Observations on APS feeder

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Observations on APS feeder

DSTAR Project P13-7Conservation VoltageReduction (CVR) Testingand Evaluationhttp://www.dstar.org


Background


Conservation Voltage ReductionReduce load demand and energy consumption bymodification of the feeder voltage profile• Exploits the sensitivity of load demand to supply voltageCVR Objectives• Reduce peak demand– Relieve generation, transmission, and possibly distribution capacity– Contingency relief, enhance bulk system reliability– Reduce production or purchase of high-cost energy• Decrease energy consumption– Reduce carbon and pollutant emissions– Meet policy goals– (May decrease utility revenue)Footer


CVR Factors• Variation of demand with voltage is a complexfunction of the specific characteristics of theconnected loads– Varies from feeder to feeder– Varies by time of day– Varies by season– Varies over time, in the long run• Variation of real and reactive demand to voltagechange is quite different• Real power CVR factor (CVR p ) is DP/DV• Reactive power CVR factor (CVR q ) is DQ/DVFooter


Determining CVR Factors• Laboratory measurement of representative individual loadCVR factors have been performed• However, bottoms-up determination of CVR factors isimpractical– Wide variety of loads– Utility does not know what loads and how much of each areconnected• Can be measured in the aggregate using long-term tests– Initial and steady-state effects of voltage reduction differ– Compare demand on alternate days with and without CVR– Painstaking process, unlikely to be performed but on a few circuits• Most of industry relies on published results– Beware of regional differencesFooter


CVR Factors – Temporal (Northwest)Source: NEEA DEI ReportIllustration of CVR factors measured in the Northwest• CVR factor curves do not mimic load profiles• CVR program may not necessarily need to operate during peak hours toachieve most energy savings62/15/2012


CVR Factors – Historical Trends2.52CVR p = ∆P∆V1.510.5y = -0.0086x + 18.014R 2 =0.8001970 1975 1980 1985 1990 1995 2000 2005 2010 2015-0.5CVR factor Averaged CVR Factor Linear (Averaged CVR Factor)• 109 samples by load research and pilot projects. Mean = 0.79• Most are residential and residential + light commercial, a few areindustrial loads.• No samples from the year 1992 to 2001.• Slight decline of CVR factor with time.72/15/2012


CVR Factors - DriversLoads are changing• Use of energy-efficientlighting has increased• Computers and consumerelectronics devices haveincreased and will beincreased furtherLightTVIncandescent(70W)CVRkWf = 1.44CRTCVRkWf = 1.0CFL(13W)CVRkWf = 0.74LCDCVRkWf = -0.02282/15/2012


CVR ImplementationStrategy• Reduce average service voltage• Maintain all service voltages above the minimum• Greatest average decrease without low voltage violationsrequires flattening the profile126VANSI C84.1 Range A Upper LimitOriginal profileFlattened and reduced profile120V114VANSI C84.1 Range A Lower LimitSecondary drop allowanceSubstationEnd-of-lineFooter


Reduce Substation Bus Voltage• On many feeders, there is sufficient voltage margin to simplyset the bus voltage lower– Especially short feeders• End-of-line voltage measurement can allow reduction of“safety margin”• Individual feeder regulators provide increased flexibility iffeeders have different voltage drops or load profiles126VANSI C84 Upper LimitLine-drop compensationEnd of line measurement120VSafety margin114VANSI C84 Lower LimitSubstationEnd-of-lineFooter


Reduce Impedance Voltage DropV drop ≈ I R ∙ R + I X ∙ XVoltage drop can be decreased by:• Improve the power factor• Balance circuits• Reduce load by shifting to other feeders• Reconductor• Convert single-phase to three-phase sections• Reduce length of circuit – avoid circuitous paths112/15/2012


Reactive Power FlowCapacitor Bank Application1.00.50.0SubstationEnd-of-lineBank size = 1/2 cumulative downstream kVAR• Capacitor banks are routinely used to correct power factor, reduce losses,and release capacity; also for voltage support• ½ kVAR rule commonly applied for loss minimization• Variation of reactive demand over the load cycle drives toward switchedbank application122/15/2012


Impact of Power Factor Correction onVoltage Profile• Feeders are typically not 100% compensated (1.0 pf)• A fully compensated feeder still has the I p *R drop• Finer compensation (more, smaller banks) gives flatter profile• Ultimate “flatness” requires overcompensation126VANSI C84.1 Upper LimitUncompensated feederCompensated feeder120VBus voltage reduced114VANSI C84.1 Lower LimitSafety marginSecondary voltage dropSubstationEnd-of-lineFooter


Overcompensated Feeder Profile• Overcompensated feeders maximize voltage profile“flatness” at the expense of greater loss• Banks must be switched to avoid excessive voltageduring lighter load126VANSI C84.1 Upper Limit120VOvercompensated feeder100% compensated feeder114VANSI C84.1 Lower LimitSafety marginSecondary voltage dropSubstationEnd-of-lineFooter


Voltage RegulatorsLine Drop Compensation126V120VSource: Electric Power Distribution HandbookANSI C84 Upper Limitw/o voltage regulatorw/ voltage regulatorRules of thumb for regulatorplacement:• One regulator – 3/8 of feeder• Two regulators: 1/5 and ½Line drop compensation enhancesCVR by providing only enoughboost as necessary114VANSI C84 Lower LimitSafety marginSecondary voltage dropSubstationVoltage RegulatorEnd-of-line152/15/2012


Voltage Regulator ControlEnd of Line Measurement (EOL)voltage regulatorSensor126V120VSource: Electric Power Distribution HandbookANSI C84 Upper Limitw/o voltage regulatorLine drop compensationEnd of line measurement• EOL allows more aggressive voltagereduction without ANSI limit violations• Install measurement at end of line at cost• May gain benefit by IVVC with availablemeasurementsGeneral Rule for Placement:Minimum voltage on its regulated area isequivalent to minimum voltage in itssource side114VANSI C84 Lower LimitSafety marginSecondary voltage dropSubstationVoltage RegulatorEnd-of-line162/15/2012


Integrated Volt-VAR ControlOptimizes status of regulators and switched capacitors toachieve objective function:• Minimized demand (CVR)• Minimum losses• Etc.A “SmartGrid” application requiring extensive communication• Central model-based control incorporated in DMS or in substationprocessor• Requires that capacitor and regulator controls accept remote commands• May monitor feeder voltage at numerous pointsFooter


Load BalanceCVR Implementation CostsEffect onVoltage ReductionHigh(>3V)Medium(1-3V)Load TransferAddingCapacitorsAddingVoltage RegulatorSystem improvements priority• Load transfer• Load balance• Add capacitors• Add voltage regulator• Add one or two phases• ReconductoringLow(


Challenges to CVR ImplementationCVR Roadblocks• Working between departments within utility• Possible loss of revenue because of energy efficiency measures• CVR increases frequency of occurrence and severity of voltage sags.• With the lower service voltage range, utilities have less flexibility tofurther reduce voltage during emergencies• Fear of customer complaintsEngineering Study Issues• Typical analysis evaluates primary distribution system only• Up-to-date power flow model may not be available• CVR factors of end-user loads are not typically available• Actual load allocation generally not known (including power factor)192/15/2012


Case Study


Study OutlineObject• Investigate impact of increasing levelsinvestment on CVR effectivenessApproach1. Identify and select representative feeders2. Apply various combinations of caps andregulators to condition feeder3. Apply CVR at peak to reduce demand4. Apply CVR over the year to reduce energy5. Assess cost-effectiveness of implementationon various feeders212/15/2012


Representative FeedersFeederTypeFeeder NameLoad TypeLoadPFPeak Load(MW)CustomerNumber3-ph FeederLength (mile)NominalVoltage(LL,KV)Rural Northwood Mixed 0.92 7.47 978 11.59 22.86Urban South Park Residential 0.83 7.06 479 2.38 13.2Suburban Indian Springs Residential 0.95 25.02 633 7.53 34.5Semi-rural Longview Commercial 0.95 16.21 86 4.9 12.47Suburban Pelham Commercial 0.90 9.97 311 3.36 12.47222/15/2012


Study ScenariosBase scenarioNo capacitor bank, no voltage regulatorSystem improvement scenariosFor PeakDemandReductionFor EnergyConsumptionReductionScenario Fixed Cap Bank Switched Cap Bank Voltage RegulatorP1 1P2 2P3 1P4 2P5 2 2E1 1E2 2E3 1 1E4 1E5 2E6 1 1 2• Assume secondary voltage drop is 4 volts.• Change tap to regulate the lowest voltage at 118V and fix the tap.• Assume CVRp = 0.8, CVRq = 3.5232/15/2012


Cap Bank & Voltage Regulator SitingOld LocationNew Location• Move cap bank near to the end of feeder• Site regulator to make lowest voltage in regulated area equal tosource side terminal voltage.242/15/2012


Peak Demand Reduction Comparison (Northwood)• The capacitor bank close to the end of feeder reducedvoltage drop more effectively, …enable more powerdemand reduction.252/15/2012


Peak Demand Reduction Comparison (Northwood)New Location• Siting caps and regulators for flattening voltage profile may incuradditional incremental losses.• Overall peak demand is generally reduced with incrementalinvestment.262/15/2012


Peak Demand Reduction (%)• Peak demand reduction varies substantially from feeder to feeder• Effectiveness of investment depends on feeder characteristics272/15/2012


Cost Table Used for the StudyCapacitor Bank Capital CostItem Company A Company B Company C Company D Company E Company F Average Cost without Outlier600 kVar SwitchedCapacitor Bank$38,321 (outlier) $7,385 $18,900 $11,574 $5,700 $12,000 $11,112900 kVar SwitchedCapacitor Bank$39,045 (outlier) N/A N/A $11,115 N/A $12,500 $11,8081200 kVar SwitchedCapacitor Bank$39,363 (outlier) $8,411 $19,200 $11,133 $6,500 $14,000 $11,849600 kVar FixedCapacitor Bank$4,694 (


Equivalent Generation Capacity CostEGCCCCap PWPRO&MEGCC = equivalent generation capacitor capacity cost ($/kW)C Cap = CVR implementation capital cost ($)PW O&M = present worth of O&M cost over the lifetime ($)P R = peak demand reduction by CVR (kW)Assumptions:• O&M cost present worth is over a 30 years life• Discount rate is 8%292/15/2012


CVR Implementation Cost EffectivenessExpensive ImplementationCompetitive ImplementationInexpensive Implementationong>Observationsong>:• Fixed capacitor is cost effective to enable peak load reduction via CVR.• One regulator could be a competitive approach for CVR implementation.• Two-regulator implementation when applied on a short feeder is expensive.302/15/2012


Feeder CVR Implementation FavorabilityLeast FavorableFeederLess Cost EffectiveLess EffectiveMost FavorableFeederong>Observationsong>:• High nominal voltage makes feeder desirable for CVR (Indian Springs).312/15/2012


Power Demand Reduction (kW)Energy Reduction Calculation160140t 0Process:1. Divide power reduction duration curve120100806040T* 1t 1T* 2t 2t 3200 1000 2000 3000 4000 5000 6000 7000 8000 9000Hour of a YearT* n-1t n-1T* nt n2. Calculate weighted average load demand3. Run load flow at the highest load demand4. Low feeder head voltage5. Run load flow at all load demand levels6. Calculate power reduction7. Extrapolate energy saving to one year• Time series simulation is a time-consuming process.• Power demand reduction duration curve simplified the calculation.322/15/2012


Energy Reduction (Northwood)Case NameBenefitCost of EnergyCapital Cost O&M AnnualAnnual Energy Energy Saved Energy SavedSaving($) Cost($) Cost($)(MWh) (MWh)(%)($/MWh)Base Case 38025 - - - - -One Fixed Cap Bank 37854 171 0.45 4,272 85 854 5.0Two Fixed Cap Banks 37833 192 0.50 8,544 171 1,709 8.9One Fixed and One Switched Cap 37664 362 0.95 16,080 322 3,216 8.9One Line Regulator 37452 573 1.51 48,510 970 9,702 16.9Two Line Regulators 37231 794 2.09 84,445 1,689 16,889 21.32Cap + 2Reg 37223 803 2.11 100,525 2,011 20,105 25.0IVVC 37038 988 2.61 N/A N/A N/A N/ACESFCR CCapES ACO&MCES = cost of energy saving ($/MWh)FCR = Fixed Charge RateC Cap = CVR implementation capital cost ($)AC O&M = O&M annualized cost ($)E S = energy saved (MWh)Assumption:• Fixed Charge Rate (FCR) is 0.18.ong>Observationsong>:• Annual energy consumption is reduced up to 2.61%.• The cost of energy saving is in the range of $5/MWh to $25/MWh.• Average LMP on wholesale market is around $50/MWh.• The cost of energy saving by CVR is cheaper than the average cost ofresidential electrical energy (~$113/MWh in 2009).332/15/2012


Thank You!


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Utilization VoltageService Voltage (120 – 600V)Service Voltage (> 600V)Utilization VoltageService Voltage (120 – 600V)Service Voltage (> 600V)Voltage LimitsStandards:The ANSI voltage standards (ANSI C84.1-1995)Normal OperationEmergency Condition• Providing service voltage within thelimits is the utility’s responsibility• Utilization voltage limits are thefacility’s responsibility• Range A is required for most servicevoltages for most of time – this is thearea where CVR can play127126120114+4.2%+5%+5%-5%+5%-2.5%+5.8% +5.8% +5.8%Nominal SystemVoltage-5%110-8.3%-8.3%108-10%Range ALimits for loads other than lighting-11.6%-13.3%Range B362/15/2012


Voltage LimitsSpecial Rules of Utilities10%132.0VService Voltage (V)Minimum MaximumAlabama 1 112.8 (-6%) 127.2 (+6%)Kentucky 2 108.0 (-10%) 132.0 (+10%)Connecticut 3 114.0 (-5%) 123.6 (+3%)5%0%-5%6%-6%10%-10%3%-5%10%-10%126.0V ANSI C84 Upper Limit120.0V114.0V ANSI C84 Lower LimitMississippi 4 108.0 (-10%) 132.0 (+10%)-10%Alabama Kentucky Connecticut Mississippi108.0V1. The limitations do not apply to special contracts in which the customer specifically agrees to acceptservice with unregulated voltage.http://www.psc.state.al.us/Administrative/sp-Rules.pdf2. A) For service rendered primarily for lighting purposes, variation in voltage between 5 p.m. and 11p.m. shall not be more than five (5) percent plus or minus the nominal voltage adopted, and totalvariation of voltage from minimum to maximum shall not exceed six (6) percent of the nominalvoltage.B) For service rendered primarily for power purposes, voltage variation shall not at any timeexceed ten (10) percent above or ten (10) percent below standard nominal voltage.http://www.lrc.state.ky.us/kar/807/005/041.htm3. After 1979. Prior to 1979, the voltage limits were -3% and +5% of nominal voltage.(Source: Conservation Voltage Reduction (CVR) at Northeast Utilities)4. http://www.psc.state.ms.us/executive/rules/rule25.html372/15/2012

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