A distributed temperature sensing system (DTS) is a device made to monitor power cable with fiber optic temperature sensors. DTS measures temperature on the large distances, greater than 30 km. It records the temperature along the cable as a continuous profile. DTS spatial resolution is 1 m with accuracy within ±1°C at a resolution of 0.01°C.
Adding RTTR to distributed temperature sensors allows achieving more precision when measuring high-temperature wire. DTS has some level of uncertainty when it detects the temperature, and its level increases when the conductor operates in an emergency situation. This happens because the conductor heating is detected with the time lag. Also, the temperature differs depending on the loading level. The higher the loading level is, the less precise are the measurements.
What is DTS measuring principle?
Certain factors, such as temperature or pressure, affect the optic cable and change the light transmission characteristics in the fiber. Optical fibers operate as linear temperature sensors when the light is projected in it through scattering to determine the location of the physical effect on the outside.
Optical fiber is made of doped quartz glass, silicon dioxide and has an amorphous solid structure. Its molecules interact with the photons when light falls on the thermally excited molecular oscillations. This process leads to light scattering, also called Raman scattering. The difference between the incident light and scattered light is that the later experiences a spectral shift that is equivalent to the lattice oscillation resonance frequency. The scattered light has three spectral shares, namely the Rayleigh (laser source wavelength scattering), the Stokes line components (lower frequency), and the anti-Stokes line components (higher frequency). Anti-stokes depend on the temperature, hence it is possible to calculate the fiber temperature as a ratio between anti-Stokes and Stokes line components.
What is DTS used for?
Distributed temperature sensing has multiple applications in different industrial segments to monitor power cables, tunnels, and industrial buildings, to detect leakages, and to control high-temperature wires. Recently DTS has been applied in monitoring ecological factors, such as groundwater, rainforests, river streams, etc.