Fine Print Redux
Continuing the review of the new Fine Print Notes in NFPA 70E.
NFPA Journal®, March/April 2009
As noted in the last column, the new Fine Print Notes (FPNs) in the 2009 edition of NFPA 70E®, Electrical Safety in the Workplace®, are not a part of the standard’s requirements. But they do alert users to concerns of the technical committee or to additional information that will help them apply the standard. FPNs can also be considered when developing site safety programs and doing hazard/risk analysis for work tasks. This column will continue the discussion of new FPNs found in the 2009 edition of NFPA 70E.
Fault clearing time is a major variable in determining the incident-energy level at any location in the power system. FPNs 1 and 2 of Section 130.3, Arc Flash Hazard Analysis, indicate that improper or inadequate maintenance of overcurrent protective devices can increase the incident energy available if the actual clearing times are longer than the expected clearing times. FPN 2 refers to the maintenance section of Chapter 2, and the FPN after Section 210.5, Protective Devices, completes the loop, reminding users that improper maintenance can affect the incident-energy values of the arc flash hazard analysis.
With this information, those analyzing hazards and risks should ask when the protective devices were last calibrated. If the relays have not been tested recently, an alternate work process should be considered, since the available incident energy could be higher than expected. The 2006 edition of NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, contains chapters covering relay, breaker, and fuse information for each different type of electrical equipment. Also, Chapter 21 is devoted to testing and test methods for protective relays. Section 21.10.3, Protective Relays, of NFPA 70B is a good place to start for maintenance recommendations for protective relays.
The FPN after Section 130.5(E), Vehicular and Mechanical Equipment, reminds users that there could be a step potential near the safety ground installed for vehicles if they come in contact with overhead lines. You want to install the safety ground for the operator’s safety, but the FPN reminds people not to stand near that safety ground.
Section 130.7(A), Personal and Other Protective Equipment–General, has several important FPNs. FPN 1 reminds readers that personal protective equipment (PPE) only prevents injury from the burn part of an arc flash, not the explosive effect or the pressure and shrapnel the arc flash generates.
FPN 2 suggests finding alternate work methods when the incident-energy level is above 40 cal/cm2. PPE rated as high as 100 cal/cm2 is available, but this FPN discourages users from working when the incident-energy level is above 40 cal/cm2. There is nothing in NFPA 70E that prohibits wearing PPE rated higher than the incident-energy level, and in some cases, you may want that extra level of protection.
The last three new FPNs we’ll discuss are in Section 130.7(C)(9). I addressed FPN 1 in my July/August 2008 column. FPN 2 reviews the effect of underestimating current and clearing times. FPN 4 reminds you that the current and clearing time must be documented in the energized work permit. Many users of Table 130.7(C)(9) overlook the current and clearing time requirements in the table notes, and FPN 4 reminds them to check the notes and document them in the work permit.
Readers gain significantly more knowledge when they consider the additional information the FPNs provide. The FPNs all contain good subjects to consider when developing individual facility or corporate safety programs and doing the hazard/risk analyses for individual tasks.
I encourage you to also look at the FPNs that are not new to this edition of NFPA 70E, as the information they provide is as important as that contained in the new FPNs. Considering the litigious society we live in, it is important to note these FPNs.
Bill Buss is senior electrical engineer for NFPA and is staff liaison for NFPA 70E.