Source: https://www.federalregister.gov/documents/2008/10/22/E8-25079/electric-power-generation-transmission-and-distribution-electrical-protective-equipment-limited
Timestamp: 2018-08-19 00:35:17
Document Index: 419810056

Matched Legal Cases: ['art 1926', '§\u20091926', '§\u20091926', '§\u20091910', '§\u20091910', '§\u20091910', '§\u20091910', 'art 1911']

Federal Register :: Electric Power Generation, Transmission, and Distribution; Electrical Protective Equipment; Limited Reopening of Record
A Proposed Rule by the Occupational Safety and Health Administration on 10/22/2008
Comments must be postmarked no later than November 21, 2008.
https://www.federalregister.gov/d/E8-25079 https://www.federalregister.gov/d/E8-25079
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.
You may submit comments, identified by Docket No. OSHA-S215-2006-0063, by any of the following methods:
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.
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 (§§ 1926.950 through 1926.968), respectively. Proposed § 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 § 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.
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:
○ 3.0 per unit for voltages of 362 kV and less
○ 2.4 per unit for 500 to 550 kV
○ 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.
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.Start Printed Page 62943
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 § 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:
a = A factor relating to the saturation of air at voltages [3] of 345 kV or higher
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 § 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 = 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.
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 § 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.”
Table 1—Comparison of Minimum Approach Distances
Draft IEEE 516 1
Proposed tables R-6 and V-2
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
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.
Table 2—Maximum Transient Overvoltages
System voltage (in kV) Vmax
Maximum anticipated per-unit transient overvoltage pu
Maximum transient overvoltage (in kV)
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 × pu. The maximum overvoltage for phase-to-phase exposures equals Vmax × (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.
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), Start Printed Page 62945Secretary's Order 5-2007 (72 FR 31160), and 29 CFR Part 1911.
1. ANSI is the American National Standards Institute. IEEE is the Institute of Electrical and Electronics Engineers, Inc.
2. EPRI is the Electric Power Research Institute.
3. This voltage is the maximum transient overvoltage.
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).
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.
7. The electrical component of the minimum approach distance is called “minimum tool insulation distance” or MTID in the IEEE draft.
[FR Doc. E8-25079 Filed 10-21-08; 8:45 am]