R.24-10-005: Proposed Changes to General Order 95’s Design Methodology for Load and Resistance Factor Design

Order Instituting Rulemaking to Consider Proposed Changes to General Order 95 to Modernize the Rules and Regulations Governing the Design and Construction of Overhead Electric and Communications Facilities in California.

Background

On March 18, 2024, Southern California Edison Company (SCE or Petitioner) filed a petition, on behalf of the General Order 95/128 Rules Committee, to consider proposed changes to the Commission’s General Order 95 (GO 95) to modernize the rules and regulations governing the design and construction of overhead electric and communications facilities in California.

The petition requested that the Commission consider modernizing GO 95 to update the rules and regulations governing the design and construction of overhead electric and communications facilities in California through the incorporation of Load and Resistance Factor Design (LRFD). In its petition, SCE stated that LRFD is an engineering methodology adopted and applied through the United States and North America. Also in its petition, SCE included a package of 21 proposed rule changes designed to incorporate LRFD into GO 95. SCE stated that the proposed rule changes aim to improve fire-safety, public and worker safety, as well as electric and communications systems reliability. Since the initial petition, SCE submitted additional proposed rule changes as part of its reply comments on the Order Instituting Rulemaking (OIR).

The current methodology in GO 95, Working Stress Design, uses a single safety factor to design overhead lines. Changing the methodology to LRFD would split the safety factor into two components: (1) the load factor to account for variability in loads and (2) the strength factor to account for variability in strengths of materials. The petition stated the proposed load and strength factor values were chosen to yield equivalent results as applying the current safety factor values.

An OIR was issued on October 23, 2024. The subsequent Assigned Commissioner’s Scoping Memo and Ruling (scoping memo) raised the following issues for consideration:

Whether the Commission should revise GO 95 to replace the Working Stress Design methodology with the LRFD methodology.
If the LRFD methodology is adopted, what related revisions in GO 95 should be made to incorporate LRFD methodology for seamless use? This may include defining load factors and strength factors to replace the existing safety factors associated with the Working Stress Design methodology.
Should the Commission create a process, including a framework, testing, or other means, to assess the safety impacts of the LRFD Load and Strength Factors? This may include a statistical framework to compare in-field performance against theoretical, statistically targeted, safety performance of the Load and Strength Factors.

The scoping memo required a series of workshops to discuss scoped issues, which were summarized in a workshop report. Details of the workshops are summarized in Public Engagement Section below.

Relevant Documents

These documents are identified as either key CPUC-issued documents, proposed rule changes, or explanations of the proposal. The posting of party-filed documents is not an endorsement of the documents, but rather an attempt to help stakeholders understand the proposal. Review the Proceeding Details for a full list of all relevant documents.

Current Edition of GO 95: Rules for Overhead Electric Line Construction
Historical Information for GO 95
Petition: Petition of Southern California Edison Company (U 338-E) on Behalf Of the GO 95/128 Rules Committee to Adopt New General Order 95 Rules for Supply and Communication Lines
OIR: Order Instituting Rulemaking to Consider Proposed Changes to General Order 95 to Modernize the Rules and Regulations Governing the Design and Construction of Overhead Electric and Communications Facilities in California
Additional proposed rule changes submitted in SCE’s reply comments: Southern California Edison Company’s (U 338-E) Reply Comments On Order Instituting Rulemaking To Consider Proposed Changes To General Order 95
IOU Led Party Workshop Report (pre-scoping memo): Southern California Edison Company’s (U 338-E), Pacific Gas And Electric Company’s (U 39-E), And San Diego Gas & Electric Company’s (U 902-E) Joint Workshop Report
Assigned Commissioner’s Scoping Memo and Ruling
Workshop 1 Presentation on the Proposed Changes by GO 95 Working Group: LRFD presentation for May 2025 workshop 5-29-25
Workshop Protocols: R.24-10-005 Workshop Protocols for GO 95 Proposed Rule Changes
ALJ Ruling on Workshop Report and Supplemental Questions with Attachments