I suspect that in the past 20 years the utility industry has grounded more circuits for the protection of employees than were ever grounded in the first 115 years of utility operations. Judging from the number of serious incidents and hazardous conditions created by temporarily grounding systems, it seems that we may not have understood all of the issues. It's almost intuitive; grounding makes the work safer, but for whom?
The changes to Section 444.D, “Employee’s protective grounds,” and Section 445.A & B, “Protective grounds,” in the National Electrical Safety Code (NESC) 2012 were approved by NESC Subcommittee 8 after reviewing change proposals (CP) 3050 and 3051, respectively.
In prior iP articles we have discussed effective methods of applying personal protective grounding to both overhead and underground electric utility systems. Proper application of the equipotential grounding method will ensure worker protection during an accidental re-energization or backfeed of the electric utility system. But what does your personal protective grounding practice do to reduce the hazards of induction? Is it possible your personal protective grounding practice is actually increasing the effects of induction? Let’s look at what we call induction, or what electrical engineers refer to as electric field induction and magnetic field induction.
This article is a continuation of the discussion published in the August 2011 issue of Incident Prevention, which covered personal protective grounding of overhead distribution and transmission systems. As with overhead grounding, there are three industry-accepted work methods that allow qualified employees to work with de-energized underground distribution cables and equipment. They are:
• Personal protective grounding, also known as equipotential grounding or EPZ
Personal protective grounding of overhead distribution and transmission lines and equipment is one of three industry-accepted work methods that allow qualified employees to work with de-energized lines and equipment. The other two methods are insulation and isolation. Following are descriptions of all three.
Looking for an alternative to ground-to-ground and cradle-to-cradle? The method suggested here could be your answer.
Georgia Power Company (GPC) has developed the 4 Cover-up Rules philosophy to train employees rather than requiring a ground-to-ground or cradle-to-cradle glove and/or sleeve rule.