Insulator Strengths CP2829

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Insulator Strengths (CP2829)
Bruce Freimark American Electric Power
January 9, 2007 Orlando Towers, Poles
Conductors Meeting
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NESC Rule 277Today and in Past Editions

• Insulators shall withstand all applicable loads
  specified in Rules 250, 251, and 252 except those
  of Rules 250C and 250D without exceeding the
  percentages of their strength rating for the
  respective insulator type shown in Table 277-1.
  Proper allowance should be made for the loads in
  Rules 250C and 250D.
• A Strength Factor is only specified for the
  un-factored, historic, NESC District Loads
  (Heavy. Medium and Light)
• Rules 250C and 250D are Ultimate Loads and Rule
  277 does not specify a strength Factor Proper
  allowance should be made for the loads in Rules
  250C and 250D

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2007 NESC
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Proposals for 2002 NESC

• Major revision to the 2002 NESC proposed a
  complete revision to Strength Loadings,
  deleting district loads and replacing with
  Ultimate Loads (incorporated in 2007 NESC as
  Rules 250C and 250D).
• The 2002 proposal would have applied a strength
  factor of 70 to these Ultimate Loads

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Comments to 2002 Proposal

• In a formal comment to the 2002 CP, ANSI-C29
  Committee (Insulators) stated
• Any load rating system for insulators that
  allows the service loads to exceed the current
  NESC loading limits is unacceptable to NEMA.
  Loads above these limits, no matter how short in
  duration, introduce a risk to the integrity of
  the insulators, and the possibility of either an
  immediate or delayed line failure.

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CP2829 Submitted for 2007 NESC

• Submitted by a Working Group of NESC SC5 to
  address concerns stated in ANSI C29s comments to
  2002 NESC proposal.
• In October 2003, SC5 voted to reject CP2829 for
  the following reason Major changes to the
  insulators strength should be championed by ANSI
  C29.

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Comments Received on CP2829

• Comments were received from four utilities and
  utility organizations supporting the rejection of
  CP2829.
• No comment was received from the ANSI C29
  Committee or NEMA.

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Final Status of CP2829

• In the Fall of 2005, NESC SC5 voted to reconfirm
  the rejection of CP2829.
• NESC Working Group 5.6 was established by NESC
  SC5 to work with ANSI C29 to resolve issues
  relating to Insulator Loading.

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Proposals for 2012 NESC

• September 7 conference call between members of
  NESC SC5, the insulator manufacturers and a few
  additional members of the ANS C29 committee
• It was decided that ANSI C29 would be submitting
  a Change Proposal for the 2012 NESC to change
  NESC Rule 277 in a manner that reflects their
  desired mechanical loading limits.
• Insulator loading (working or ultimate load)
  should not exceed XX percent of insulators
  nameplate rating, with XX being percentages
  similar to those presently printed in the 2007
  NESC.

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Proposals for 2012 NESC

• ANSI C29 has been advised that their Change
  Proposal will need to include technical
  information as to why the proposed changes need
  to be made.