Characterization of a Raman-based distributed fiber optical temperature sensor in liquid nitrogen

Distributed Temperature Sensor(DTS)based on Raman scattering have a promising application in temperature monitoring and quench detection of high‐temperature superconducting(HTS)fiber optic cable.In this paper,a series of mechanical property tests were carried out on fiber optical cables with different encapsulation materials to select the best material for the engineering environment.This was followed by loss testing of fiber optic cables with different outer diameters under liquid nitrogen(LN_(2))and the optimal outer diameter to meet measurement accuracy and engineering practicability was determined.Finally,the temperature measurement of fiber optic cables laid on HTS fiber optic cables were calibrated using thermocouple as a reference.The results of this research results provide a suitable fiber optic cable for engineering applications.At the same time,it provides a reference for the selection of optical cable structure parameters in HTS optical cable projects.

Analytical analysis of hollow CORC cable under thermo-mechanical loads

According to engineering experience,the axial shrinkage caused by the refrigerant seriously endangers the performance of long‐distance conductor on round core(CORC)cables.Since outage maintenance of high‐temperature superconducting(HTS)cables is inevitable,providing appropriate compensation for cyclic temperature is one of the key technologies in the actual application of power cables.Therefore,this paper presents an analytical solution for hollow CORC cables under thermo‐mechanical loads.First,regarded as an axisymmetric composite structure,the radial temperature distribution of CORC cable under Dirichlet boundary or mixed boundary conditions was calculated.Then,assuming cable ends were axially fixed,a recursive method without variables is used to evaluate its displacement,strains,and stresses.Then,an algebraic method with axial strain as a variable is developed to analyze the mechanical behavior of the CORC cable more directly.Finally,concluded from the above derivation,a matrix equation is constructed based on continuity equations and boundary conditions,which applies to isotropic and orthotropic materials with orientations.Calculation results show that the analytical solution agrees with finite element method(FEM)results.Compared to the trial results of a 360 m CORC cable,the calculation error of axial shrinkage is within 1.63 cm,and the relative error is within 6.1%.In addition,the recursive method is the fastest to calculate axial strain,while the matrix method has a significant efficiency advantage in calculating the stresses and strains of each layer.