[Federal Register: October 22, 2008 (Volume 73, Number 205)]
[Proposed Rules]
[Page 62942-62945]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr22oc08-25]
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DEPARTMENT OF LABOR
Occupational Safety and Health Administration
29 CFR Parts 1910 and 1926
[Docket OSHA-S215-2006-0063]
RIN 1218-AB67
Electric Power Generation, Transmission, and Distribution;
Electrical Protective Equipment; Limited Reopening of Record
AGENCY: Occupational Safety and Health Administration (OSHA), U.S.
Department of Labor.
ACTION: Notice of limited reopening of rulemaking record.
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SUMMARY: On June 15, 2005, OSHA published a proposed rule to revise the
general industry and construction standards for electric power
generation, transmission, and distribution work and for electrical
protective equipment. Public comments were received, a hearing was
held, and the final posthearing briefs were due on July 14, 2006.
The proposed general industry and construction standards for
electric power generation, transmission, and distribution work included
revised minimum approach distance tables. Those tables limit how close
an employee (or a conductive object he or she is contacting) may get to
an energized circuit part. After the rulemaking record on the proposal
closed, the technical committee responsible for developing the tables
in the consensus standards on which the proposal was based discovered
what in their view was an error in their calculation of minimum
approach distances for certain voltages.
OSHA is reopening the record on this proposal to obtain comments
related to the affected minimum approach distances. The record will
remain open on this limited basis for 30 days.
DATES: Comments must be postmarked no later than November 21, 2008.
ADDRESSES: You may submit comments, identified by Docket No. OSHA-S215-
2006-0063, by any of the following methods:
Federal eRulemaking Portal: http://www.regulations.gov.
Follow the instructions for submitting comments.
Fax: If your comments, including attachments, do not
exceed 10 pages, you may fax them to the OSHA Docket Office at (202)
693-1648.
Mail, hand delivery, express mail, messenger, or courier
service: You must submit two copies of your comments and attachments to
the OSHA Docket Office, Docket No. OSHA-S215-2006-0063, U.S. Department
of Labor, Room N-2625, 200 Constitution Avenue, NW., Washington, DC
20210; telephone (202) 693-2350 (OSHA's TTY number is (877) 889-5627).
Deliveries (hand, express mail, messenger, and courier service) are
accepted during the Department of Labor's and Docket Office's normal
business hours, 8:15 a.m.-4:45 p.m., e.s.t.
Instructions: All submissions must include the agency name and the
docket number (Docket No. OSHA-S215-2006-0063) or Regulatory
Information Number (RIN 1218-AB67) for this rulemaking. All comments
received will be posted without change to http://dockets.osha.gov,
including any personal information provided.
Docket: To read or download comments and materials submitted in
response to this Federal Register notice, go to Docket OSHA-S215-2006-
0063 at http://www.regulations.gov or at the OSHA Docket Office at the
previously listed address. All comments and submissions are listed in
the http://www.regulations.gov index. However, some information (for
example, copyrighted material) is not publicly available to read or
download through that Web page. All comments and submissions, including
copyrighted material, are available for inspection and copying at the
OSHA Docket Office.
Electronic copies of this Federal Register document are available
at http://www.regulations.gov. This document, as well as news releases
and other relevant information, also are available at OSHA's Web page
at http://www.osha.gov.
FOR FURTHER INFORMATION CONTACT: General information and press
inquiries: Contact Ms. Jennifer Ashley, Office of Communications, Room
N-3647, OSHA, U.S. Department of Labor, 200 Constitution Avenue, NW.,
Washington, DC 20210; telephone (202) 693-1999.
SUPPLEMENTARY INFORMATION: On June 15, 2005, OSHA issued a proposed
rule to revise the general industry and construction standards for
electric power generation, transmission, and distribution work and for
electrical protective equipment (70 FR 34822). The Agency solicited
public comments and held a public hearing on March 6 through 14, 2006.
Administrative Law Judge William Colwell set a deadline of July 14,
2006, for the filing of written comments, summations, position
statements, and briefs.
The proposed requirements for electric power generation,
transmission, and distribution work for general industry and
construction would be contained in 29 CFR 1910.269 and 29 CFR part
1926, subpart V (Sec. Sec. 1926.950 through 1926.968), respectively.
Proposed Sec. 1926.960(c)(1) would require employees to maintain
minimum approach distances from exposed energized parts. The minimum
approach distances are specified in proposed Tables V-2 through V-6.
Existing Sec. 1910.269(l)(2) and proposed Tables R-6 through R-10
contain equivalent requirements for general industry.
OSHA developed the minimum approach distance tables in the proposal
using the following principles (see 70 FR 34862):
ANSI/IEEE \1\ Standard 516-1987 was to be the electrical
basis for approach distances: Table 4 (Alternating Current) and Table 5
(Direct Current) for voltages above 72.5 kV. Lower voltages were to be
based on ANSI/IEEE Standard 4. The application of ANSI/IEEE Standard
516-1987 was inclusive of the formula used by that standard to derive
electrical clearance distances.
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\1\ ANSI is the American National Standards Institute. IEEE is
the Institute of Electrical and Electronics Engineers, Inc.
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Altitude correction factors were to be in accordance with
ANSI/IEEE Standard 516-1987, Table 1.
The maximum design transient overvoltage data to be used
in the development of the basic approach distance tables were:
[cir] 3.0 per unit for voltages of 362 kV and less
[cir] 2.4 per unit for 500 to 550 kV
[cir] 2.0 per unit for 765 to 800 kV
All phase-to-phase values were to be calculated from the
EPRI \2\ Transmission Line Reference Book for 115 to 138 kV.
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\2\ EPRI is the Electric Power Research Institute.
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An inadvertent movement factor (ergonomic component)
intended to account for errors in judging the approach distance was to
be added to all basic electrical approach distances (electrical
component) for all voltage ranges. A distance of 0.31 meters (1 foot)
was to be added to all voltage ranges. An additional 0.3 meters (1
foot) was to be added to voltage ranges below 72.6 kV.
The voltage reduction allowance for controlled maximum
transient overvoltage was to be such that the minimum allowable
approach distance was not less than the given approach distance
specified for the highest voltage of the given range.
The transient overvoltage tables were to be applied only
at voltage ranges inclusive of 72.6 kV to 800 kV. All tables were to be
established using the higher voltage of each separate voltage range.
As noted in Appendix B to existing Sec. 1910.269 and in Appendix B
to proposed subpart V, the following equation is used to calculate the
electrical component of the minimum approach distance for voltages of
72.6 kV to 800 kV:
D=(C+a)xpuxVmax Equation (1)
Where:
D = Electrical component of the minimum approach distance in air in
feet
C = 0.01 to take care of correction factors associated with the
variation of gap sparkover with voltage
a = A factor relating to the saturation of air at voltages \3\ of
345 kV or higher
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\3\ This voltage is the maximum transient overvoltage.
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pu = Maximum anticipated transient overvoltage, in per unit (p.u.)
Vmax = Maximum rms system line-to-ground voltage in kilovolts--it
should be the "actual" maximum, or the normal highest voltage for
the range (for example, 10 percent above the nominal voltage).
Source: Formula developed from ANSI/ IEEE Standard No. 516-1987.
For phase-to-phase exposures, the maximum phase-to-phase transient
overvoltage must be used to calculate minimum approach distances from
one phase to another. As noted in Appendix B to existing Sec. 1910.269
and in Appendix B to proposed subpart V, the following equation is used
in determining the phase-to-phase maximum transient overvoltage based
on the per unit of the system nominal voltage phase-to-ground crest:
pup=pug+1.6 Equation (2)
Where:
pup = p.u. phase-to-phase maximum transient overvoltage
pug = p.u. phase-to-ground maximum transient overvoltage.
This value was to be used in Equation (1) to calculate the phase-
to-phase minimum approach distance (MAD).
The technical committees responsible for ANSI/IEEE and the National
Electrical Safety Code (NESC, ANSI C2) calculated minimum approach
distances based on these equations. Because OSHA intended to use the
same methodology, it relied on the technical committees' calculations
as they appeared in the two consensus standards and carried those
distances into the proposed standard.
During the most recent revision cycle for ANSI/IEEE Standard 516,
the IEEE technical committee responsible for revising that standard
identified what in their view was an error in the calculations of
phase-to-phase minimum approach distances for nominal voltages 230 kV
and higher. At these voltages, the saturation factor, a, which appears
in Equation (1), varies depending upon the voltage. The value of a
increases with increasing voltage. The NESC subcommittee originally
calculated the phase-to-phase minimum approach distances using a value
for the saturation factor, a, corresponding to the phase-to-ground
maximum transient overvoltage rather than the maximum phase-to-phase
transient overvoltage.\4\ Because the MADs used in OSHA's 2005 proposal
were taken from the consensus standard, OSHA wants to obtain comments
on whether changes are necessary to the tables as proposed.
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\4\ ANSI/IEEE Standard 516-1987 did not contain distances for
phase-to-phase exposures. The NESC subcommittee derived them by
applying the IEEE equation to the phase-to-phase temporary
overvoltages calculated using Equation (2).
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The IEEE committee proposed a correction in a draft revised IEEE
Standard 516 (Draft 9).\5\ Table 1 shows the difference
between the minimum approach distances in that draft IEEE Standard 516
and those contained in proposed Sec. 1910.269 Table R-6 and proposed
Subpart V Table V-2 for voltages over 72.5 kV. A subsequent draft from
the IEEE committee (Draft 10) dropped values for voltages with
temporary overvoltages exceeding 1600 kV.\6\ Draft 10 leaves
the determination of these values to "good engineering judgment."
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\5\ This document is available for inspection and copying in the
Docket Office at the address listed in the ADDRESSES section of this
notice.
\6\ This document is also available for inspection and copying
in the Docket Office at the address listed in the ADDRESSES section
of this notice.
Table 1--Comparison of Minimum Approach Distances
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Distance (m)
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Phase-to-ground exposure Phase-to-phase exposure
Nominal voltage in kilovolts phase-to-phase -------------------------------------------------------------------
Proposed Proposed
Draft IEEE 516 tables R-6 and Draft IEEE 516 tables R-6 and
\1\ V-2 \1\ V-2
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72.6 to 121................................. 1.01 0.95 1.36 1.29
138 to 145.................................. 1.15 1.09 1.57 1.50
161 to 169.................................. 1.29 1.22 1.85 1.71
230 to 242.................................. 1.71 1.59 2.91 2.27
345 to 362.................................. 2.72 2.59 5.13 3.80
500 to 550.................................. 3.54 3.42 6.89 5.50
765 to 800.................................. 4.64 4.53 9.35 7.91
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\1\ Draft 9 of IEEE Standard 516 provides separate minimum approach distances for exposures with and
without tools in the air gap. The distances in the table are for tools in the air gap (called "minimum tool
insulation distances" in the IEEE standard.). The NESC minimum approach distances tables are derived from the
distances in IEEE Standard 516 corresponding to exposures with tools in the air gap.
As can be seen from Table 1, the IEEE's proposed approach from
Draft 9 results in a substantial increase in MAD for phase-to-
phase exposures at voltages of 230 kV and higher.
For purposes of the public's consideration of the issues in this
reopening notice, OSHA points out the following technical issues:
1. For voltages over 72.5 kV, the electrical component of the
minimum approach distances \7\ in OSHA's proposal is based on testing
of rod-to-rod gaps performed by 13 laboratories. This testing extends
to approximately 1.6 MV. This voltage is sufficient to cover the
maximum transient overvoltage for all phase-to-ground exposures.
However, it does not extend to the maximum transient overvoltages for
phase-to-phase exposures of voltages 362 kV and higher, as shown in
Table 2.
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\7\ The electrical component of the minimum approach distance is
called "minimum tool insulation distance" or MTID in the IEEE
draft.
Table 2--Maximum Transient Overvoltages
------------------------------------------------------------------------
Maximum transient overvoltage (in
Maximum kV)
System voltage anticipated per- -----------------------------------
(in kV) Vmax unit transient Phase-to-ground Phase-to-phase
overvoltage pu exposure exposure
------------------------------------------------------------------------
362 3.0 1086 1665
552 2.4 1325 2208
800 2.0 2208 2880
------------------------------------------------------------------------
Note: The maximum transient overvoltage for phase-to-ground exposure
equals Vmax x pu. The maximum overvoltage for phase-to-phase exposures
equals Vmax x (pu + 1.6).
In Draft 9, the IEEE committee addressed this issue by
extending the equations used for calculating the minimum air insulation
distance beyond the highest voltage covered by the test data. Other
approaches using the same criteria upon which the minimum approach
distances are based could include: (1) Using available test data for
conductor-to-conductor gaps and converting them to equivalent rod-to-
rod values, and (2) commissioning further tests.
2. IEEE Drafts 9 and 10 also include other
refinements of the method used to calculate minimum approach distances
intended to make the calculations more precise and repeatable. For
example, the saturation factor is now based on equations resulting from
curve fitting the test data rather than from reading the value directly
from a graph of these data.
3. If the minimum approach distances are based on the minimum tool
insulation distance, as is done in the NESC, there would be additional
slight increases in MAD for all voltages of 72.6 kV and higher with
both phase-to-ground and phase-to-phase exposures.
In light of the IEEE committee's draft revisions, OSHA is reopening
the record on the electric power generation, transmission, and
distribution standard to invite comments, evidence, and data on the
limited question of whether the Agency should adopt minimum approach
distances different from those proposed for voltages of 72.6 kV and
higher. The Agency strives to adopt a final rule that is based on sound
and up-to-date engineering, and scientific principles and is
specifically inviting comments on the following questions:
1. Should OSHA adopt MADs that are different from those proposed
for voltages of 72.6 kV and higher and, if so, should it adopt the
distances in Draft 9 or 10 of IEEE Standard 516?
2. Are there methods other than those in Drafts 9 and
10 of IEEE Standard 516 that would be more appropriate in the
calculation of MAD for maximum transient overvoltages beyond existing
data for rod-to-rod gaps?
3. Should MAD for voltages of 72.6 kV and higher be based on the
minimum tool insulation distance as is the case in the 2007 NESC?
4. Should the final rule include separate minimum approach distance
tables for air gaps and for tools as is done in Drafts 9 and
10 of IEEE Standard 516?
OSHA is reopening the record solely on issues related to minimum
approach distances for voltages of 72.6 kV and higher. The record is
not being reopened on any other issue.
List of Subjects in 29 CFR Parts 1910 and 1926
Electric power, Fire prevention, Hazardous substances, Occupational
safety and health, Safety.
Authority and Signature
This document was prepared under the direction of Edwin G. Foulke,
Jr., Assistant Secretary of Labor for Occupational Safety and Health,
U.S. Department of Labor, 200 Constitution Avenue, NW., Washington, DC
20210. It is issued pursuant to sections 4, 6, and 8 of the
Occupational Safety and Health Act of 1970 (29 U.S.C. 653, 655, 657),
Secretary's Order 5-2007 (72 FR 31160), and 29 CFR Part 1911.
Signed at Washington, DC, this 16th day of October 2008.
Edwin G. Foulke, Jr.
Assistant Secretary of Labor for Occupational Safety and Health.
[FR Doc. E8-25079 Filed 10-21-08; 8:45 am]
BILLING CODE 4510-26-P
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