work, a wrong operation or a fault in theinterruption can create a severe disturbance in the system, forthis reason it should have a well projected operating mechanismand highly safe.

The Circuit Breaker monitoring system is a real timesupervision system of the Circuit Breaker main parameters(currents, voltages, pressures, temperatures, contacts, etc.). Thissupervision is made through digital equipments and specialsensors that are installed in the Circuit Breaker. The data arecollected and processed in a data acquisition and control unit(UAC), to thereafter through a communication net..".vrk, usingdesirably a protocol stanCl,;:-di::edinternationally, bc~senf to a:central computer located at the control building of thesubstation and later to the operation centers and so allowing aremote supervision.

In the supervision computer it is installed a databasemanager program that stores the information history collectedduring the Circuit Breaker operation. A SCADA program thataside of collecting periodically the information provided bythe UAC, maker possible the IBM between the monitoringsystem and the substation operator. A dedicated program ofsupervision that allows to transform the data of the historicaldatabase in information, continually making calculations andpresenting the state of the Circuit Breaker monitoredcomponents, in the form of waveforms, graphs or charts, in away to make possible an evaluation and objective analysis ofthe Circuit Breaker real condition, which will guide the

programming of its maintenance. It is the main objective of thesystem, the minimization of the equipment amount of faultsand the reduction of the number of programmed maintenancesduring the useful life.

For the implementation of these monitoring systems therewere chosen: a Circuit Breaker (0 I) that maker part of a 440kV transmission substation and other Circuit Breaker (02)that is installed in a 69 kV distribution substation.

Although those Circuit Breakers work in different voltage1evels and possess different principles of operatingmechanisms, some monitoring parameters are similar. Thus,the main characteristics of a Circuit Breaker that can begenerally 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

.:. Wear of the contacts switch

.:. Insulation medium pressure

.:. Intern temperatures

ill Monitoring System Parameters

In the acquisition of the variables and states of the Circuit3reaker it should be considered two basic types of hardware:r.:erface:

.-1. AnalogicallnputsThe monitoring of the electric variables comes with two

::eeds: one with low resolution of time (Low Sampling - LS),::>eingnecessary and enough to collect in minutes intervals,.:.5'J.al~used for operation condition variables; and the other·.•.i:h high resolution (High Sampling - HS) collected during:::e Circuit Breaker op~ration.

Those events are fast so that with a high sampling rate, it's:'Jssible to make a correct oscillography of the variable and in±Cat way to observe any type alterations inside of the normal: mem of operation. Table I, shows the different Circuit3 ~eaker analogical inputs.

B. DigitallnputsThey are signals that are collected continually especially in

:::e moment of the Circuit Breaker operation. Depending on:!'le nature of the signal, these can be collected with fast:-esolution (High Sampling - HS) or slow (Low Sampling - LS).HS is used when we will make the recording events, for:e:ermination of the operation times and for the comparison',l,~:hobtained values of other substation monitoring equipment.

TABLE IMonitored Analogical inputs

CBI CB2 SignalDescription

Sampling

YeslNot Tags Rate

Y Y TA Environment Temperature LS

Y Y TI Inside Cabinet Temperature LS

Y Y D Gis SF6 density LS

Y N P Oil Pressure LS

Y Y C Close coil current HS

Y Y T-I Open coil current (Trip I) HS

Y N T-2 Open coil current (Trip2) HS

Y Y M Motor Current HS

Y Y P Phase Currents HS

TABLE 2Monitored Digital Inputs

CBI CB2 SignalDescription

Sampling

YeslNot Tags Rate

Y Y ABreaker normally closed

HScontact (NC) ---

Y Y BBreaker normally open contact

HS(NO)

Y Y CB Operating locking LS

Y N Oil-ILow oil pressure, 1st stage LS

(Alarm)

y N ,Oil-2Low oil pressure, 2nd stage

LS(Trip)

Y Y SF6-1 Low SF6 pressure, 1st stage LS(Alarm)

'Y Y SF6-2Low SF6 pressure, 2nd stage LS

(Trip)

N N M-I Operating motor contact (on) HS

Y Y Vol-I Lack of voltage relay (Ycc) LS

Y N Vol-2 Lack of voltage relay (Yea) LS

Y Y M-2 Spring charging motor(off) HS

Y N D-P Phases discordance HS

Y N R Auto-reciosing (on/off) LS

s:gnals LS are usually used as alarms, such as-~::Jnof the state of the pressure levels and levels of~=s s:.:pplyDC and AC, and their resolution is in the order

: =: : :-.:$. In Table 2, the Circuit Breaker digital inputs are

-. = ::.:nountof analogical inputs will depend on the type of. " ~_':11: Breaker (monopolar ortripolar), of the comparison, c:: ~:-:-.cngthe values of each phase and of the operating-:: - ':':-.:smtype, among others.

, ::.:$ monitoring system, the signals of the current and. : -:..:.;=Jhases are obtained through the PTs and CTs command: :. =. sn the line, with 5A and I I5V outputs respectively.

=- ::- the motor and coils (opening I closing) current- :' :: :ing, closed loop (compensated) current transducers of

=:'fect were used, with 100/0. I A relationship of:-:C'.S :.: :-:nation.

~lonitoring System Architecture

~:-e monitoring system is composed by a group of devices:-.=...'S :uc:ers, converters and sensors) that are linked to an lED

:'~: :-:-.2.kesthe collection, treatment and subsequent sending: ... - = :a ta to the central computer that processes, stores and~: : : :-:-.p lishes the Interface Human Machine function (lHM).-. = :E\1 converts the data in useful information to the Circuit:.. =::.,:e:real condition diagnosis and for the communication",'= .s ej standard protocols.

'\.. Acquisition Module

~:-.:$module is composed by an lED with 240kB of memory: '::?,urable, a power supply of 125Vdc with 24 Vdc output:. :eeding possible sensors, data transmission rate from 9600: ::'00 bps, Ethernet communication card, two EIA RS-2321~ ~ S5 ports. Acquisition Card (1/0) of binary inputs with:: ~ 125Vdc feeding and analogical inputs of +1- IOVdc or

: ::-:-,Awith 16 bits resolution and accuracy of 0.1 %..Digital Transducers

~ - ,,:,'are transformer units for adaptation ofthe line currer:~".- : '.o]tages (phases A, B and C), with configurable inputs:' : :-leor three phase circuits. The input for these units are: ::.ge from 0 to I I5V and current from 0 to 5 A, being these: - -.ected through CTs and PTs ofline bay. The transducers'= ::,nnected to lED monitoring through the acquisition card-~. :gical inputs (0 to 5 Vdc).

Sensor specifications

Temperature Sensor. - Model Pt-100 class B I RTD, thissensor is usually fixed in the own CB panel of command:-.olda temperature transducer for 4 to 20mA output, powers:Jpply of IO to 30 Vdc, connection to two wire, with

protection tube in stainless steel, measurement ofO°C to+85°C and accuracy of +1-0.5%. Another sensor with thesame characteristics is used for measurement of theenvironment temperature and will be installed close to oneofthe poles.

.:. Density Sensor. - Model S-l 0, with pressure measurementfrom 0 to lObar with temperature compensation, two wirescircuit, power supply from 10 to 30 Vdc, output signalfrom 4 to 20 mA, pressure connection W' BSP, accuratelyof +1-0.5% and time response smaller than Is .

.:. Pressure Sensor. - Model S-40, with pressure measurementfrom 0 to 400 bar, two wires circuit, power supply from 10to 30 Vdc, output signal from 4 to 20 mA, pressureconnection ~"BSP, accurately of +1-0.5% and timeresponse smaller than Is.

.:. Current Transducers. - Type close loop (compensated) ofHall effect, with measurement variation from 0 to lOA(DC or AC), three wires circuit with power supplyfrom 20 to 30 Vdc, output signal from 4 to 20mA,connectionless physics used for measurement of the coiland motor currents, accuracy of +1-0.5% and timeresponse smaller than Is.

D. Computer Monitoring Server

It consists of a microcomputer, located in the utilitiessubstation control building, PC of2 GHz, with 256MB RAMmemory, 40GB HD unit, monitor 17" with card graphicalinterface AGP and communication cards with RS-232 ports.In the computer it was installed the WINDOWS NTprofessional operating system, the SCADA system, a databasemanagement program, as well as a program developed foranalysis and data presentation showing the results in form ofgraphs, tables, waveforms, among others .

E. Communication

ThB needs of data communications of the Circuit Breakermonitoring system, although they don't involve a great volumeof data, it presents some peculiarities, such as:.:. Different times of scanning, most of the digital and

analogical signals are collected every second, while someothers 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

ON> 3.0 Prdocdcr

CbrM!rtEf" t.b:bE RTU Prdocd Cbm.ErtEl"

RSZ321 Fa Q::tica FbEl"Clltie FO/RS4S5

---~::::::=::::::::::

ItIh Sarmirg1tB9J reus

- t-ileirpJlSofTrip1.Trip2 <n:I cb9i! cdlscurert tJr each pde

• Three irp.ts tJrQ:er.!hg mttorCUTert

ea:hpcle• SDdlllUS br D.rnnts••.•d \Ot'lgES phases

(crsaldVl"S)

I.Dw §ardirgAla9J 1!WlS•Two irpJIS U

T~re9i!nsa-[R-100 a- 420 ~

. 1tree irpJ:s of SF6densitySEl"lSl:.f'

[420~-Three irpJIS of 01 IN2pre$U"l! sensa-

[420~

PowerS4=Po/

125\.60

HID S;;nplrg[ld!3 [pus

• Six irpJ:s tJr Alriliaryool't2l:t (NO <n:I t£)

pdesA Bald C- Sil: illlUS br Ladl ardoperaron rraa- ccnta:t

- One irpJt tJr poledsoortlance

l..cwSul;lbglld!3hp.ts

- TIOO irpJ:s tJr Pres:sue:slates alarm oortaet (01)• TIOO irpJ:s tJr Pres:sue:slates a arm ool't2l:t (SF6)- FoU"hp.tsto OCard PC

\dtage rElayconl3:ts• TIOO hp.ts fa- Gener3

tioc:khg ald 3Jto.redasirg

" Determination of the CB Operating Times

-=-:e input signals that will be submitted to ,the time::"-:.::ation algorithm consist of "vectors" that contain the'.::--.:ling points of the line current and voltage oseillographies': - ;:;?::hphase. Fig. 2, illustrates the oscillography of the='_-~tS in phases A, B and C, after a fault in phase C, in the:r-:'.:ously mentioned substation.

E lr'lth the objective of selecting a base Wavelet function~ conditioned to the analysis of the circuit breaker

, times, tests were realized with several families: Suchconsisted of submitting the oscillography of the current

C) shown in Fig. 2 utilizing several base functions.

The functions: Haar, Daubechies (dbN, N = 1,2,..10),Symlets (symM, M = 2,3".8), Coiflets (coifP, P = 1,2,..5),biorthogonal (biorN, N = 1.1,1.3,..6.8), reverse biorthogonal(rbioM, M = 1.1,1.3,..6.8) and discrete approximation ofMayer (dmey), with different leVels (1,2,..10), they form agroup of forty two orthogonal bases submitted.

Cumtnt phae C

·~f\Vil-\A\H~,JtS;jlIJ\A\H

2OO~~FT1dO' ::..-4 •••. • ..-

-200 : : : : :

d,~~.::J-50~~~-

dl~~~500 1700 1SOO 2100 ZlOO 2500 2700

I

IT1

Fig. 3. Phase C current decomposition during the circuitbreaker opening operation using the db4 WT.

fig. 3, shows the decomposition process of the current in: -:..se-C, after the triggering command of the circuit breaker: :=::ing in the last four cycles before its total extinction, the:·:=.\elet db4 was used and can be observed the alterations:=:;:cted and the possible initial (ITI) and final (FTI) instants::' :he circuit breaker opening operation (arrows).

The starting instant of the opening process (ITI) occurs=.:':=;3 to 4 ms of the digital protection relay departure, which; :::;: time that spends the auxiliary relay to close his digital: ::",tact for triggering the circuit breaker. The final instant?T 1) of interruption of the current when passing through

:;:;0 is suitable for the beginning of a larger alteration in the:=composition signal shown in detail 4 (d4).

The presence of frequencies different from 60 Hz in the-= :':nent of the circuit breaker operation confirm the variations: :-=sentin detaill (d I) of db4 Wavelet Transform, indicating:-,;: 'Jeginning ofthe main contacts' physical separation, inside::;: circuit breaker chamber.

For the detection and location of alterations the algorithm~.=.j~'Zesthe input signal taking a fixed window of a certain:..::nber of samples, usually lI8 of cycle with steps of halfc'· c:;:. Such window of measurements is decomposed using,.':?~.;,so that it is made the analysis of the first four details::=.: characterized the presence of some anomaly in the system,=;::-ecially in the detail I (dI).

When the input signal doesn't present any abnormal. ::..:jation for the system, the ratio between the averages:..3surnesvalues close to one. On the other hand, when the:=.:>tpecomposition detail presents variations different from:-e~anent regime, the ratio between the averages assumes. =':'.lesvery different from one. So, the value of 1.2 was taken:..s::je parameter used for the detection of disturbances, which: :-:,.,ided good results.

As illustrated in Table 3 the error in the calculation of the:_-cuit+Jreaker operation time was < 3% that is an acceptable:-='centage. That error was calculated through the use of the:::-~'NT a.'1d the largest obtained error happened in the faulted:.::..se(C).

TABLE 3Operation Times Calculation

Closing time (ms)Phases Commissioning WT Calculated

I Times timeI A 96,210 97,394

B 98,150 98,091C 97,926 98.152

Opening time (ms)Phases Commissioning WT Calculated

Times timeA 66,180 66,015B 65,000 64,192

i C 68,140 69,953

VI. Conclusions

The Circuit Breaker monitoring in real time is an emergingtechnology that it's growing quickly with the participation ofutilities, equipment manufacturers, monitoring devicesproviders and universities research groups.

The appearance of new acquisition cards with highsampling rate larger to Ims allows to accomplish currentoscillographies involved during the Circuit Breaker operationprocess, which allows to detect probable fault in his operation,besides allowing to accomplish much more exhaustinganalyses through the use of mathematical tools as the Wavelettransform.

Another application could be the determination of thewear-out or damage of the main contacts through thecomparison between the first detail signatures of the signalcollected with the first detail of the reference signal to thenormal operation (new circuit breaker). Thus, differencesamong these waveforms will indicate the presence ofalterations (wear or damage). These signals being able to becompared evaluating the ratio between the average of the firstdetail of the input signal data window and the reference signal,enabling the estimation of different wear-out degrees.

VII. References[I] A. Poeltl and M. Haines, "Experiences with condition monitor-

ing of HV Circuit Breaker," in Proc. 2001 Transmission andDistribution Coni, 1EEElPES, V,2 pp. 1077-1082.

[2] IEEE "Guide for the selectionof monitoringfor Circuit Breaker"IEEE Std. C37.1O.1-2000.

[3] J. Corbett and A. Higgins and C. Kelleher, "A procedure forallocating limited resources to Circuit Breaker pianned mainte-nance," in Session 2002 CIGRE Conference, V: 13, P: 303 .

[4] 1.H. Nelson, "Electric utility considerations for Circuit BreakerMonitoring," in Proc. 2001 Transmission and DistributionConl,IEEElPES, V,2 pp. 1094-1097.

[5] J. P.Dupraz and A. Schiemann, "DesignObjectives of new digi-tal control and monitoring of High VoltageCircuit Breaker," in. Proc. 2001 Trans.'?::ssion ar.d Distribution Coni., IEEElPES,V.2 pp. 1088-1093.

[6] M. Landry and G. Diagneault and S. Zelingher, "Benefits ofOn-line monitoring for High VoltageCircuit Breaker," in Ses-sion 2000 CIGRE Conference pp. 358-364.

[7] W.1.Bergman, "SelectingCircuitBreakerMonitoring," inProc.2001 Transmission and Distribution Coni, IEEElPES, v'2, pp.1071-1076.