Rural Facility Electric Power Quality Enhancement

Electric power disturbances are known to be more prevalent in small, isolated power systems than in larger interconnected grids which service most of the United States. This fact has given rise to a growing concern about the relative merits of different types of power conditioning equipment and their effectiveness in protecting sensitive electronics and essential loads in rural Alaska. A study has been conducted which compares isolation transformers, voltage regulators, power conditioners, uninterruptible power supplies and indoor computer surge suppressors in their ability to suppress the various disturbances which have been measured in several Alaskan communities. These include voltage sags and surges, impulses, blackouts, frequency variations and long-term voltage abnormalities. In addition, the devices were also subjected to fast, high-magnitude impulses such as might be expected in the event of a lightning strike to or near utility distribution equipment. The solutions for power line problems will vary for different load applications and for different rural electrical environments. The information presented in this report should prove to be valuable in making the analysis.List of Figures - viii List of Tables - xiv Acknowledgements - xv Chapter 1: Electric Disturbances in Power Systems Introduction - 16 Categorizing Electrical Disturbances - 17 Voltage Disturbances and Transients - 19 Frequency Disturbances - 22 Sources of Transients - 22 Lightning and EMP - 23 Switching - 24 Power System Noise - 25 Common Mode and Normal Mode Noise Signals - 26 Chapter 2: Power Quality in Rural Alaska Characterizing the Village Power System - 28 The Village Electric Load - 29 Power Quality Site Surveys - 30 Rural Power Quality in Alaska - 31 Power Conditioning Requirements for Village Loads - 37 Chapter 3: Isolation, Voltage Regulation and Power Conditioning Introduction - 39 Slow Voltage Fluctuations - 39 Voltage Regulation and Power Conditioning - 40 Ferroresonant Transformers - 40 Electronic Tap-Changing Regulators - 44 Isolation Transformers - 47 Dedicated Lines - 51 Chapter 4: Impulse Suppression Introduction - 52 Surge Suppressors - 52 Surge Suppressor Components - 55 Component Configuration - 58 EMI/RFI Filters - 58 Standard Tests for Evaluating Surge Suppressor Performance - 60 Scope of Impulse Testing for Rural Alaska - 60 Impulse Test Equipment - 62 Test Procedure - 62 Impulse Testing Measurements - 63 Test Results - 64 Chapter 5: Uninterruptible Power Supplies The True UPS - 68 Standby Power Systems and a New Generation of UPS - 69 UPS Backup Time - 74 UPS Testing - 74 Chapter 6: Computers and Power Problems Introduction - 78 The Computer Tolerance Envelope - 78 Ridethrough - 80 Component Degradation and Equipment Failure - 82 Computer Power Supplies - 82 Linear Power Supplies - 83 Switching Power Supplies - 84 PC Tolerance of Powerline Disturbances - 84 Chapter 7: Comparing Power Conditioning Alternatives Voltage Regulation - 89 Isolation - 93 Uninterruptible Power Systems - 94 Computer Surge Suppressors - 98 Summary - 98 Appendices Appendix A: Voltage Clamping Levels of Surge Suppressors - 101 Appendix B: Voltage Clamping Levels of Power Conditioners and Uninterruptible Power Systems - 115 Appendix C: Noise Suppression of Surge Suppressors and Power Conditioners - 129 Appendix D: Waveforms and Regulating Characteristics of Power Conditioners and Uninterruptible Power Systems - 135 Appendix E: Comparison of Voltage Clamping Levels of Surge Suppressors Power Conditioners, Isolation Transformers and Uninterruptible Power Systems to High-Magnitude Impulse Voltages - 151 References - 16

Rural Facility Electric Power Quality Analysis

This report gives results of a recently completed data collection and analysis project investigating electric power quality of two isolated utility systems in Alaska. This is the second phase of a similar effort reported in 1984 which provided the first comprehensive power quality data from four small Alaskan communities. In this report, second generation instrumentation is described and comprehensive data and data analyses are presented. These data are important because of the increased use throughout Alaska of electrical and electronic equipment that may be damage by power system disturbances.Abstract - iv 1.0 Introduction - 1 1.1 Site descriptions - 1 1.2 Power quality definitions and disturbance analyzzer outputs - 2 2.0 Second Generation Instrumentation - 4 2.1 Hardware - 4 2.2 Software development and utilization - 8 3.0 Power System Disturbance Data - 9 3.1 Kotzebue site - 10 Figure Descriptions - 10 3.1.1 808: - 10 3.1.2 626: - 13 3.1.2.1 Impulse - 13 3.1.2.2 Sag - 16 3.1.2.3 Surge - 18 3.1.2.4 Frequency Disturbances - 21 3.1.2.5 Voltages - 23 Figures K1-K85 - 24-66 3.2 Tazlina site - 67 Figure Descriptions - 67 3.2.1 808: - 67 3.2.2 626: - 71 3.2.2.1 Impulse - 1 3.2.2.2 Sag - 74 3.2.2.3 Surge - 77 3.2.2.4 Frequency Disturbances - 81 3.2.2.5 Voltages - 83 Figures T1 - T102 - 85-135 3.3 Power system disturbance data summary - 136 3.3.1 Kotzebue site - 136 3.3.2 Tazlina site - 142 4.0 Conclusions - 147 5.0 Acknowledgements - 154 6.0 References - 154 7.0 Selected Bibliography - 155 8.0 Appendix

Anisotropic optical response of the diamond (111)-2x1 surface

The optical properties of the 2$\times$1 reconstruction of the diamond (111) surface are investigated. The electronic structure and optical properties of the surface are studied using a microscopic tight-binding approach. We calculate the dielectric response describing the surface region and investigate the origin of the electronic transitions involving surface and bulk states. A large anisotropy in the surface dielectric response appears as a consequence of the asymmetric reconstruction on the surface plane, which gives rise to the zigzag Pandey chains. The results are presented in terms of the reflectance anisotropy and electron energy loss spectra. While our results are in good agreement with available experimental data, additional experiments are proposed in order to unambiguously determine the surface electronic structure of this interesting surface.Comment: REVTEX manuscript with 6 postscript figures, all included in uu file. Also available at http://www.phy.ohiou.edu/~ulloa/ulloa.html Submitted to Phys. Rev.

Rural Alaska Electric Power Quality

Poor quality electric power has traditionally been blamed for electrical and electronic equipment malfunctions and failures in rural Alaskan communities. This report presents results of a recently completed project in which power system disturbance analyzers provide the first comprehensive power quality data from Alaskan villages. Power systems of four widely separated communities were studied for a total of 1,010 days. These results are important because of the trend in rural Alaska toward more sophisticated equipment that is sensitive to power system disturbances. These data represent a first step in developing appropriate countermeasures to protect electrical systems connected to isolated rural 60 Hz power generator facilitiesAbstract - 1 Introduction - 1 Site Identification - 4 Description of Disturbance Analyzer Measurement Capabilities - 6 Power System Disturbance Data Summary - 7 Established Limits of Acceptable Power Quality - 14 Methods for Improving Power Quality - 15 Effect of Low Voltage on Motor Operation - 16 Effect of Low Frequency on Motor Operation - 18 Conclusions - 19 Acknowledgements - 22 Implementation Statement - 23 References - 24 Figure Captions - 27 Figures - 2