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Understanding Power Factor: Efficiency Implementation and Correction Case Studies

Learn about the importance of power factor in using electrical power efficiently through case studies and penalty examples. Discover how to improve power factor with capacitor sizing and its benefits.

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Understanding Power Factor: Efficiency Implementation and Correction Case Studies

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  1. 2008 DTE/ESD Energy Conference and Exhibition • Energy Efficiency Implementation Case Study • Power Factor Correction Case Study • Power Overview • Power Factor Penalties • Case Study • May 6, 2008 www.myronzucker.com

  2. What is Power Factor Power Factor is a measure of how effectively power is used Inductive loads require two types of power to operate: Active Power Apparent Power Reactive Power Active Power – Performs the work Reactive Power – Maintains the electro-magnetic field Apparent Power – Vector sum of Active and Reactive power www.myronzucker.com

  3. What is Power Factor Vector summing power Active Power kW θ 90˚ Reactive Power kVAr Apparent Power kVA Power factor is the ratio of kW to kVA Power factor is the ratio of active power to apparent power kW kVAr = pf cos θ = pf = θ arctan kVA kW www.myronzucker.com

  4. What is Power Factor The Difference Perfect Power Factor Poor Power Factor Good Power Factor kW kVAr = 0 θ = 0 > 32˚ < 32˚ kVA No Penalty kVAr kVA Unity kVA kVAr Penalty kW 0 kVAr > .85 = 1 < .85 cos θ < .85 cos θ > .85 cos 0 = 1 = 0 > 32 < 32 arctan kVA kW kW www.myronzucker.com

  5. Power Factor Penalty Example of DTE penalty rates (issued January 1994) • Penalty is applied to all metered quantities • Power Factor less than .700 is not permitted and corrective equipment must be installed. • 25% penalty applied after two consecutives months below .700 www.myronzucker.com

  6. Power Factor Penalty The Mechanics of Power = kW = kVAr The Utility Company Your Facility www.myronzucker.com

  7. Power Factor Penalty The Mechanics Without Capacitors The Mechanics With Capacitors Power Factor = .80 Power Factor = .89 400 kW 1% Penalty 447 kVA 500 kVA 100 kVAr 200 kVAr Your Capacitor Bank Catches and stores the kVAr before it gets back on to the utilities grid 300 kVAr The Utility Your Facility www.myronzucker.com

  8. Power Factor Penalty Example of DTE Utility Bill www.myronzucker.com

  9. Power Factor Penalty Example of DTE Utility Bill kVARH = 1,103,200 kWH = 1,235,920 kWH = 1,235,920 kVARH = 1,103,200 kVAH = 1,656,668 kW = .746 kVA www.myronzucker.com

  10. Sizing Power Factor Capacitors www.myronzucker.com

  11. Sizing Power Factor Capacitors Avg Kilowatthours Used Per Day This Period 22,519 KWH Average kW = 22,519 / 24 = 938 kW = 938 θ kVAr = 837 kVA = 1,257 Avg Kilowatthours Used Per Day This Period 22,519 KWH 938 * 0.398 = 373 or 375 kVAR required to improve power factor from .75 to .90 www.myronzucker.com

  12. Sizing Power Factor Capacitors Information Required to Size and Locate Capacitors • 12 months of electrical utility bills • Electrical layout of facility • Motor location and sizes • Transformer sizes • Variable Frequency / Speed Drives • Harmonic study www.myronzucker.com

  13. Case StudyOaks Correctional FacilityManistee, Michigan • 4 housing units; 4 large buildings which include food services, health care, recreation, maintenance, warehouse storage, administrative offices. • HVAC, compressors, lighting, hydraulic motors • Poor power factor • $650 average power factor penalty/month www.myronzucker.com

  14. Case StudyOaks Correctional Facility Solution for Oaks Correctional Facility • 320 kVAr was calculated for facility to reach the target power factor • 30 kVAr installed at the switchgear in each of the 4 housing units • 50 kVAr capacitor installed at the switchgear in each large building • Total cost of capacitors: $6000 • Penalty eliminated plus rebate of $200/month = $850 savings/month • Payback of less than one year achieved, even considering installation costs. www.myronzucker.com

  15. Benefits of Improving Power Factor • Elimination of Power Factor Penalties • Where applicable • Increase Capacity in Electrical System • Reduction of I2R Losses • When capacitors are located close to inductive load • Up to 4% savings for that load • Improves Voltage on System www.myronzucker.com

  16. Power Factor Capacitors • Capacitor Tolerances • United States: IEEE 18-2002 • Capability • Line to Neutral 110% Continuous • Line to Line 120% Continuous • Current 180% Continuous • Var Output 135% Continuous • Europe: CE Standards call for 8 hour period • Remember that these standards are Recommendations, not Code, and can therefore be ignored by manufacturers www.myronzucker.com

  17. Power Factor Capacitors • Electric Power Research Institute (EPRI) • “You can only save energy that is wasted” • Infrastructure (system) losses generally 1-4% • Includes I2R losses (Line Losses) • Beware of large energy saving claims where capacitor are used • Claims of large savings on your “losses” is NOT equal to large savings on your entire energy bill. A claim of 15% savings on energy “losses” at a facility with 2% line losses would total at most a .3% savings on the entire energy bill. (e.g. 15% x 2% = 0.3%) www.myronzucker.com

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