115 kV Transmission Line — Conductor Sag & Failure Analysis

Recurring failures on a 115 kV regional transmission line called for more than a conventional line-rating check. Working within the operator's regional engineering team at Celsia, Gridradix built a coupled thermal–electromagnetic finite-element model of the line conductor in COMSOL Multiphysics to quantify how current loading, ambient conditions and electromagnetic losses drive conductor temperature and sag — and where the resulting clearances and mechanical stresses explained the failure history. The methodology was written up and submitted for peer review as "Thermal and Electromagnetic Impact on Conductor Sag in a 115 kV Transmission Line: A Finite Element Approach" (CLEI-JCC-CHILECON 2025, Valparaíso, Chile).

1. 01

   Root-cause analysis of 115 kV transmission-line failures using finite-element modelling in COMSOL Multiphysics.

2. 02

   Coupled electromagnetic–thermal simulation of the phase conductor, linking Joule and proximity losses to the conductor temperature field under realistic loading and ambient conditions.

3. 03

   Evaluation of conductor sag and ground clearance as a function of thermal state, and of the mechanical stresses at attachment points.

4. 04

   Correlation of simulated hot-spot and sag behaviour with the observed failure locations and events.

5. 05

   Standards-based lightning performance assessment of the line — shielding-failure and back-flashover rates per IEEE Std 1243 — computed with in-house MATLAB tooling.

6. 06

   Documentation of the method and findings for publication and for the operator's asset-management decisions.

The work replaced rule-of-thumb line ratings with a physics-based picture of how the conductor actually heats, sags and fails in service — giving the operator a defensible basis for loading limits and reinforcement, and producing a methodology, submitted for peer review, that can be reused on other lines.

• Insulation coordination All cases — Insulation coordination →

Systems & technologies

• 115 kV line
• COMSOL Multiphysics
• Thermal–EM coupling
• Conductor sag
• IEEE Std 1243
• MATLAB
• Root-cause analysis

Notes

Methodology submitted as: Thermal and Electromagnetic Impact on Conductor Sag in a 115 kV Transmission Line: A Finite Element Approach — CLEI-JCC-CHILECON 2025, Valparaíso.

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