The EPRI DPQ Project

In order to better understand the statistics of rms voltage variations, as well as other power quality phenomena, the Electric Power Research Institute (EPRI) conducted a power quality monitoring survey of 277 monitoring locations located on the primary distribution feeder of twenty-four electric utilities across the United States. Commonly known as the Distribution System Power Quality Monitoring Project, or the EPRI DPQ Project, the study spanned the period from June 1993 to September 1995. It resulted in the collection of over 6.8 billion samples from PQNode power quality monitors. The samples are stored today in a 46GB database managed by PQView. The project’s final report focused on statistics related to rms variations (i.e., voltage sags and interruptions), transient overvoltages, voltage & current harmonic distortion, steady-state voltage regulation, and voltage unbalance.

The EPRI DPQ Project was conducted from 1990 to 1995. The main contractors for the project were Electrotek Concepts and Basic Measuring Instruments, which is now Dranetz. It was a multi-phase, multi-year effort involving twenty-four EPRI member utilities.  

The EPRI DPQ Project had numerous major deliverables: 
  • Development and commercialization of a new power quality monitoring instrument called the PQNode® and its management and analysis software, PASS®
  • Guidelines for monitoring distribution system power quality events in EPRI TR-103208, A Guide to Monitoring Distribution System Power Quality
  • An executive summary report on the project: EPRI Report 1017340: DPQ Executive Summary
  • A report on the statistics of voltage sags, transients, harmonic distortion, and unbalance from the distribution monitoring locations of the EPRI DPQ Project, which is available in EPRI Report 1017341: An Assessment of Distribution System Power Quality, Volume 2: Statistical Summary Report
  • Guidelines for simulating distribution system power quality events and cold load pickup in EPRI TR-106297The Distribution System Modeling Guide for Disturbances and Cold Load Pickup 
  • Extensive collection of power quality disturbance case studies illustrating waveforms that can be used as signatures for recognizing similar events in EPRI TR-106294-V3: Library of Distribution System Power Quality Monitoring Case Studies. Some of these events of the month can be downloaded as EPRI Reports, including Reports 1017236, 1017233, 1017229, and 1017221.
  • A distribution system power quality database with millions of power quality measurements called the EPRI DPQ Database. The database was built using PQView 1.4 and is maintained today by PQView 3.
  • The power quality database management and analysis system called PQView®, which is use today by nearly one hundred companies worldwide to manage data from more than fifty data sources. 
The chief goal of the project was to provide baseline statistics regarding quantities from the following types of measurements recorded by the PQNode 8010:
  • RMS Voltage Variation: voltage sags, voltage swells, momentary interruptions, undervoltages, and overvoltages, beginning of sustained interruptions
  • Waveshape Fault: transients, beginning and end of faults,
  • Impulse: high-frequency transients with above 5 kHz
  • Outage: sustained interruptions
  • Cold Load Pickup: inrush current at breaker recloser due to an outage
  • Steady-State Sample: regulation, voltage and current unbalance, power and power factor, harmonic distortion, voltage notching
  • Steady-State RMS Envelope: voltage regulation, load cycles, frequency, monitor internal temperature, voltage and current rms variations

Host Electric Utility Systems for the EPRI DPQ Project

The project utilized the participation of twenty-four electric utility companies across the United States to provide geographic and operating practice diversity. The site selection process resulted in the selection of 300 monitoring sites within the service territories of the electric utilities in the following list:
  • Boone Electric Cooperative
  • Chattanooga Power (now EPB)
  • Cincinnati Gas & Electric (now Duke Energy)
  • Connecticut Light & Power (Northeast Utilities)
  • Delmarva Power (now Conectiv)
  • Duke Power Company (now Duke Energy)
  • East Kentucky Power Cooperative
  • Elizabethan Electric
  • Empire District Electric Company
  • Florida Power Corporation (now Duke Energy)
  • Georgia Power Company (Southern Company)
  • Gibson Electric Membership Corporation
  • Houston Lighting & Power (now Reliant Energy)
  • Illinois Power (now Ameren)
  • Kansas City Power and Light Company
  • KPL Gas Service
  • Long Island Lighting (now LIPA)
  • Los Angeles Department of Water & Power
  • Massachusetts Electric (now National Grid)
  • Pacific Gas & Electric
  • Public Service Gas & Electric
  • Rochester Gas & Electric
  • Sierra Pacific Power (now NV Energy)
  • Snohomish County PUD

The Kansas Electric Utilities Research Program (KEURP) indirectly supported the project via participation of Empire District Electric Company and KPL Gas Service. The Tennessee Valley Authority (TVA) indirectly supported the project via participation of Chattanooga Power, Elizabethan Electric, and Gibson Electric Membership Corporation.


Each feeder selected for the EPRI DPQ Project was monitored in three locations. (Photo courtesy of PG&E) 

To Learn More

This is a chronological list of the technical papers, reports, and magazine articles written by the many people who worked on the EPRI DPQ Project.  

  1. H. Mehta, J. C. Smith, J. L. Thompson, "Important Power Quality Concerns on the Supply Network." Proceedings: 1st International Conference on Power Quality: End-Use Applications and Perspectives (PQA’91), Paris, France, October 1991.
  2. E. W. Gunther, J. L. Thompson, R. V. Dwyer, H. Mehta, "Monitoring Power Quality Levels on Distribution Systems." Proceedings: 2nd International Conference on Power Quality: End-Use Applications and Perspectives (PQA’92), Atlanta, Georgia, October 1992.
  3. L. C. Markel, C. J. Melhorn, S. R. Williams, H. Mehta, "Design of a Measurement Program to Characterize Distribution Power Quality." Proceedings: 12th International Conference on Electricity Distribution (CIRED’93), Birmingham, England, May 1993.
  4. E. W. Gunther, D. D. Sabin, H. Mehta, "Update on the EPRI Distribution Power Quality Monitoring Project." National Conference on Power Quality: End-Use Applications and Perspectives (PQA’93), San Diego, California, October 1993
  5. W. W. Dabbs, D. D. Sabin, T. E. Grebe, H. Mehta, "Probing Power Quality Data." IEEE Computer Applications in Power, May 1994.
  6. S. R. Kaprielian, A. E. Emanuel, M. F. McGranaghan, R. V. Dwyer, H. Mehta, "Predicting Voltage Distortion in Systems with Multiple Harmonic Sources: A Probabilistic Approach." IEEE Transactions on Power Delivery, July 1994.
  7. R. C. Dugan, L. Ray, D. D. Sabin, G. Baker, C. Gilker, A. Sundaram, "Impact of Fast Tripping of Utility Breakers on Industrial Load Interruptions." Conference Record of the 1994 IEEE Industry Applications Society Annual Meeting, Denver, Colorado, October 1994.
  8. D. D. Sabin, T. E. Grebe, S. R. Baird, A. Sundaram, "Preliminary Results from the EPRI Distribution Power Quality Project." Proceedings: 3rd International Conference on Power Quality: End-Use Applications and Perspectives (PQA’94), Amsterdam, Netherlands, October 1994.
  9. E. W. Gunther, H. Mehta, "A Survey of Distribution System Power Quality - Preliminary Results." IEEE Transactions on Power Delivery, Vol. 10, No. 1, January 1995.
  10. D. D. Sabin, T. E. Grebe, A. Sundaram, "Preliminary Results for Eighteen Months of Monitoring from the EPRI Distribution Power Quality Project." Proceedings: 4th International Conference on Power Quality: End-Use Applications and Perspectives (PQA’95), New York, New York, May 1995.
  11. D. D. Sabin, T. E. Grebe, A. Sundaram, "Surveying Power Quality Levels on US Distribution Systems." Proceedings: 13th International Conference on Electricity Distribution (CIRED’95), Brussels, Belgium, May 1995.
  12. D. D. Sabin, T. E. Grebe, C. J. Melhorn, A. Sundaram, "Distribution Power Quality Measurement Program," 48th Power Distribution Conference, October 1995, Austin, Texas.
  13. G.T. Heydt, E. W. Gunther, "Post-Measurement Processing of Electric Power Quality Data," IEEE Transactions on Power Delivery, 96 WM 063-8 PWRD.
  14. D. D. Sabin, A. Sundaram, "Quality Upgrades Reliability," IEEE Spectrum, February 1996.
  15. D.D. Sabin, D.L. Brooks, A Sundaram, "Indices for assessing harmonic distortion from power quality measurements: definitions and benchmark data," IEEE Transactions on Power Delivery, vol.14, no.2, pp. 489-496, Apr 1999.
  16. D. D. Sabin, T.E. Grebe, A. Sundaram, "RMS voltage variation statistical analysis for a survey of distribution system power quality performance," Conference Proceedings of IEEE Power Engineering Society 1999 Winter Meeting, IEEE , vol.2, no., pp.1235,1240 vol.2, 31 Jan-4 Feb 1999.
  17. D. D Sabin, T.E. Grebe, D.L. Brooks, A. Sundaram, "Rules-based algorithm for detecting transient overvoltages due to capacitor switching and statistical analysis of capacitor switching in distribution systems," Proceedings of 1999 IEEE Transmission and Distribution Conference, vol.2, no., pp.630,635 vol.2, 11-16 Apr 1999.

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