In the paper a review on the potential advantages of optical current transformers points out that it is the technology trend
on the development of current transformer. But there are many more difficulties to be resolved, innovative ideas of
developing optical current transformers must be strengthened.
A high voltage current transformer project based on current thermal effect was introduced, which combined the current
thermal effects and the optical fiber thermometry technology. Fiber optic temperature sensor was the earlier and mature
product among fiber optic sensors in commercial, current thermal effects technology is more general applied, so the new
project has the advantages over other current transformer projects which are now meeting the difficulties hardly to
The relationship between the instantaneous value of measured current and the temperature rise was deduced, and the
mathematical model of the current transformer was established. By use of the mathematical model, in theory, the
instantaneous value of current can be tracked by the temperature output of sensor accurately, so that it can be used to
measure instantaneous value of current. The technical data and features required of the main devices and components can
be provided by use of the mathematical model for technical design of the project, simulation method and experiment
tests were used to prove the availability.
Recently with the invention of fiber optic Bragg grating (FBG), new kind of sensors based on FBG is increasingly challengingly the dominating position of some traditional sensors, because this new device has some intrinsic capability: Such as multiplexing, self- referencing, optical and mechanical reliability, anti-interference. Especially it brings the significant advantages that they are non- conductive and lightweight, which can allow for much simpler insulation and mounting designs as the application voltage up to 1000kV or more to day. In addition, it doesn't exhibit hysteresis and provide a much large dynamic range and frequency response than iron- core conventional current transformer (CT). In this paper a current sense device based on electromagnetic force is presented. A FBG is held on the armature of an electromagnetism by one end. As current pass through the iron coil, the magnetic force of the coil lengthens the FBG. Then the Bragg wavelength will change via current. By measuring the change of Bragg wavelength of the FBG we can build a relationship between the tested current and the Bragg wavelength. In this paper the configuration of the new device, the theoretical analysis and measurement results are given.
Conventional current transformer (CT) is based on the principles of electric magnetic induction with copper wire windings and iron cores, it is widely used in power systems. But it emerges more weakness as the applied voltage and power capacity more and more increase. Over the past 20 years optical current sensors have received significant attention by a number of groups around the world as next generation high voltage measurement devices, with a view to replacing iron-corn current transformers in the electric power industry. In the opposite side of conventional current transformer, optical fiber current sensor provides a solution of the existed problems. It brings the significant advantages that they are non-conductive and lightweight, which can allow for much simpler insulation and mounting designs as the application voltage increase to1000kV or more to day. In addition, optical sensors do not exhibit hysteresis and provide a much large dynamic range and frequency response than iron-core CT. Optical fiber Bragg grating current sensor is the most potential important one among the optical current sensors, but its current transferred sensibility and the capability of anti-variance of temperature and stress still in a lower level. In this paper, a copper coated Bragg grating current sensor are described. The sensibility is improved significantly.
Heating induced by electromagnetic field, such as radio-frequency (RF) and microwave is often used in medical application. MW or RF heating is used in hypothermia and hyperthermia treatments. Hypothermia is a clinical condition in which the internal body temperature is lowered below 35 C . RF heating (at 13.56 MHz or 27. 13MHz) offers a fast, efficient and non-invasive method. Hyperthermia in cancer treatment involves heating ofmalignant tumors to 42.5-43CC for a extended period in an attempt to obtain remission. MW(at 2450MHz) is potentially a useful method for heating deep localized tumors. A serious problem with this heating modality involves the accuracy ofmonitoring and controlling the tissue temperature in the presence of a strong EM field. Conventional thermal sensors such as thermocouples and thermistors are all based on a metallic active element which cannot function in a strong EM field environment. Optical fiber fluorescent thermometry is a better technique to show this problem. In this paper we quantify the factors determining the performance ofthis method, some practical considerations also be described
In the paper a multiplexing remote temperature measurement system based on the Internet is described. It includes the system project diagram, the configuration of hardware and software. This system can be used in the electric power station to inspect the potential defects of electric equipment. In the situation of full automatic operation, the temperature measuring results can be transmitted to the managed center through the Internet for monitor, in a nobody on duty status.
Although the development of fluorescent fiber optic temperature measurement technology have overcome the difficulty of the surface temperature distribution measurement of a rotor of electric machine. The temperature of the conductor (or magnetic) strips which are buried under the surface of the rotor yet not be resolved. A new measuring scheme of fluorescent optical fiber is presented in this paper. It is fully suitable for the above measuring demands. Several fiber probes are assembled with the rotor. The sensor heads are buried under the rotor surface to touch the measuring points. The other ends of the fiber probes are terminated on an optical rotational coupling disc. The induced temperature signals then are sequentially transmitted out to the external of the rotor by another fix fiber. Finally the temperature of the strips is obtained. In this paper we will discuss the selection of light source, the design of light path and derive the theory analysis of dynamic coupling.
The use of fluorescence technique for temperature measurement has developed since 1980's. Such system has many advantages such as protect against electromagnetic interference, endure high voltage, and non-induce burning or blasting. But at present the high cost of apparatus limited the application widespread. A lot of applications are required and these in turn would depend on the technique improvement and cost reduction. A new kind of multi-channel fluorescence temperature measuring system has been introduced in this paper. The number of channels can be designed as many as several hundreds. It is very competitive especially in power station and high voltage electrical equipment systems. This technology evidently decrease the average cost of each measurement channel. A sketch scheme and problems that have been resolved in design as well as the result of test is discussed in this paper.