Research On The Indirect Monitoring Technique Of Ice Accretion For OPGW

Optical Fiber Composite Overhead Ground Wire(OPGW) is an important part of power system because of its good abilities of lightning protection and communication. Owing to its importance to the normal operation of grids, it will cause serious damage to power system, if OPGW is broken down by the ice accretion on its suface. At present, most of the monitor systems for ice accretion mounted in the grids are designed for conductors,, while monitoring the ice accretion on OPGWs is not under cover and the monitor systems for OPGWs are rarely considered and discussed. The environmental parameters of icing process of OPGWs and conductors are basically identical, for they stay in the same environment, so the icing process of OPGWs and conductors are correlated. The main objective of this thesis is to devise an approach to estimate the difference of ice thickness between the OPGW and the conductor by the use of the data acquired from the power system. In this way, the ice thickness of OPGWs can be indirectly watched by the monitoring systems for conductors, which results in a big reduce of the cost on ice accretion monitoring.To accomplish the task, the effects of the environmental parameters on the difference of the ice thicknesses on OPGWs and conductors are explored. The main content is as follows.(1) The theoretical analysis of the difference of ice thickness between the OPGW and the wire. The effects of diameter difference, load current, ambient temperature and wind speed on the difference of ice thickness between the OPGW and the wire are analyzed with the help of existent empirical models and formulas.(2) The calculation of the difference of ice thickness between the OPGW and the wire. It is shown that the ice thickness difference between the OPGW and the wire is proportional to the radial velocity difference of water drop on the cable surface during the dry growth process of ice accretion. The velocity of water drop around the OPGW and the wire is computed by using FLUENT, and the effects of diameter difference, load current, ambient temperature and wind speed on the difference between the radial velocity of water drop on the OPGW surface and on the wire surface are examined. Futhermore, the effects of those factors on the difference of ice thickness between the OPGW and the wire during the dry growth process of ice accretion are investigated.(3) The experimental study of the difference of ice thickness between OPGWs and wires. An experiment system is set up and some experiments are run to study the effects of diameter difference, load current and ambient temperature on the difference of ice thickness between the OPGW and the wire, under the condition that the thermal effect of the load current is considered.(4) The regression analysis of the difference of ice thickness between OPGWs and wires. The fitting model of the ice thickness difference between the OPGW and the wire is selected through the long time icing experiment. A linear regression of the ice thickness difference and time data is carried out and some curves are obtained. And the ice thickness difference between the OPGW and the wire under different conditions is analyzed through the analysis of regression coefficient and coefficient of determination. Furthermore, the data on the growth characteristics of ice thickness difference is multi-linearly regressed, and an equation is produced, which takes cable diameter difference, load current and ambient temperature as the independent variables, and the growth rate of icing thickness difference between OPGW and wire as the dependent variables. The validity of the regression formula is verified.