Predicting Vibration Fatigue for Overhead Line Conductor Systems
National Grid Electricity Transmission
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Network Innovation Allowance
ET - Network improvements and system operability
Asset Management, Condition Monitoring, Conductors, Overhead Lines and Electricity Transmission Networks
Conductor vibrations are one of the most common reasons for conductor fatigue and failures. CIGRE has highlighted that for ACSR (Aluminum Conductor Steel Reinforced) there is uncertainty in relation to self-damping since it depends on the tension shared between aluminum strands and the core at different temperatures. This uncertainty is even more prominent with High Temperature Low Sag (HTLS) conductors. Furthermore, the current methods for quantifying vibration fatigue are based on beam theory (which is valid only for homogeneous conductors) which ignores the properties of the interlayers (e.g., trapezoidal vs. round strands). Past work indicated that the natural frequency under the assumption of the conductor with isotropic properties (i.e. solid homogeneous beam) results in more than 40% error on vibration effects when compared to the composite (sandwich beams) conductor assumption.
Currently, there is no existing method to calculate the fatigue of composite (bimetallic, bi-material) conductors and there is also a lack of metrics (apart bending stress) that can be associated with the effect of vibrations on conductor and conductor bundles condition (life expectancy and fatigue).
As a result, there are high levels of uncertainty in the expected life of these assets. Better understanding vibration fatigue will allow for more accurate assessment of life expectancy.
To demonstrate that conductor structure and stranding geometry affect vibration fatigue (for conductors and bundles) and develop a preliminary computational tool to quantify it.
To identify the properties that make some conductors more immune to vibrations and correlate these with any benefits on increasing overhead line systems’ power flows.