Control System Power and Grounding Better Practice (eBook)

Cover 1
Contents 6
Introduction 12
CE Statement 12
Warnings, Cautions, and Notes 13
Liability 13
Chapter 1. Site Preparation Overview 14
System Availability 14
Impact of New Technologies on System Availability 15
Importance of Mean Time to Repair 15
Electrical Noise Influences 16
Minimizing Influences 16
AC Power Considerations 17
System Ground 18
Earth Ground 18
Signal Wiring for Traditional I/O Systems 19
Signal Wiring for I/O Bus Systems 20
Intrinsically Safe I/O Systems 20
Lightning Protection 21
Chapter 2. AC Power Distribution 22
AC Power Considerations 22
AC Distribution System 25
AC Power Supply Connections 32
Workstations and Peripheral Equipment 35
Auxiliary Equipment 36
Chapter 3. DC Power Distribution 38
DC Power Considerations 38
DC Power Connections 38
Bussed Field Power 40
Resistor-Capacitor Snubbers 43
Intrinsic Safety Considerations 43
Chapter 4. System Grounding 44
Single-Point Ground Techniques 44
Enclosure Ground Considerations 49
Effective Grounding 50
Using Existing Ground Systems 50
Separating AC and DC Grounds 51
Ground Wiring 53
Shield Grounds 56
Workstations and Peripheral Devices 57
AC/DC Controller and I/O Power Supply 57
DC/DC Controller and I/O Power Supplies 59
Bulk Power Supplies 60
Redundant Power Connections 60
Intrinsic Safety Installation Grounding 63
Chapter 5. Signal Wiring 64
Signal Wiring Practices 64
Electromagnetic Interference (EMI) Reduction 65
Protection from AC Power Line Noise 67
Direct Cable Runs 68
Multi-Pair Cable Runs In Junction Boxes 68
Low-Level Signal Cable Runs in Junction Boxes 71
Class 1 Division 2 Recommendations 72
AS-Interface Considerations 73
DeviceNet Considerations 75
FOUNDATION Fieldbus Considerations 77
Profibus Considerations 79
Chapter 6. Alarm Wiring 82
Chapter 7. Earth Ground 84
Designing an Earth Ground 84
Testing an Earth Ground 90
Annual Inspection 93
Chapter 8. Lightning Protection 94
Reference Documents 94
Lightning Risk Determination 94
Lightning Protection Systems 95
Implementing Lightning Protection 98
Inspection of Lightning Protection Systems 99
Appendix A. Variable Speed Drive Considerations 100
Recommendations 100
Electrical Noise Examples 102
Ground Considerations 103
Motor Ground Connections 105
VSD Cable Specifications 107
Critical Cable Lengths 107
Appendix B. Testing with an Oscilloscope 110
General Monitoring 110
Fieldbus Segment Monitoring 111
Appendix C. Wire Size and Color Codes 112
Index 114