Optical fiber distributed sensing of temperature, thermal strain and thermo-mechanical force formations on OPGW cables under wind effects

Optical ground wire (OPGW) is generally used to protect the phase conductors of the overhead power cables from high discharge currents due to lightning strikes and instantaneous current increase due to short-circuits or breakdowns as well as to provide data transmission for telecommunication purposes. OPGW cables are exposed to effects of environmental factors such as wind, rain, humidity and snow as well as cooling/heating effects of short-circuits and instantaneous current increases occurring on the phase conductor. When the OPGW cable is exposed to those effects, deformations occur on the cable insulation in time. In this study, using Raman effect based optical fiber distributed temperature sensing (DTS) method, temperature and thermal strain variations occurring along the OPGW cable due to environmental conditions, in particular wind speed and wind direction, have been analyzed and simulations have been performed. Furthermore, thermo-mechanical forces occurring on the OPGW cable have been expressed as a function of temperature change and Young modulus variations. Temperature and thermal strain dependencies of thermo-mechanical forces have also been derived. Using results of the theoretical analysis, simulations of thermo-mechanical force variations along the sensing fiber have also been performed considering the wind effect. The simulation model has been built up for central loose tube type OPGW cable containing single mode optical fiber operating at 1550 nm. For wind speed variations between 5.3 m/s and 10.3 m/s, minimum temperature detected on the cable varies between 26.86 °C and 22.41 °C, respectively, minimum thermal strain varies between 184 με and 64.67 με, respectively. Simulation results show that temperature sensitivities of thermo-mechanical forces are 26 times greater than thermal strain sensitivities.