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
