Research On Dynamic Characteristics Of Transmission Line After Ice-shedding And Fbg Detection Technology

The ice dropped off from the ice-conductor uniformly or non-uniformly under particular temperature,and wind conditions or shocks.It is of great significance to study the dynamic characteristics of displacement and tension and study the measurement method of the dynamic force of transmission lines for their structural and insulation design and operation status evaluation.Firstly,an isolated span conductor was built,and the ice-conductor was simulated through lumped load method.Ice-shedding tests were carried out under different ice-shedding modes,sag-to-span ratio(SSR),and ice thickness.The displacement and dynamic tension acquisition module were used to obtain the dynamic response of the conductor.The experimental results show that the greater the ice thickness,the faster the energy dissipates after ice-shedding,and the stronger the jumping ability.Under the same ice condition,the energy of the large SSR lead dissipates quickly after ice-shedding,and the conductor jump ability is weak.And when the SSR is large,the tension attenuation curve is irregular,the occurrence time of the maximum tension is not in the first cycle,there are three vibration half-waves,and two peaks of tension appear in each cycle,indicating that the vibration shape of the conductor affects the tension.When partial ice-shedding occur,the closer the ice-shedding position is to the middle of the span,the larger the amplitude of the dynamic tension fluctuation and the smaller the static tension.During 1/2 ice-shedding,the shedding conductor jumps up instead of the non-shedding conductor lead reversely jumping,forming an irregular dynamic tension waveform,which can cause flashover accidents in severe cases.Secondly,fiber bragg grating composite insulators was proposed to measure the dynamic load of the transmission line during ice-shedding.A fiber bragg grating composite insulator core rod was fabricated,and the linear relationship between the change in the center wavelength of the fiber bragg grating sensor and the stress and temperature was analyzed.A temperaturestrain cross-sensitivity solution was proposed.The finite element method was used to analyze the strain transfer model of the fiber bragg grating composite insulator.The results show that the average strain transfer rate of the two-point paste method is higher than that of the full paste method.The width of the paste layer,the paste length,and the elastic modulus of the paste layer should be increased and thickness of the intermediate layer should be reduced.Finally,a calibration test and a ice-shedding test were carried out.The change of vertical and horizontal force of the transmission conductor during the ice-shedding was measured using fiber grating composite insulator core rod,and the center wavelength was converted into stress value and the resistive tension sensors was used for comparison.The test results show that: the fiber bragg grating composite insulator core rod can realize the dynamic load of the conductor after ice-shedding.It is affected by the increase of the axial force applied to the core rod,the paste parameters and so on.When FBG was used to measure horizontal tension,its effective vibration signal length is longer than that of vertical load.The FBG with a small intermediate layer can effectively attenuate the vibration signal for 12 vibration periods,and the difference between the peak value and the valley value can be less than 30% compared with the tension sensor.