Temperature control and monitoring system for power transformer windings using fiber optic sensors
On-line monitoring of function and condition parameters and the efficiency of the cooling system are key elements in determining the working condition of transformers. This paper presents the implemented hardware and software solutions for carrying out the winding temperature on-line monitoring system using fiber optic sensors. The actual winding temperature is a measurand which defines the condition, load capacity and operating life of transformers. By carrying out the temperature control and monitoring system for power transformer windings using fiber optic sensors, ICMET Craiova aligned itself to the requirements of the international standards.
Real-time Temperature Monitoring System Using FBG Sensors on an Oil-immersed Power Transformer
Over-heating issues will affect the safe operation and life-time of an oil-immersed transformer; therefore, it is necessary to monitor the temperature of the windings and oil during a transformer's operation. Fiber Bragg Grating (FBG) temperature sensors are installed to measure the temperature of windings, cores, and busbars, as well as oil temperature at the top and bottom. An online-monitoring system is used to collect and analyze temperature data over time. Analysis shows that, by using the fiber optic Bragg grating temperature sensors, the internal temperature of an oil-immersed trans- former is accurately monitored in real-time. Additionally, the result can be used as good evidence to evaluate the service life and operational state of a transformer.
Fiber Bragg Grating Sensors
This article reviews the principles and application of optical fiber Bragg gratings (FBGs) as strain and temperature sensors for structural health monitoring applications. FBG sensors have many advantages for strain sensing in such applications including their small size, the potential to multiplex hundreds of sensors with a single ingress/egress fiber, their immunity to electromagnetic interference, and their corrosion resistance. The spectral properties of FBGs and their response to applied strain and temperature fields are derived. Multiplexing and interrogation strategies for large sensor networks are presented. Special focus is placed on the response of FBGs to multiaxis strain fields and rapidly varying strain fields such as near the location of structural damage. Common approaches to invert the spectral response of an FBG subjected to a complex strain field are also reviewed. Finally, this article reviews common fabrication techniques for FBGs and their relative impacts on the strength of these sensors. 
 
 
Keywords: 
 
optical fiber sensor; 
fiber Bragg grating; 
long period grating; 
wavelength division multiplexing; 
multiaxis sensor