Design Of Comprehensive Electric Power Monitoring Instrument

Electric power is one of the broadest sources of energy. With the development of technology and national economy, the demand of electric power which people need is increasing day by day. The electric power resource also becomes gradually shortage. The validity, reasonability of using electric power is considered to be important. To ensure the safe operation of Power Network and understand the status of it, electric power monitoring instrument also plays an increasingly important role as the part of the power management system.The existing electric power monitoring instrument is substituted by the new instrument. The function becomes stronger, more dependable. The usage becomes more convenient. The measurement range becomes wider, and the accuracy becomes higher. The trend of substitution is focused on reliability, advancement, usability, expansibility, and opening.The measurement of electrical energy parameters utilizing A/D and MCU is prevailing solution for electric power monitoring instrument. According to the defects of the long development cycle and complexity of software, a new method is presented. An ATT7022A system for measuring the electric power parameters is employed in the design of comprehensive electric power monitoring instrument. The ATT7022A is a high accuracy 3-phase electrical energy measurement IC. It intergrates the ADC, digital intergrator, reference circuit, power measurement and RMS calculation of the digital processing module. In this paper, the high performance-price SST 8-bit microprocessor is regarded as the core of the comprehensive electric power monitoring instrument. This instrument integrates the function of protection, communication, measurement and control. ATT7022A is adopted to replace data-conllecting hardware circuit. Compared with the traditional method, the peripheral circuit is simplified, the cost is decreased, and the system reliability and accuracy are improved. Moreover, using RS485 communication, data exchange between instrument and host computer is more convenient, and the automation of electric system is realized easily. In this paper, the development of electric power monitoring instrument is described, basic principle and the step method of the intelligence instrument development are explained, and the characteristics of ATT7022A and SST microprocessor are introduced. According to the technical requirements and functional characteristics of the system, the realization scheme of the system and hardware are decided. The system is devided into seven parts such as measurement unit, computing processing module, man-machine interface, communication interface, input and output modules, data storage module, reset and power monitoring circuit. Based on the system scheme, the software and hardware process of every part are described in detail. Through the software and hardware debug, the experiment results show that the electric power monitoring instrument function are stable, all indexes can meet the basic technical requirements.