Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009

THE POWER ELECTRIC AUDIT OF AN URBAN TRANSPORT OPERATOR

Ioan FELEA, Mihnea CÂMPAN, Florin DANUniversity of Oradea, Universităţii no.1, Oradea,

ifelea@uoradea.ro

Abstract – The paper is structured infour parts. In the first part wejustify our concern regarding thepower audit. In the second part wedefine the contours and how to workmaking AEE for an operator of urbantransport. Part three contains asummary of the results, and the lastpart presents the conclusions of theanalysis.

Key words – power electric audit,power efficiency, urbantransportation, power optimization

1. INTRODUCTION

Sustainable development is one ofthe dominant themes of globalization.Operation of this concept, in theenergy field is seen, mainly byreducing fossil fuel in two ways:

• By increasing the energyefficiency of processes;

• By increasing the value ofrenewable energy.

Targets and means of action of theEuropean Union are clearly defined andregulated [8.9] aimed, in essence, by2020, reducing energy consumption offossil fuels by 20% and correspondingincrease in the share of renewable.

In Romania, energy efficiency iswell below that of countries with thetechnology. There are still manyprocesses and services that take place

in Romania's energy intensity of [2-3]times higher than similar processes incountries modernized "flag" astechnologically. In the last period tomake legislative and financial efforts[10.11] to align the state of facts ofRomania to the European standards,both in terms of energy efficiency andin terms of more intense use ofrenewable resources.

Audit of power (AP) is one of theways covered [12] to identify ways ofimproving efficiency of processes ofenergy conversion. EEA conducted anoperator of urban transport - SC URBISS.A. Baia-Mare. After specifying theelements that define the contour andsome specific aspects of mathematicalmodeling, there is given theconclusions of the made study withgeneral interest, taking into account,the weight of the power traction ofRomania and the possibilities toincreased the efficiency.

2. CONTOUR AND THE WORKING METHOD

The AP contour of the electric urbantransport Baia Mare, comprising off: • transformer stations and rectifier: Station S1: Trafo type TTUONAN; 2X1500 kVA(passive reserve) 20 / 0.511 kV Rectifier type RSTU 825/1600-231B1 Own service trafo 40kVA, 20 / 0,4 kV Station S2:

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009Trafo type TTUONAN; 2X1600 kVA(passive reserve) 20 / 0.511 kV Rectifier and own services trafo thesame type as in S1. • Supplying Network (injection andcontact): Injection network (RI): 7 segments[150 ÷ 2600] ml long of ACYEY 300mmpcable, length 5180 ml; Network contact (RC): operates at 600Vcc, sections 7, 9200 ml (aboutdouble), conductor type TTb 80 • The trolley buses fleet, consistcurrently of 3 types of trolley buses:

SAURER GT 560/640-25 - (7 pcs), 148seats, driving asynchronous motor fedby inverter

ROCAR EDM 212 E - (3 pcs), 92 seats,driven by DC motor (classic)

ROCAR EDM 217 E - (1 pc), 156 seats,driven by DC motor (classic)

AP was done in accordance with [12].Based on measurements and

characteristics of equipment andfacilities in contour, the real powerbalance (PB) has been operated, andidentifying measures to reduce energylosses, has been developed optimizedPB.

The documentation also includesevaluation of energy efficiency ofenergy consumption processes, thecalculation of economic efficiency forthe main measures for optimizationassessment elements and environmentalimpact.

The extent of the service performedis played by specific indicators:tours number (CN), distance (D),passenger transported (NCL). InOctober 2008 the value of theseindicators was:

Nc = 2552; D = 38.280 km; NCL = 502.030 passengers;

The average of the indicators listedfor a day are:

Nc = 82 tours/day;d = 1234.84 km/day;ncl = 16.195 passengers/day;

The reference unit associated PB is

one classic work day (24 hours),average. Electricity consumption foran average day was determined from therecords kept in the

• [22.11.2008, at 15:30 ÷29.11.2008, at 15:30] station S1- • [22.11.2008, at 17:00 ÷29.11.2008, at 17:00] station S2- The loading of equipment and plant

during the development of themeasurements were normal for theservice provided by SC URBIS SA BaiaMare. After the development of the BEEfor an average day we will refer tothe annual BEE, based on monthlyrecords of EE.

Devices used so far: • network analyzer (NA) type C.A.8334 B (2pics.), located in thesecondary of the two transformers; • The keyboard devices indicators ofstations S1 and S2; → magnetoelectric voltmeter: [750-0-750] V; → magnetoelectric ampermeter[1300A/75 mA]

• meters for active and reactivepower: Type ENERLUX TCDM-AEMTimisoara, accuracy class 0.5,located in the primary of thetransformers. For example, is presented in fig.1

load curves (P, Q, S) of the S1station, during recording, and inFig.2 load curves (P, S) of thestation S2, for a day of transition.

Fig. 1 - The load curve for analyzedinterval

(station S1)

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009

Fig. 2 - Load curve for the analysisperiod

(station S2)

The values of THD indicators are: • For S1station: THDU = 2402%% THDI = 23038; • For S2 station: THDU = 1554%% THDI = 21711;

For the above evoked level ofdeforming residue it’s justified theevaluation of power losses / energy inthe two winding of the powertransformers. Through aggregation andmediation during the analysis ofrecorded values for the recordedtechnical measures, were obtained thevalues characteristic of the averageday, used to assess energy losses. Inaccordance with the requests of thebeneficiary, the BEE has been carriedout on the following subcontour:

SC1 - Transformation Station –rectifier and supply network, forwhich we have used the followingequation of PB:

Wa = WU + ΔWT +ΔWR + ΔWL + WA (1)

where, Wa - input power, measured at the inlet(separation) of the station with SEN(determined from records of thebeneficiary); WU- useful energy (leaving subcontour),conveyed to the allocated trolleybuses; ΔWT - energy losses on transformers inthe rectifying station based onmeasurements of the technicalconfiguration and operation of thestation in question;

ΔWR - energy losses on the rectifiersfrom the rectifying station, based onmeasurements of the technicalconfiguration and operation of thestation; ΔWL - energy losses on the supplycalculated on the basis ofmeasurements and features sections(TI, TC), have two components: → ΔWLI energy-losses on the injectionnetwork; → ΔWTC energy-losses on the contactsnetwork; → WA- the auxiliary input power instation (the station's own services)

Value size ΔWT, ΔWR, ΔWL isdetermined by calculation based onrecords kept. The value of theauxiliary consumption (WA) iscalculated as follows:

WA = Wa-WaJT-ΔWT (2)

WaJT- input power / recorded on lowvoltage (recordings made by AR);

Evaluations are made for averageday. Energy use is determined bycalculating the relationship (1). Wecalculate the additional losses inpower transformers due to deformingoperation mode [16].

SC2 - trolleybuses, which for was usedthe following equation BEE

Wa = WU+ΔWM+ΔWmec+ΔWA (3)

where, Wa - input power is calculated based onthe results of previous sub contour; ΔWM - energy losses in engines of thetrolley bus, based on the efficiencyand degree of loading (simple model); ΔWmec - energy losses calculated fromthe records in no-loads (at the startin the parking stations); ΔWA-expected energy losses in otherparts of the trolley bus, based onrecords in the task and no-loads basedon its technical characteristics;

Based on equation (3) calculating

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009energy use (WU), representing theconsumed energy for passengerstransport. It will be compared theobtained values with the values fromtechnical card of the trolley bus.Will be make comparisons between the 3types of trolley buses.

3. RESULTS

In fig.3 and 4 are presented chartsof real BEE for SC1 (S1, S2)

Fig. 3 - BEE real SC1 (S1)

Fig. 4 - BEE real SC1 (S2)

To determine the power function ofthe trolley bus in no-loads (P0) wasstarted in conjunction with chartrecords of the two AR [7]. Wereobtained the power components listedin Table 1.

Table 1 - The power components of thePB for trolleybuses

Tip/ S-GT ROCAR ROCAR

Comp Power[kW]

560 212 E 217 E

Pa 64,94 42,6 49,85Po 25,33 16,73 22,71ΔPM 5,84 7,67 10,97ΔPA 3,71 1,51 2,25ΔPmec 15,78 7,55 9,48ΔPu 39,61 25,87 27,15η[%] 61 60,7 54,5

Real PB of 11 trolley buses (SC2),with reference to average day recordsappropriate on average records formany months are given in Table 2.

Table 2 - BEE real for SC2Feature size [kWh] [%]Input power [Wa] 2556,1

05100

Output power 2556,105

100

1. Useful Energy [WU]

1545,305

60,46

2. Losses 1010,8 39,54

• engines [ΔWM] 302,43 11,83

• other electrical

components [ΔWA]

132,31 5,18

• mechanical transmission mechanisms in [ΔWmec]

576,06 22,53

For fixed contour of real BEE weobtain by adding components and havingin mind that energy useful for the twounder contour of the two substations(S1, S2) is the energy absorbed by the11 trolley buses. The results areshown in Figure 5.

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009

Fig. 5 - Sankey Diagram of real PB for the analyzed contour

Indicators of energy efficiency thatis suitable to be calculated [12]: • specific energy consumption for theunit → consumption of power for a tour:

Cc=Wa/Nc=127090/2552=49,8 kWh/tour (4)

→ EE specific consumption per unit oflength traveled

CD = Wa / D = 127090/38030 = 3.7 kWh /km (5)

→ specific consumption of EE perpassenger transported

CCL=Wa/NCL=127090/502030=0.25kWh/passenger (6)

Allowing an average weight for apassenger (75 kg) is finding thatloading to maximum can be calculatedon the specific "t km":

CCD = 127090 / (38280km 25t) = 0,1328kWh / (t km)

Considering the price of a journey(1,3 lei) and the cost EE (0,315 lei /kWh) it can be calculated:

• Value of EE cost for unit "km t”'

Ven/z = (127090 0,315)/(3828025)=0,042 lei/t km

• Income on "kWh" consumed

Ven = (1,3 502,030)/127090=5,14euro/kWh.

Point out that the evaluation ofenergy efficiency indicators has beenbased on data from October 2008.

Environmental impact is evaluated bydetermining the quantity of pollutantsdischarged into the atmosphere [12]:

E = B ∙ Qi∙ ε (7)

B-Amount of fuel consumed in theanalysis (one day) [kg]; Qi-calorific power of the fuel [kJ /kg]; ε - emission factor

We will assess the impact ofadmitting that the energy consumed inS.C. URBIS Baia Mare is produced fromthe lignite having calorific value:

Qi = 1700 kJ / kg = 0.47 kWh / kg

The results are shown in Table 3:

Table 3 - Quantities of pollutantsexpected to be emanated (on average

day, multi- yearly)Pollutants[kg]

The energy componentCons.

ener

Loss ofener. cons.in recovstationsand feednetworks

Lossof

ener.inthetrans.

SO2 153,6

53,5 39,57

NOx 2,84 0,99 0,73CO2 1390

,8484,7 358,3

4. CONCLUSIONS. OPTIMUM BALANCE

Measurements and assessments made inthe audit (AP) of the contour

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009established by S.C. URBIS Baia Mare -the electric urban transport,composed of transformers – rectifierstations (S1, S2), the supply(injection and contact) and trolleybuspark - allow formulating the followingconclusions: 4.1. The energy efficiency of equipmentand contour of the structure it fallswithin the normal limits for suchsystems. 4.2. Power transformers and rectifyingstations (S1, S2) is well below therated output. Thus the apparentmaximum load recorded during intervalin which the records with the networkanalyzer is 326.2 kVA - for station S1, with thepower transformer rated 1500 kVA; 220.7 kVA - for station S2, with nominalpower 1600 kVA The average value of relative loading(β) is well below optimal relativeloading (β0) of power transformers, asfollows: For trafo of station S1: βm = 0.081and β0 = 0.64, so S0 = 960 kVA For trafo of station S2: βm = 0.041and β0 = 0.54, so S0 = 864 kVA For rectifiers this under load regimeof this arrangement is beneficial bothin terms of energy efficiency as wellas in terms of reliability. For transformers, the under load regimeimplies energetic inefficiency underthe energy issue, which is reflected inchart of balance of powers, on thecontours of analysis, energy losses intransformers is 6.16% of energy came incontour. 4.3. The two stations (S1, S2) have apronounced imbalance in terms of load.Thus the station S1 is circulatingabout 63% of the load, while thestation S2 only 37%. 4.4. Supplying Network (injection andcontact) and sections of the structurehave a high load imbalance, bothbetween the two sources (S1, S2) andbetween sections, where the range ofvariation is between 3% (section 6)and 27% (section 1) of the total load.

All injection sections are underloaded, which is beneficial for thereliability and energy efficiency ofthem. Changes in the degree of loadingstations and sections of the supplyingnetwork reflects certain structurecharts and routes of transport, by thebeneficiary based on the necessity ofcommunity and economic efficiency fortransport operator. 4.5. Electrical load value (current,power) is highly variable, specific tothe driving power of vehicles. This isinevitable and it’s reflected by theincrease losses in transformers andpower network supplying, compared tothe case that the load would beconstant. 4.6. Consumption of power (energy) isbelow the reactive appropriate neutralpower factor, which implies an absenceof reactive energy bills. 4.7. The voltage harmonics inaccordance with the rules (THDU = 2.4%-station S1; THDU = 1.55% - stationS2). Harmonic current level is well abovethe limit indicated in the normative(THDI = 23% -station S1; THDI = 21.7% -station S2). These values of thecurrent harmonics reflect the poorsizing or downtime of the filter inthe recovery power of the twostations. The power effects of thecurrent harmonics (additional energylosses) are negligible due to the lowloading of the transformers. 4.8. Auxiliary power consumption inpower stations (S1, S2), of its ownservices (technological ownconsumption) is too high (22.83%)compared with normal values [(10-12)%]. Value of Auxiliary (WA) wasdetermined based on measurementsconcomitant - with its own meter andnetwork analyzer - in station S1. 4.9. Measurements and assessments madewith reference to the 3 types oftrolley buses, reflects the existenceof values close to the "efficiency"(η) for two types as follows:

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 200961% - trolley bus Saurer 560 GT; 60.7% - 212 E. ROCAR trolley bus A less sensitive (54.5%) was obtainedfor a trolley bus ROCAR 217 E. 4.10. For all of the 11 trolley busesfrom measurements and assessmentsmade, considering trolley busesequivalent of the same type, itobtains a good yield (60.46%) and showthat energy losses occur, mainly inthe mechanisms of transmission(22.53%) and engine (11.83%). 4.11. Based on records from October2008, it shows that the average numberof passengers transported is 196,which exceeds the amount recommendedfor the transport capacity of eachtrolley. Therefore, the 11 are loadedat the maximum. 4.12. The value calculated for thespecific energy consumption on” t km“determined based on AP is 132.8 Wh /t km. This value is below the valuespecified in the technical card oftrolley bus type ROCAR 212 E (160Wh /t km - at nominal load). This finding reflects a trolleybusesoperation at a normal level of energyefficiency. 4.13. For the entire contour, energyefficiency is about 39.4%, the largerenergy leak it is located in the undercontour of the supplying network andrecovery stations (34.85%) and not inthe vehicles (25.76%). This unusualstate is determined by excessiveauxiliary consumption of the recoverystations (22.83%). 4.14. Reducing energy consumption inthe analyzed outlines can be done byapplying the following technical-management measures: a) Replacement of the under loadedtransformers with transformers adaptedto the consumption; b) balancing the electric powernetworks (injection and contact); c) replacing less efficient trolleybus (ROCAR EDM 217 E) with aperformance one like (Saurer GT 560); d) reduction of the consumption in the

auxiliary rectifying stations.Measure b) is nonrealistic and istherefore not taken into account inpreparing the optimal balance. We further analyze the effect of othermeasures. a) The existing power transformers canbe replaced with 400 kVA transformers,appropriate to the loading level. Bythis measure we would achieve 50%reduction in loss of power transformersthat is an economy of 120,838 kWh/day,respectively 1058,541 MWh / year. Thismeasure is also economically feasible. c) By replacing ROCAR EDM 217 trolleybus with a trolley type Saurer GT 560we obtain increased efficiency of thetransport system (the 11 trolleybuses) from 60.46% to 60.9% and asaving of about 4,45 kWh / day, or38,982 MWh / year. This is feasible if the trolley busROCAR 217 E is towards the end of theperiod of useful life. d) reduction of auxiliary stationsrecovery from 22,83% to 12,83% lead toa substantial energy savings, namely:392,345 kWh/day, respectively,3436,942 MWh / year. 4.15. By applying the measures writtenabove, if the evoked results areobtain, we will have a PB optimum(fig.6)

Fig. 6 - Sankey diagram of optimal PB for the analysed contour

4.16. By applying specific measures to

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Analele Universităţii din Oradea Fascicula de Energetică, Vol. 15 2009achieve optimal PB we reduce theimpact on the environment by reducingthe quantities of pollutantsdischarged in the atmosphere [7].

REFERENCES

[1]. Berinde T. s.a., Întocmirea şi analizabilanţurilor energetice, Vol I si II. EdituraTehnică Bucureşti, 1976

[2]. Berinde T. şi Berinde M., Bilanţurienergetice în procese industriale, EdituraTehnică Bucureşti, 1985

[3]. Carabulea A., Carabogdan I. Gh,Modele şi bilanţuri energetice reale şi optime,Editura Academiei R.S.R., Bucureşti1986

[4]. Carabogdan Gh s.a., Bilanţuri energetice.Probleme şi aplicaţii pentru ingineri, Ed.Tehnică Bucureşti, 1986.

[5]. Duşa V., Bilanţuri şi optimizări energetice,Vol. I. Litografia IPT, 1990

[6]. Felea I., Dale E., Efecte ale RDN,Editura Universităţii Oradea, 2008

[7]. Felea I., Documentaţie privind auditulelectroenergetic la S.C. URBIS S.A. Baia-Mare,Oradea, 2009

[8]. ***Green Paper of Energy Efficiency or doingmore with less, Commission of the EuropeanCommunities, COM (2005) 256 final

[9]. ***Directive 2006/32/EC of the EuropeanParliament and of the Council on Energy and UseEfficiency and Energy Services, Commission ofthe European Communities

[10]. *** Legea nr. 199/2000 Privind utilizareaeficientă a energiei , publicata în MonitorulOficial al României, Partea I nr.734/2002

[11]. *** H.G. nr.339/2002 pentru abordareanormelor metodologice de aplicare a Legii nr.199/2000 privind utiliarea eficientă a energieipublicata în Monotorul Oficial alRomâniei, Partea I, nr. 229/2002

[12]. *** Ghidul de elaborare şi analiză a bilanţurilorenergetice, în conformitate cu ordinulARCE NR. 245

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