Method and device for monitoring severity of vibration in overhead power lines

A method for estimating a severity of vibration, which is a product of vibration frequency f by antinode amplitude of vibration A, and for estimating fatigue lifetime or damage of a suspended electrical cable span of overhead power lines, the suspended electrical cable span having a sag possibly negligible with respect to span length and a local tension, and being subject to a variation of the local tension over time, and to subsequent change of length, due to vibration, the method using an autonomous device with a tension measuring device mounted thereon and fixed to the suspended cable span and an on-board or remotely connected data processing unit, the method comprising steps of:

• a. measuring static H and dynamic ΔH local tension components of the suspended span over a time range as a local tension measurement, with the tension measuring device, so as to obtain a time-dependent tension measurement signal, the antinode amplitude of vibration being related to the local tension measurement;
• and
• b. performing a frequency or time-frequency analysis of the time-dependent tension measurement signal, with the on-board or remotely connected data processing unit,
• wherein an estimation of the severity of vibration is obtained from the local tension components of the formula:
• 1
• π
• ⁢
• Δ
• ⁢
• H
• ⁢
• H
• ES
• ⁢
• m
• =
• Af
• wherein m, E, and S are, respectively, a mass per unit length, a modulus of elasticity, and a section of the suspended electrical cable span, and
• wherein the fatigue lifetime or damage are obtained from a number of cycles estimated from the frequency or time-frequency analysis and a stress level is obtained from the tension.