Purpose

Pursuant to Alberta Utilities Commission Rule 017, Procedures and Process for Development of ISO Rules and Filing of ISO Rules with the Alberta Utilities Commission (AUC Rule 017), the AESO is providing notice and seeking feedback from stakeholders on the development of proposed amendments to Section 503.22 of the ISO rules, Bulk Transmission Line Technical Requirements and Section 503.1 of the ISO rules, Functional Specification & Legacy Treatment. For additional information, please see the Feb. 26, 2025 Letter of Notice.

Request for Feedback

The AESO is requesting feedback on the development of proposed amendments to Section 503.22 and Section 503.1 by March 27, 2025. All responses will be shared in their original format on AESO Engage. In accordance with AUC Rule 017, the AESO will provide written responses to the survey responses and post these responses on AESO Engage.

Written Consultation Materials

Can be found in the AESO Materials section.

Instructions 

Survey Questions

1. Do you agree that voltage levels can remain as the primary driver for determining the return periods for weather loading?
2. Do you agree that other factors such as circuit length, generation/load type, cost of failure, etc. could be used in determining the return periods for weather loading?
3. Do you agree that further clarifications could be provided regarding the “other factors” in terms of circuit length thresholds, definition of critical loads, consequence of failure, etc.? Do you agree that these clarifications could be provided in ID #2010-005R?
4. Do you agree that the 50, 75, and 100 years return periods for bulk transmission line design should remain unchanged?
5. Do you agree that the gust wind maps and snow & ice loading map found on the AESO Engage page should be used for bulk transmission line design?
6. Do you agree that ACSR and ACSR/TW conductor should remain as the default conductor type for bulk transmission line design?
7. Do you agree that ACSS conductor should be an acceptable conductor type, provided that an acceptable sparing strategy is submitted by the line owner?
8. If ACSS conductor is used, do you agree with the following safety margin parameters for ACSS conductor:
   • the conductor strength is such that its tensions under AEUC loadings do not exceed 60% of its rated tensile strength; and
   • the tension under the maximum reliability-based design, including those involving high wind, combined wet snow and wind, or in-cloud icing, does not exceed 90% of the rated tensile strength of the conductor.
     If not, what parameters do you propose?
9. Do you agree that some 240/260 kV bulk transmission lines could be designed with a maximum conductor temperature of <100°C, such as radially connected lines or tapped lines where there is low probability of other taps in the future?
10. Do you agree a cost comparison study of using 100°C versus <100°C for such 240/260 kV bulk transmission lines should be required?
11. Do you agree that 138/144 kV bulk transmission lines should be allowed on road allowance?
12. Do you agree that the placement of 240/260 kV bulk transmission lines on road allowance should continue to be assessed on a case-by-case basis?
13. Do you agree the minimum easement width on private property for single-pole transmission lines should be 6 meters for 138/144 kV lines and 7 meters for certain 240/260 kV lines, if the lines are placed adjacent to road allowance? If not, what parameters do you propose?
14. Do you agree that Section 503.22 should specify which party should be responsible for the purchase of the permanent or temporary easement for live-line maintenance and vegetation management purposes? If so, who should be responsible?
15. Do you agree that the free-fall requirements and the use of voltage level as the criterion should remain unchanged?
16. Do you agree that IEEE Standard 738 should remain the standard for the determination of static thermal ratings of bulk transmission lines?
17. Do you agree that the following environmental parameter values should remain unchanged for the calculation of thermal static ratings of lines with ACSR conductors:
    • Absorptivity = 0.8
    • Emissivity = 0.6
    • Maximum conductor temperature = 100°C
      If not, what values do you propose?
18. Do you agree that the following environmental parameter values should be used for the calculation of thermal static ratings of lines with ACSS conductors:
    • Absorptivity = 0.8
    • Emissivity = 0.6
    • Maximum conductor temperature = As per the conductor manufacturer’s technical data report
      If not, what values do you propose?
19. Do you agree that subsection 20 should be removed from Section 503.22 because FAC-008 has provisions for emergency thermal ratings?
20. Given your organization’s maintenance policy, methods, and tools, how do you interpret the phrase “reasonably anticipated maintenance methods and requirements” and the “otherwise” in the language of subsection 23? Do you agree that clarifications regarding these phrases could be provided in ID #2010-005R? What clarifications could be provided?
21. Do you agree that further guidance could be provided for MPC line designers to ensure live-line maintenance is incorporated in the design to reasonably meet the incumbent TFO’s requirements? Do you agree that these clarifications could be provided in ID #2010-005R? What clarifications could be provided?
22. Do you agree that the applicability criteria in subsection 5 of Section 503.1 should be either 1.5 km or 5% of circuit length, whichever is larger? If not, what parameters do you propose?
23. Do you agree that the minimum requirement should remain unchanged for 3/8” Gr. 220 galvanized steel strand for OHSW for a bulk transmission line with >150 m average span length?
24. Do you agree that the existing requirements in subsection 15 of Section 503.22 should remain unchanged?
25. Do you agree that the galloping map found on the AESO Engage page should be used for bulk transmission line design (i.e. bulk transmission lines in the galloping zones should be designed to meet conductor galloping requirements)?
26. Do you agree that interphase spacers should remain as the preferred method for galloping mitigation for compact line design or when using existing towers where the galloping envelope design and clearances cannot be met?
27. Do you agree that the Charpy test requirements for non-load bearing ferrous components should be relaxed?
28. In your opinion, what hardware components should be classified as non-load bearing ferrous hardware components? Do you agree that further clarification could be provided in ID #2010-005R regarding non-load bearing ferrous hardware components?
29. Do you agree that ASTM A370 should be the standard for measuring the tensile strength of metals?
30. Do you agree that line owners should be allowed to include additional extraordinary risk factors, such as wildfire risk and flooding concerns in a line optimization study? Do you agree that further clarification could be provided in ID #2010-005R about how these extraordinary risk factors should be modeled in the line optimization study?