Fiber optical systems are becoming increasingly important for measurement of current and voltage in high voltage environments. Conventional electrical wiring such as transmission line for voltage transformers can readily be replaced by noise-free fiber optics. A novel active voltage transformer with an optical data communication link has been demonstrated. The system includes a transducer based on the capacitive divider and two electrically isolated signal conditioning sections with optical fiber communication link. The proposed solution allowed for designing and developing a novel and high-performance voltage transformer for in-field application. A prototype version of the transformer was constructed following the new standard, with digital output interface to protection devices and the experiment results confirmed a 0.2 accuracy class.
This paper describes techniques for improving the accuracy and stability of the optical voltage transformers (OVT), which are affected by temperature around circumstances. Higher accuracy and stability is achieved by two light- channels compensation method, which uses one polarizing beam splitter. Many test show that this compensation method can eliminate the effects of unwanted birefringence induced by temperature and around circumstances of OVT effectively. OVT which uses this compensation method has passed the type test with accuracy and stability within +/- 2 percent.
The stability of optical voltage transformers has been the main obstruction to its practical application. An optical voltage sensor is the core of an optical voltage transformer. This paper proposed a novel reflection-type transverse modulation optical voltage sensor with double light channels temperature compensation. The sensor is based on the Pockels effect in a Bi4Ge3O12 (BGO) crystal. The measured voltage is applied to the crystal along the <001> direction with light wave passing through the crystal along the <110> direction. Theoretical analysis shows that this is an optimum configuration for a reflection-type transverse modulation optical voltage sensor. The novel optical voltage sensor was employed to develop a novel optical voltage transformer (OVT) for 220 kV power systems. There isn't any capacitor divider in the OVT. The measured high voltage is applied to the optical voltage sensor directly. Experiments showed that the sensor has good double light channels temperature compensation characteristic and the stability of the OVT could reach +/- 0.4% during two weeks. The principle, structure and test results of the OVT are presented in this paper.
This paper focuses on the fundamental issues related to the development of intelligent CAD/CAM systems for progressive dies which are used for manufacturing sheet metal parts in mass production. The CAD/CAM functions for sheet metal product design and those for design and manufacture of progressive dies are defined by studying the sheet-metal-product life cycle. The procedures of industrial design and manufacture of progressive dies are reviewed, and the need for intelligent CAD/CAM systems identified. The platforms, environment, and key technologies for the systems design and implementation are discussed. Finally, a prototype CAD/CAM system for progressive dies is introduced.