Research On The Combined Electronic Transformer

Transformer is an important equipment of electric parameter data acquisition in the electric field, which can be divided into electromagnetic transformer and electronic transformer. Comparing with the traditional transformer, electronic transformer has a lot of advantages such as small size, good linearity, high safety coefficient and low cost in the measurement performance and manufacturing. And electronic transformer is more suitable for the development trend of today’s power system. In order to get higher measurement accuracy, more information, and meet the needs of highly integrated information processing development, a recombination type electronic transformer on the basis of the comprehensive analysis of electronic voltage transformer and electronic current transformer is designed. Then, the question that need to be noticed during the process of accuracy improving are illustrated.The design uses capacitive divider, Rogowski coil measurement, and low power coil as sensing head by analyzing the performance and the characteristics of various types of electronic transformer. Some specific countermeasures are put forward after analyzing the factors which influenced electronic transformer. The designing of the transformer structure is accomplished.In order to improve the measuring accuracy and stability of the composite type transformer, the change-over circuit which contains integral and amplitude modulation is designed. At the same time, the protection and shielding at the circuit board and the power supply are designed to reduce the influence on the conversion circuit. In order to eliminate the influence of core saturation of the low power coil, data integration of Rogowski coil and LPCT is designed. It realizes the switch of output signal between the two types of transformer, and improves the applicability of transformer.In order to illustrate the feasibility and performance, the prototype is made and the testing device and the process are designed. The test results show that the phase-sequence and zero-sequence current can meet the accuracy requirements of GB/T 20840.8-2007 standard 1 and 3 class and phase-sequence and zero-sequence voltage can meet the accuracy requirements of GB/T 20840.7-2007 standard 1 and 1P class.