Research On Monitoring Method For Equivalent Icing Thickness Of Transmission Line Based On Sag

Transmission line icing is a key problem affecting the safe operation of power grid.The existing monitoring methods have partly achieved effective measurement of transmission line icing.However,it still lacks a method to achieve reliable monitoring of transmission line icing in harsh environment.Therefore,the accurate measurement of transmission line’s equivalent icing thickness has great significance in the ice disaster prevention of power grid.Conductor’s sag,which is an obvious variable after icing,can be used to monitor the ice-thickness of conductors remotely.On the basis of the existing sag-temperature icing monitoring method of transmission line,considering the influence of wind load,different icing morphology and icing distribution characteristics on conductor configuration,a computational model of conductor’s equivalent icing thickness under different icing shapes with uniform distribution is established based on sag and temperature.Then this paper analyzes the problems that need to be faced when the model is applied to transmission line icing monitoring.Finally,the transmission line icing monitoring system based on sag and temperature is constructed.To verify the model’s accuracy,a natural icing test of conductor was carried out.The main conclusions are as follows:(1)Under circular icing with uniform distribution,the influence mechanism of ice weight on the configuration of single conductor and bundled conductor is the same.The equivalent icing thickness can be calculated from the center point sag and the surface temperature,combined with the parabolic model and the equation of state.Under special shaped icing,single conductor remains unchanged,while the bundled conductor will twist because of eccentric torque.When the icing shape parameters is known,then the equivalent icing thickness of the special shape icing can be calculated based on circular icing computational model and the constraint relationship of conductor configuration after twisting.(2)This paper analyzes the influence of different modes of tower line connection to the solve process of computation model.Furthermore,the monitoring accuracy requirements and schemes in different span height difference is considered.Moreover,the monitoring schemes under uneven icing distribution is studied.Under icing with uniform distribution,different tower line connection modes will only affect the spatial coordinates of the outgoing line points.Meanwhile,with the increase of span,the requirement of monitoring accuracy for the maximum sag and surface temperature of the conductor decreases gradually.When the span is above 100 m,the temperature measurement needs to achieves ±1℃,and the sag measurement accuracy achieves ±1dm,then the measurement accuracy of equivalent icing thickness growth can achieve1 mm.When the span is less than 100 m,only the temperature measurement accuracy achieves ±0.3℃,and the sag measurement achieves ±1cm,the measurement accuracy of equivalent icing thickness growth can achieve 1mm.For unequal icing distribution transmission line,it is necessary to insert the intermediate measurement point according to the uneven distribution of icing cover and span length.The calculation results of the uneven icing measurement section will appear extreme value,which can be eliminated to increase the accuracy of the calculation result of the entire span.(3)In natural icing experiment,the multi-point measurement fitting result of single and four bundled conductor shows that the test line meet the parabolic configuration.The relative error between the measured values of the midpoint sag and the maximum sag is less than 0.5%.It satisfies the assumption that the midpoint sag approximately equal to the maximum sag of conductor.Under uniform icing distribution,the model of equivalent icing thickness of transmission line based on sag measurement has good accuracy in the calculation of conductor configuration,and the maximum sag relative error is less than1%.Moreover,the computational results equivalent icing thickness and the tension of hanging point both are close to the measured results,and the maximum error is 11.1%.