Here are five key revisions to this IEEE standard, some of which are in response to manufacturer and end user concerns. The upcoming version demonstrates that its working group is able to stay current in the ever-changing power quality field.
Yes, the Emerald Book is being updated "as we speak." One of the few reputable standards covering power quality, ANSI/IEEE 1100 (Recommended Practice for Powering and Grounding Electronic Equipment) will reflect newer thinking on grounding technologies, products, and methods. So what are some of the key revisions? Read on and find out.
Revision 1: No more "sensitive" equipment. You'll notice the word "sensitive" is not in the standard's title, as noted above. That's because the Emerald Book committee, in one of its first changes, struck the word from the title. Why? Most equipment manufacturers don't like their equipment referenced as "sensitive," especially to its installed electrical environment. In fact, some electronic equipment manufacturers suggest the 1992 edition of the Emerald Book isn't applicable to their equipment, specifically because "their equipment isn't sensitive." So rather than come up with a definition for the word "sensitive" (as it applies to electronic equipment), the committee decided striking the word from the title was easier. They also rewrote all references worded as "sensitive electronic equipment" to reflect this change.
Revision 2: Voice/data equipment added. Chapter 10 (Information Technology Equipment) is a significant addition. This chapter offers basic insight into power quality issues affecting data and voice equipment. Some participants to the standard thought the 1992 version was as applicable to telecommunication equipment as other electronic equipment. But telecommunication equipment environments (and the equipment itself) are more dynamic than standard industrial or commercial electrical environments. Wiring topologies, equipment protection practices, and component definitions are just some of the topics discussed.
Revision 3: No more "TVSS." This acronym for transient voltage surge suppressor changes to "SPD," which denotes surge protection device. Here's why. When you mention a TVSS, most people envision a surge suppressor made up of metal-oxide varistors, or MOVs. In reality, there's a wide variety of surge protection devices available, some of which have nothing more than inductors in series with the circuit conductors. Also, the word "suppressor" itself seems to indicate these devices (ones with inductors) eliminate surges present on wiring and grounding systems. The thinking is: People who apply such a device may be disappointed with the results.
Revision 4: No more 0.25-ohm maximum for equipment grounds and neutral. Gone is the Chapter 6 (Site Surveys and Site Power Analyses) recommended maximum value of 0.25 ohms for equipment grounding and neutral conductor impedances. The 1992 edition's recommendation states:
Properly installed and maintained equipment grounding conductors will exhibit very low-impedance levels. Recommended practice is to verify impedance levels of 0.25V or less. This will also help assure personnel protection under fault conditions.
The committee deleted this because there's no basis for recommending such an exact value, especially for an equipment grounding system. Overcurrent devices in some systems need less than 0.25 ohm in the equipment grounding system to operate promptly. Rather than remove the 0.25-ohm criteria without follow-up, the committee added a chart to use as a guide for equipment grounding impedances.
Chapter 6 also includes criteria for two-point bonding measurements using a three- or four-terminal earth ground resistance tester.
Revision 5: New power line monitoring techniques and even an EPRI study. Expanded, Chapter 6 now reflects proper power line monitoring techniques for various electrical configurations. Also, Appendix A of the standard now includes a power quality study written by current members of the Electrical Power Research Institute (EPRI). A good supplement to the Emerald Book, this study gives experts and novices in the power quality field insights into trends and causes of power quality problems occurring nationwide.