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Distortion and System Apparent Power inMacedonian Pow er Distribution System

Jordan S h i k o s k i ,Member IEEE l ad imir Kat ic , Member IEEE

L j u b o m i r N i k o l o s k i,Member IEEE a n d U s t i ja n a Rechkoska. Member IEEE

Abstrna- This paper present the calculationof the distortionpower based on the apparent power definition and evaluatedunder nonsinusoidal conditions. According national andinternational standards [1][8] he nonsinusoidal voltage andcurren t has been m easurement at different location in three-phasePower Distribution System in Macedonia, Based on themeasurement results, related po werquality indexes the distortionpower has been calculated and evaluated its level.At the end ofthe paper are made conclusionsfor the topics discuss.

Index Terms- Harmonics, Distortion, and Power Definitions.

1. INTRODUCTIONHE implication of non sinusoidal waveforms on the

electric power quality. Traditionally analytical definitionsof electric quantities like power needto he re evaluated sincethey have not been defined for nonsinusoidal situations.

Definitions of electric power quantities: active power,reactive power, apparent power, non-active power, distortionpower, etc., under nonsinusoidal conditions has been discussed[1-7]. The main concems are to have an accurate system tomeasure nonsinusoidal current and voltage and to determinepower quality indexes that account for harmonic componentsof the measured power. W e must understand that you can haveharmonics and still have good PQ. While the presence ofharmonics in the power systems of the contemporary

commercial workplace cannot be denied, harmonics cause farfewer PQ problems than they are often blamed for. Theproliferation of adjustable-speed drives (ASDs) and thepresence of other non-linear electrical loads in distributionsystems can cause significant degradation ofPQ. Theygenerate harmonics and subharmonics of the 50Hz or 60Hzpower frequency. These unwanted frequencies distort thepower waveforms and can interfere with the operationofsensitive electronic equipment, both in other parts of the plantgenetating the harmonics and in the distribution system.

In this paper the based on the power quality indexes thedistortion power in a distribution system in Macedonia isdetermined.

T .elivery of power is one of the most important topics of

J Shikaski is with A. D E M 0 - O h i d , P.0.Box 118, 6000 Ohrid.

V. Katic is with Faculty of Technical Sicncc, Universi ty of Navi Sad,

Lj. Nikoloski, i s with, Sv. Kitil Mstodij University. 1000 Skopje.

U.Rschkaska is with Electric Power Company of Macedonia. Ma kd .

Macedonia e-mail: jordanr@mt.net.mk).

Jugoslavija, 210 00 Novi Sad e-mail: katav@uns.ns.ac.yu).

Macedonia. (e-mail: nl jubc@ecren i . e t f .uk im.ed~ ,~k)

Prow. 17,600 0 Oh id. Macedani (s-mail: ustijana@amak.cam.mk)

This paper is organized as follows, first the analyticalformulation calculating method is described, after that the fieldmeasurement is explained. then, measurement and calculatedresults are discus, and finally, the main conclusionsof thepaper are described.

11. POWER D E F I N T ~ O K SNDER NONSINUSOIDALCONDITIONS

When the present work deal with the power (energy),i t isconvenient to revien some of the definitionsof powerquantities under nonsinusiodal conditions proposed by the[EEE Working Group on Nonsinusoidal Situations[I].Existing power definitions for three-phase systems work wellwhen voltage and current are sinusoidal. However, undernonsinusoidal conditions. new definitions of power have beenproposed. For a three-phase case, the instantaneous voltageand current expressions under nonsinusoidal conditions aredefined as:

i ( t )= I , ,+&xI , s in (hwt+p , ) 1)

v t ) = V, + x Y h i n ( h w t + a h )

h=l-(2)

h=l

where:V, ~ In DC voltape and c m l ompancnls

V, I = mas value o f he h volra e nd cum111 armonica h . , =Phase angle ofthe h?wItage and current harmonico = 2n f = anpl ar speed ai fundamental frequency f

The general expressions for the r m s current and voltage,separaring the fund amental and harmonic componen ts, are:

k J ; F = J m (3)

where:Vi. : =rumof therquaredmrvaiucsof valtage,andcurrem harmonics

The rms. current and voltage may b e calculated:

where:V, , V,, \:, = line to mumi s oltages. phase a. b, and c respecliwlyI , , I I / = rmrcur ren l r.ph~iea . . a n d c . respectiwly

0-7803-7671410211617.000 2 W 2 IEEE 455

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The fundamental components of therms current and voltagemay be calculated:

The exp ressions for displacement power factor (DPF), andtrue power factor (TP F) are defined as:

City Type of load

S YAnd the total non-fundamentalrms components

12 - C ~ h + ~ h ~ h

It should be mentioned that various definitions relative tononsinusoidal conditions have been under debate since manyyears ago, and it seems that new definitions will continueappearing. Thereis for instance, another po wer factor definedas the harmonically adjusted power factor (HAPF), in whichthe current of the apparent power is corrected by a weightingfactor related to theskin factor in conductors.

=Cv i + v i+vi( 6 )

3- h t l 3 h t l

Th e system apparent powerS s defined as:

S = 3VI (7)

Location

or, in terms of the fundamental and harmonic componen tsas:

S = S j + S 6 8)

. ..power SI,), and can be divided a s follows:

S ~ = ( V, I , ) = P, ? + Q ~

si = ( v I l H y( v H I , ) z ( V H I H ywhere:P = v, I COS e , = fundamenlal active powerQ ) v, I sin e, = fundamental reactive power8 , = a , = fundamental hase angle

Ohrid Welding equipment I A.D. E M 0Gostivar Electric eauinment I Substation Go stivar

In the squared distortion powerSD, the term Vll , l , calledthe current distortion power,is usually the dom inant term, andexists even in the case when the voltageis perfectly sinusoidalif >O. The second term V ~, lj, alled the voltage distortionpower, is a reflection of the v oltage distortion at the observedbus. The third term V,J, is called the harmonic amarent

11)

111. HARMONIC DISTORTION N THE MACEDONIANDISTRIBUTION NETWORK (FIELD MEASUREMENTS)

The objectivein the present work was to perform a seriesofPQ m easurements at m etering points of different consumers todetermine the levels of gene rated distortion and to evaluate thedistortion power. This pape r presents the results of harmonic

distortion surveys performed atsix different locations, in theMacedonian distribution network. The sites were selected.based on the suspicion that these sites could be generating highamount of distortion. The characteristics of the six industriallocations are listed below.

TABLE

Prilep Elec t r ic motors Tobacco Factory

Skopje Electric fumace Steel Factory

Skpoje I Electronic equipment AerodromeBitola Electric eauimn ent I Substation Bitola

= (EV,I, cos6, + ih d

where:P,, = total harmonic active powerQ, total harmonic nonactivepower

0 , = a P = harmonic phaseangle

The NRM 111 (German measurement system) wasdesigned to evaluate different parameters from the voltage andcurrent waveforms. The current circuits of the measurementsystem NRM I l l are connected in serial with watt-hour meterinput current, but the current transformers connections has10

the measurement instrument NRM III is inserted in theI , , , vi12 V . J i i 2 circuit. The measuremenls were c arried out within a periodof

5 to 8 days. The parameters evaluated were: voltage andcurrent rms values: total harmonic distortionin voltage andcurrent (THDV and THDI); and detection of the three mostsignificant harmonics in voltage and current. Thiswhere:

THDV= total harmonic distonion involtage measurement system is based on the notebook computer withM D I = total harmonic distortionin eumnt program for measurement control, measurement results

=(-) t -) + L)(12)V J ,1

= THDI) THDV) THDI.THDV)

THDV.THDI = normalized harmonic apparent power processing, statistic processing of the results and review, aswell as circuits for entering and processingof measurement

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Phase A PhaseB Phase C

MINIMUM,AXIMUM.VERAGE VOLTAGE VALUES.

Phase A PhaseB PhaseC

A.D.EM0

Gosiivir

TobaccoFac

Steel Fac

4.90 51.86 16.35 5.30 53.32 16.71 4.37 51.64 16.10

0.00 203.6 144,3 0.00 198.3 137.9 0.00 201.3 142 s

23.10 110.7 59.96 21.68 108.5 57,55 22.46 113.7 60,40

49.04 294,s 159.4 47.60 296,6 162.5 50.32308.5 178.6

The THDI valuesin general exceeded the5 . as expected.From Table 5 , it can be seen that in some locations(Aerodrome, SubstationB, A.D. EMO, Tobacco Factory andStee l Fac tory) the recor ded THDI,,, was high.

Location min

TABLE .

man avp min max avg min m a avg

Table 6 shows that only one location, Aerodrome, hadTHDV,, above 5 . All the other locations presentedacceptable THD V values (less than5 ).

TABLEI.M I N I M U M .M A X M U M AN0 AVBKAGETHDVVALUES

However, the THDI,,, occurred only at som e particularsamples. Therefore, THDI ave rage values represented a morerealistic behavior of the current distonion.

From these average values, it can be observed that onlyGostivar, Bitola and Tabacco Factory presented less than5in THDI.

Using the power definitions according formulas in section11, the distortion power can be fo und.

Steel Factoty

Substation Bilola

Substation Go stivar

Tobacco Factory

Aerodrome

A.D. E M 0

TABLEVll.APPARENT AND D~STORTIONOWER ALCULATEDALUES.

ILacarion S(kVA) SD(kVA) ( S , / S )

31 055.42 176.15 0.6

14 806.33 120.92 0 8

2 470.71 48.61 1 9 i

I 0 4 8 3 I 6 3 0

788.45 28.03 3.6

293,63 17.02 5 . 8

The arithmetic power S can be compared with systemapparent power, S, and compute the percent error accordingthe following equation:

1OO(S, - SE , =

S

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Where SA ca be compute according:

Gostivar

Tobacco Factory

Steel Factory

Th e obtained erro r values are given in the following table:

TABLEVOI.POWERSOMPAREDRROR.

Location S S A EA

2 470.71 2470.25 -0 02

I0 48 1048.15 -00033

31 055.42 31015.64 -0 13

Bitola 14 806,33

Additionally, having in mind that Power System inMacedon ia has to operate in the common European Union andBalkan Electricity Market, the restructuring must improve thepower quality issue.

VI. REFERENCESIEEE Working Gmup in Nonsinusoidal Situations: Practical

Definitions for Powen in Systems with NansinuroidalWaveformmrandUnbalanced Laads: A Discussion . IEEE T ransaction on PowerDelivery. Vol. I I . N o . I . January 1996.pp.79-98.P Filipski. A New Appmaeh to Reactive Current and Reactive PowerMeasurement in Nansinusoidal Systems;' IEEE Trans. onInst.Meas.. Vol. 29, Dec. 1980,pp. 423-426.L. Cm cEk i . What i swrong with the Budeanu Concept of Reactiveand Disionim Power and why it Should be Abandoned, EEE Trans.on nst. &Meas.. Vol. 36, Sept. 1987, pp. 834-37.I . Enslin, 1. Van Wyk. Measurement and Compensation of FictitiousPower Under Nansinusoidal Voltage and Cu mn l Conditianr, IEEETrans. on nst. Meas.. 1988.A. Fcrrem. G . Supeni-Furga. A New Appm rch to the Definitions ofPower Components in Three-phase Systems. IEEE Trans.on InstMeas.. Vol. 40, 19 91. p~. 69.577.R. Arssneau, P.S. FUipski, Application of a Three PhaseNonsinusoidal Calibration System for TestingEnergy and DemandMeters Under Simulated Test Conditianr. IEEE Trans.on PowerDelivery. Vol. P W R D J , No. 2. July 1988.pp. 874-879.A. E. Emanuel.: Apaml Power Definitions for threephase SirtemBEE Transaction on Power Delivery. Vol. 14, No. 3, July 1999.pp.767-772.IEEE Std 519-1992, BEE RecommendedPractice and Requirementsfor Harmonic Control inEl. Power Syjtcm.

VII. BIOGRAPHIES

J o r d a n Shlborkl received his M. Sc. degree in Electrical EnginMngfromArimona Slate University in May 1998.His employment sxperisnce included the Arizona Public Service Company,Phoenix; Public Service Electric Gas Co., Salem. New Jsney: DetroitEdison CO. Newpan, Michigan,as I&C Engineering Consultant, and withArizona State Univmiry BS mearch assistant.Cumntly he is with A. D. E M 0 - Electrical Industry Engineering, Ohrid.Macedonia, BS Assistant b e n 1Ma nag a for Development andlnvesmmt.He is IEEE Member, Memberaf Infemafianal and National CommittiesofCIGRE. Hisarea of intmst is a power quality, and dm gulation .

Vlndlmir -tie, received his Vh. D. degree in Ele e~ ~i calngineering fUn ivm ity ofBclgrade. Jugorlavija in 1991.Cum ntly he is isa Vmfessar at the Faculry of Technical Science, UniversityofNovi Sad. ugoslavijB.PmfRor Katic i s a Senior Member of B E E - Power Engineering Society,BEE -Industr ial Elecm nics Soeiery, IEEE-lndustnal A pplication Society andChairman of the E E E Joint Chapter an Indusv y Applications, IndusmalElectronics and Power Electronics Smieties at Novi Sad.He is observed Member at CIGRE SC36 Pans), Member of htemational andNational Comminiss ofC lGR E and National Commioseof C U E D .His B I C ~ of interested in modeling of p w e r elccfmnics convrr te~ ndstandsrdization inelectrical engineering and power quality.

LJubomir Nikolorld Ph.D.EI.Eng. is rofessor at L c aculry of Eldz ica lEngineering, Sv. Kiril Metodij University, Skopje.Macedonia.Hi is Chairman of the Macedonian E E E Chapter.

U.RecbkorLs, received her B.Sc.EI.Eng. from Sv. K i d Mao dij Universiryof Skopje. Macedonia.Cumntly she is a superviriar ad the GIS (Geographic InformationSyr tm)p m j m i n Electric Vower Company of Macedonia. and in a p m s m ofgraduating in M.Ss. in ComputerScicnrs at Sv. aril Maad ij UniveniryofSkopje, Macedonia.Ha rea of interest i s GIS fuay logic, andneural nehxork.

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