CP 3050 Recommended Revisions
CP 3050 recommended the following changes to the wording in NESC 2007:
“444.D Employee’s protective grounds
“When all designated switches and disconnectors have been operated, rendered inoperable where practical, and tagged in accordance with Rule 444C, and the employee has been given permission to work by the designated person, the employee in charge should immediately proceed to make the employee’s own protective grounds or verify that adequate grounds have been applied (see Rule 445) on the disconnected lines or equipment. During the testing for potential and/or application of grounds, distances not less than those shown in Tables 441-1 to 441-3, as applicable, shall be maintained.
“Temporary protective grounds shall be placed at such locations and arranged in such a manner that affected employees are protected from hazardous differences in electrical potential.
“Note: Hazardous touch and step potentials may exist around grounded equipment or between separately grounded systems. Additional measures for worker protection may include barriers, insulation, isolation or grounding mats.
“The distance in Table 441-1, 441-2, or 441-3, as applicable, shall be maintained from ungrounded conductors at the work location. Where the making of a ground is impractical, or the conditions resulting there from are more hazardous than working on the lines or equipment without grounding, the ground may be omitted by special permission of the designated person.
“Exception: Alternative work methods such as isolation of equipment, lines, and conductors from all sources including induced voltages may be employed when the employer has assured worker protection from hazardous differences in electrical potential.”
Reasons for Change
The first recommended change, found in the first paragraph, was made simply to correct an editorial error. I am still not sure what a “disconnector” is, and I tried as a voting subcommittee member to get it changed to “disconnects,” but I – as well as several other subcommittee members – was outvoted.
The total deletion and replacement of the second paragraph was done to remove an outdated and incorrect method of installing temporary grounding for worker protection. The replacement paragraph is from OSHA 1910.269(n)(3). OSHA’s paragraph is what is called a performance standard, meaning OSHA is not specifying a particular method of grounding, but requiring temporary protective grounds be installed in a method and manner that protects workers from hazardous potentials or voltages. If an employer has lots of money and a large test lab full of engineers, the employer can develop a unique temporary protective grounding method they have proven, through testing, provides protection for their workers on their system. If the employer does not have lots of money, the employer must rely on industry standards, guides and peer-reviewed papers. Such documents include:
• IEEE 1048, “Guide for Protective Grounding of Power Lines”
• IEEE P1246, “Guide for Temporary Protective Grounding Systems Used in Substations”
• AIEE 54-206, “Placement of Protective Grounds for the Safety of Linemen”
• IEEE 88 SM 558-9, “Test Results of Personal Protective Grounding on Distribution Line Wood Pole Construction”
• IEEE ESMOL Subcommittee 15.07, “Worker Protection While Working De-energized Underground Distribution Systems”
The newly added note warns of potentially hazardous touch and step potentials around grounded equipment (vehicles), conductors, cables and electrical equipment not electrically bonded together to create an equipotential zone. The note goes on to offer options such as barriers, insulation, isolation or grounding mats to provide worker protection.
The new exception suggests the use of the isolation work method where the insulation or equipotential grounding method is difficult to use. The isolation method is most often used in underground electrical systems.
CP 3051 Recommended Revisions
CP 3051 recommended the following changes to the NESC 2007 wording of Section 445.A & B:
“445. Protective grounds
“Extreme caution shall be exercised that the proper sequence of installing and removing protective grounds is followed.
“A. Installing grounds
When installing protective grounds on a previously energized part, the following sequence and precautionary measures shall be observed.
“Exception: In certain situations, such as when grounding conductors are supported on some high-voltage towers, it may be appropriate to perform the voltage test before bringing the grounding device into the work area.
“1. Current-carrying capacity of grounds
The grounding device shall be of such size as to carry the induced current and anticipated fault current that could flow at the point of grounding for the time necessary to clear the line.
“Note: Refer to ASTM F-855 for specifications for protective grounding equipment.
“B. The connection of the protective ground to the effective ground shall be removed last. Otherwise, electric shock and injury may result.
“Note 1: Electric and magnetic field induction hazards may develop in de-energized conductors, cables and equipment. Hazards due to electric and magnetic field induction may exist when conductors, cables and equipment are parallel or cross other energized circuits.
“Note 2: Refer to IEEE 1048 and IEEE 1246 for additional information for personal protective grounding.”
Subcommittee 8 approved CP 3051 with some additions, including moving the first sentence from 445.B.3 in NESC 2007 to the top of the section. It was agreed by subcommittee members, and rightly so, that proper sequence of installing and removing protective grounds must be followed.
Next, the revision in 445.A was a simple editorial change, and the note under A.1 was added to refer the reader to the ASTM F-855 standard on protective grounding equipment.
Note 1 under 445.B.3 was added to NESC 2012 to caution the reader of the electric and magnetic field induction hazards that can develop when personal protective grounding is used. Note 2 was added to refer the reader to IEEE 1048 and IEEE 1246 for industry-accepted applications of personal protective grounding methods.
Change Proposal Submissions
I submitted both CP 3050 and 3051, which resulted in the minor changes to sections 444 and 445 in NESC 2012. I hope to submit new CPs for the 2017 edition, in which I will recommend adding the changes expected in the next publication of IEEE 1048, currently in its first ballot.
There were hundreds of CPs submitted that recommended changes for NESC 2012. All were reviewed by the eight NESC subcommittees and accepted, accepted with changes or rejected. Anyone can submit a CP recommending a change to the current NESC and I encourage you to do so if you see something you believe should be revised. Preparation for NESC 2017 has begun. The final date to submit CPs is July 15, 2013, less than a year away. In fall 2013 the NESC subcommittees will meet to begin reviewing CPs from the public. The final draft of NESC 2017 will be published in fall 2015, and the final edition will be available August 1, 2016.
About the Author: Brian Erga, CUSP, president of ESCI Inc., has more than 36 years of electric utility expertise and holds a BSEE degree. An expert on safety practices and work methods related to the electric utility industry, he is a member of IEEE/ESMO, NSC, NFPA and ASTM F18, and a member of NESC Subcommittee 8, responsible for NESC Part 4 “Rules for the Operation of Electric Lines.”