Jean-Louis Lilien

Galloping of electrical lines in wind tunnel facilities

Abstract Galloping is a large amplitude, low frequency, wind-induced oscillation of overhead electrical lines. In the vast majority of cases, an ice accretion is present on the conductor: this has the effect of modifying the conductors cross-sectional shape such that it becomes aerodynamically and/or aeroelastically unstable. This paper deals with galloping generated during wind tunnel testing. A typical eccentric ice shape has been reproduced on a classical stranded overhead line conductor. In the first part, the quasi-static aerodynamic coefficients have been measured for different wind speeds in the range of galloping observations. In the second part the same sample has been suspended in the wind tunnel by springs in order to obtain a system as close as possible to an overhead line (vertical, horizontal and rotational movements are allowed). For appropriate angles of attack, galloping has been obtained. For an electrical engineer, there are two kinds of galloping: Den-Hartog galloping and flutter galloping. The first one is an aerodynamic instability because the main factor at the origin of this problem is the aerodynamic properties of the ice deposit. The flutter galloping is an aeroelastic problem. For this type of instability, the structural properties of the line are also important and there is a coupling between at least two degrees of freedom. Both of them were recorded. These tests make available a full set of data and recordings of limit cycles during galloping events. Such measurements can be used for numerical model validation and for efficiency evaluation of some anti-galloping means (detuning, increase of damping in vertical, torsion, modification of rotational inertia, etc.).

Overhead electrical transmission line galloping. A full multi-span 3-DOF model, some applications and design recommendations

A full multi-span three-degree-of-freedom (3-DOF) iced power transmission line model is presented. This new model is applicable for describing the galloping phenomena of both single and bundle lines, for performing static and dynamic analysis, and predicting the galloping behavior of iced power transmission lines, as well as for performing checks against field experience. Some applications for overhead power transmission lines design are detailed. Some original recommendations for the design of multi-span bundle configurations are also proposed.

Benchmark cases for galloping with results obtained from wind tunnel facilities validation of a finite element model

The full set of data of recent galloping results obtained from wind tunnel facilities are presented. These results allow to define benchmark cases for the validation of any numerical model of galloping. This validation is realized in this paper with a finite element model.

A new damper to solve galloping on bundled lines. Theoretical background, laboratory and field results

A new kind of anti-galloping device for bundled lines is presented. The approach is complete, including basic mechanisms, laboratory results, valuation of the efficiency on a whole line and field results. The device is the torsional damper and detuner. The high voltage and dynamic behaviour are discussed.

Uprating Transmission Lines through the use of an innovative real-time monitoring system

This paper describes a brand new method of real-time monitoring of overhead transmission lines. The method makes use of what is called the “Ampacimon” system. The system uses an Ampacimon module, which is a real time monitoring device that deduces the sag by vibration analysis without the need for any line data or environmental data. The Ampacimon system has been proven to be accurate within a sag error margin of ±2%.

Dynamic prediction of energy delivery capacity of power networks: Unlocking the value of real-time measurements

The paper focuses on advances in short-term prediction (1-4 Hours) of dynamic line rating as an example of what can be achieved by the combination of advanced network sensors and the latest machine learning, data-mining tools. Combining these tools has allowed us to achieve reliable and usable predictions that allow the network operators to switch from a static approach to a manageable dynamic one that significantly increases asset utilisation without reducing security of supply.

A new theory for torsional stiffness of multi-span bundle overhead transmission lines

A new theory for the torsional stiffness of multi-span bundle overhead power transmission lines is presented. The torsional mechanism is clarified. A simplified torsional stiffness formula is obtained which allows for the complex bundle stiffness to be directly calculated from the basic parameters. Applications in the choices of yoke plates and suspension clamps are detailed. The new theory correlates with experiments to a high degree of accuracy.

Aeolian Vibrations on Power-Line Conductors, Evaluation of Actual Self Damping

Aeolian vibrations of power lines are induced by Von Karman vortex shedding. Without dampers, the amplitude of vibration very much depends on conductor self damping, which may be very low. The purpose of this paper is to show measurements of these vibrations carried out by a new experimental device which is able to perform continuous measurements in the full range of frequencies and amplitudes. In this paper, 550 h of continuous recording on four different conductors placed in similar conditions is detailed. An evaluation of self damping power, based on observations, is proposed.

Calculation of spacer compression for bundle lines under short-circuit

In a recent Institute paper, the authors presented experimental results on spacer compression, which showed clearly, that the simplified analytical calculation method used today, the so called Manuzio formula, leads to severe underestimation of spacer compression and thus to faulty spacer design. In this paper, further test results are presented covering todays practical range of bundle configurations, subspan lengths, sagging tensions and short-circuit levels for transmission lines. Based on these results, the authors present a new calculation method for spacer compression, which builds up on well accepted IEC standards.

Spacer compression for a triple conductor bundle

This paper presents investigations on spacer compression. It contains results of short-circuit tests on suitable instrumented spacers, comparison with advanced calculation methods and a critical review of current practice for spacer design. The main conclusion of the paper is, that in certain cases caution is needed, when designing spacers on compression by using the simple Manuzio formula available today.