Studies on thermal profile measurement and fire detection in a power supply cable of a synchrotron radiation source by Raman optical fiber distributed temperature sensor system

Abstract

The paper presents the work on development and application of Raman optical fiber distributed temperature sensor (ROFDTS). ROFDTS has been used for monitoring the temperature profile and detecting the progress of unforeseen fire events anywhere in a 160 m long power supply cable (current 760 A, DC) of dipole magnets in the Indus-2 synchrotron radiation source (SRS). Indus-2 is a national facility and is being operated in round the clock mode. The sensing fiber could survive in the harsh environment of Indus-2 SRS that consists of bremsstrahlung radiation of 6.7 Rad/h, high magnetic field of 1.5 T and radio frequency (RF) field of 1.27 MV at 505.812 MHz. The fire detecting capability of ROFDTS was first tested on the mock test setup in the laboratory by artificially creating the four hot zones. Each hot zone has the width of 1.0 m in the sensing fiber at the spatial locations of 26 m, 48 m, 70 m and 92 m respectively. An audio-visual alarm was generated when the temperature of the hot zones exceeded the set temperature limit of 50 °C within 30 s of the start of the fire. Finally, ROFDTS system was deployed to measure the temperature profile of power supply cable during ‘no operation’, ‘injection’ of the electron beam current (109 mA with the energy of electrons @ 550 MeV) and at ‘normal operation’ of the electron beam current (145 mA with the energy of electrons @ 2.5 GeV) in Indus-2 SRS. The peak temperature of power cable reached from 26 °C to 44 °C from ‘no operation’ to during the ‘normal operation’ condition of the Indus-2 SRS.