Copper or galvanized steel for grounding strip?

This one's interesting, Mike. "Someone" gave you about 17 statements and got almost all of them wrong. I bet lots of us readers thought some of these were true ! I'm 65+ and tell my 20 year old proteges to study Grounding and Bonding, and when they figure it out, to please explain it to me! Grounding & Bonding is the "simplest" subject, yet, at the same time, can be the most difficult. We find grounding & bonding "issues" on almost every project we are asked to review, yet every one of these projects was "passed" by a local AHJ !

Mike, the NEC and it's confusing nomenclature about grounding and bonding seems to live on. The only place I can see that grounding is an issue to SPD's, is when they are protecting communications equipment from surges on external antennas. This is not a "premises SPD" as you aptly describe having little to do with earth ground at all. The communications SPD's however must have absolute minimal impedance and close proximity to earth ground in all cases. GPR/Ground Potential Rise from a nearby lightning strike causes a different kind of damage to communications equipment. Communications SPD's can "fire" in reverse (from the earth up, into coaxial communication lines). Much less voltage is involved in such reverse-firing of SPD's, but it is enough to wreak havoc with sensitive equipment. The only thing (besides fiber optic isolation) that prevents damage from GPR, is fast-acting ground systems that maintain equipotential by means of impecable bonding. The premises main disconnect grounding electrode must also be bonded to the antenna fields and their grounding system in order to minimize damage from GPR. This does give premises SPD's a workout when the antenna fields are taking hits!

I am a very bisy guy. I was interested in your topical discussions but I really dont have the time for a long version . How 'bout just writing the bare facts of what your trying to get across to us. For myself this would be a great advantage. Thanx for the info

You take grounding vs bonding very seriously don't you? Thank-you for clearing up that issue in my mind. I, too, have used the term "ground" and "bond" loosely and have interchanged them with no regard to meaning. I, now, have a greater appreciation for the meaning of these terms and I am sure I will not confuse them again!!!:) That was a very good correction of a poorly written article!!!

Mike:

Who since the comments concerning SPD grounding in the IEEE C62.72 document?? Please advise. If any person has such misunderstanding of the document and such strong negative comment, then their name and E-MAIL address should be known. Also, it provides an opportunity to invite them to the next IEEE/SPDC meeting.

Mike: Apparently this is proposed text in an upcoming IEEE standard, which I find troubling. The text is very poorly written with regards to what they are trying say and use of industry terms. An example of poorly written language:

"It is therefore recommended that the resistance, between the equipment to be protected and the main grounding electrode, should be 1 ohm or less at the time of installation."

The way I interpret this is that the Grounding Electrode Conductor should be 1 ohm or less, not the actual Grounding Electrode ground resistance. Maybe they were talking about the resistance of the grounding electrode conductor, but the following paragraphs lead me to believe they were trying to make a recommendation on the grounding electrode ground resistance. To make a recommendation concerning the ground resistance of the grounding electrode, to me should require some research to back that up. Why not 5 ohms or 2 ohms, where does the 1 ohm come from? Then they should put that recommendation in the proper standard which is IEEE 142 (the Green Book) and IEEE 1100 (the Emerald Book). Plus I completely agree with your rebuttal, grounding electrode ground resistance plays no part in the effectiveness of an SPD (at least not the parallel connected type such as MOV's).

I think they were trying to address extended overvoltages which are a major cause of MOV SPD failures. But again, since it is so poorly written, it's hard to tell what they were trying to say. I wish the authors of these types of standards would use industry defined terms consistantly and be more precise in their language.

Thanks for your efforts to improve our industry, Jeff Sobczyk

I am working on a grounding and bonding test procedure for a military project and am finding a lot of contradictions and confusion between the different standards. What would help immensely would be if IEEE, NFPA and the military standards would not only standardize terminology, but standardize the scope of the different grounding and bonding systems. Here are some suggestions. Each of these systems should be addressed in a separate section of NFPA 70 Article 250. Notice that I intentionally avoid the word "ground".

Systems: Earth Electrode Systems Bonding for Lightning Protection Bonding for Fault Protection Bonding for Static Electricity Charge Dissipation Bonding for Hazardous Materials (Classified) Areas Bonding for Sensitive Electronic/Communication Equipment Bonding for EMI Shielding (cabling and enclosures)

Equipment: Earth Electrode Lightning Electrode Conductor - connection to electrode Lightning Bonding Conductor - connection between terminals Lightning Bonding Jumper - connection to metal objects Fault Electrode Conductor - connection to electrode Fault Bonding Conductor - green wire connection to equipment Fault Bonding Jumper - connection to equipment enclosure Common Conductor - white wire neutral/grounded conductor Common Electrode Bond - single point earth reference Static Jumper/Whip - connection to equipment/personnel Static Plate - accessible bus bar/point of connection Static Bonding Conductor - connection to structure/flooring Static Electrode Conductor - connection to electrode Isolated Bonding Conductor - connection to sensitive equip Cable Bonding Jumper - cable shield connection

It is interesting to compare the requirements of the following standards, which sometimes completely contradict each other: DA PAM 384-64, Ammunition and Explosives Safety Standards MIL-HDBK-419, Grounding, Bonding, and Shielding for Electronic Equipments and Facilities - Vol 1 Basic Theory; Vol 2 Applications MIL-STD-188-124, Grounding, Bonding and Shielding for Common Long Haul/Tactical Communication Systems Including Ground Based Communications-Electronics Facilities and Equipments MIL-STD-1542, Electromagnetic Compatibility and Grounding Requirements for Space System Facilities DOE M 440.1-1A, DOE Explosives Safety Manual AFI 32-1065, Grounding Systems (including supplement) AFJMAN 32-1082, Technical Manual - Facilities Engineering Electrical Exterior Facilities AFM 91-201, Explosives Safety Standards IEEE Std 81, IEEE Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Ground System IEEE Std 142, IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems NFPA 70, National Electrical Code NFPA 70B, Recommended Practice for Electrical Equipment Maintenance NFPA 77, Recommended Practice on Static Electricity NFPA 780, Standard for the Installation of Lightning Protection Systems

The MH Newsletter is an excellent mechanisim for improving the knowledge of electricians at all levels. Grounding and bonding articles, in my opinion, are coming up short. Some comments are sometimes confusing to me unless I take the time to carefully assimilate. I know most electricians will not take the time to assimilate and understand. So, what do I suggest? For example, this article about SPD's might incorporate sketches showing the relationship of the SPD to the windings at the source. It may help understand why earth ground is not involved. Keep up the good work.

Mike, is there any way to prevent this misinformation from going out? We seem to be going backwards. How can these guys be so ignorant? Karl

Mike,

Most hardwired surge protectors do provide protection against lightning surges a.k.a. common mode surges which does require a good connection to earth. However, they will always do a better job of limiting the voltage from the hot wires to the equipment grounding and bonding grid than to earth ground.

A new 2005 NEC requirement that surge arrestors and transient voltage surge suppressors for use on ungrounded systems be rated for the purpose.

I also have had experience with both 277Y480 volts solidly grounded and 480 volts ungrounded. The 480 volt ungrounded systems in question did not have ground detectors at one company at at the other company ground detectors were connected. 480 volts ungrounded that has no ground detectors has extremely high rates of motor and power electronics damage due to buildup of excessive static electricity during rain storms. There is just no comparison with solidly grounded systems. This is due in part to Saint Elmo's Fire which is a more or less steady trickle of electricity form cloud to ground. This trickle of charge can prematurely wear out SPDs. Saint Elmo's Fire is what Benjamin Franklin really picked up with his kite experiment and if he had picked up anything stronger he would have been toasted.

Ground detectors on ungrounded systems do play a role in getting rid of excess static charge. This is particularly true of 3 control transformers ( primary side phase to ground ) with 130 volt light bulbs on the secondaries.

Mike Cole mc5w at earthlink dot net

Mike I find the same type of mistakes and misunderstanding of Grounding/Bonding in other articles and books as well. This is different though, as one would think that someone from IEEE is editing or at least proof reading this first. I hope the paper does not get printed is about all I can ask for.

Pierre

I contacted IEEE, of which I'm a Senior member, and suggested they review the wording of the proposed standard. The response I got was as follows:

"Jim, there's really no reason we can't fix this before the document goes to ballot. Since the WG opted to submit the document "as is" based on text from the previous recirculation a few years back, it will require quorum approval from the working group to make any edits. I have requested that [name deleted] (new 3.6.6 chair) obtain that input as expeditiously as possible so we can review some potential text edits and get them incorporated prior to balloting."

Committees are usually wrong, but here they seem to be trying to state a more general truth than Mike would like to read into it. Are both actually talking about the same thing? What purpose is accomplished by combining IEEE ‘standards’ and the NEC? They aren’t the same subject. The debate on the nature of ‘grounding’ goes far beyond the scope of the NEC. Mike is correct for specific 'brands' of SPD's on the market but not for all surge protection schemes in use. Perhaps a brief explanation of the equipment being referenced would clear up the discrepancy. Contemporary commercial surge protection equipment functions within a limited range and useful only if engineered for a specific application. Surge equipment that is inadequate in the case of a maximum event is as useless as surge equipment that is never needed. MOV's work and are cheap but they have limited life expectancy requiring costly monitoring circuitry and/or regular maintenance. The most extensive (explosive) surge damage I have seen entered the system via the bonding conductor. The single most costly surge damage event entered through a telephone line. If that line had MOV’s paralleled to ground there would have been no damage other than to the MOV’s.

Very well said by JD Miskell. NEC bonding requirements are intended to provide safe operation and very limited protection from lightning events. Even the referenced NFPA 780 recommendations cover just bare minimums of generally accepted protection levels for life or property from lightning. I think its fair to expect that NEC-250 bonding requirements avoid any implication of lightning safety, just as NFPA 780 avoids electrical safety compliance issues. The two compliment each other, neither tries to be the end-all of bonding or grounding.