Design Of The Load Monitoring Terminal For Distribution Transformer Based On Modbus Protocol

Load monitoring terminal for distribution transformer is located at the bottom of distribution transformer monitoring system. It is installed on the secondary side of distribution transformer. It completes the real-time monitoring for run status of distribution transformer through the acquisition of external voltage, current, active power, reactive power, etc, and provides datas which include load prediction, line loss analysis, fault judgment and power quality for the electricity department and improves the economy and security of power network operation on the technology and management.First the paper introduces actualities and development direction of the monitoring terminal and set forth several ways of communication used in transformer monitoring system at present, their respective advantages and disadvantages are discussed. And then, by combinating of practical project, design objectives, idea and scheme of monitoring terminal are expounded. MSP430FG4619 singlechip porduced by TI corporation is used for the core of MCU according to the need of function. Data acquisition part uses the special electric power measure chip named ADE7758,the GPRS module MC55 is used for long-distance wireless transmission of data, the use of LCD module Embedded font provides friendly people - machine interface. The paper provides the course of hardware and software design from the system angle and by means of the module designing thought. The functions are implemented, which include:power parameters measuring, wireless communication,display and data storage.The ways of communication, functional codes and transmission mode of standard modbus protocol are introducted in detail in the paper. On basis of it, its contents format is expanded to satisfy the needs of applications.The paper mainly uses MSP430 software development platform, adopts C programming language, and completes software design task of the monitoring terminal, exchange of datas are completed between master station and terminal through complying with the expansion of modbus protocol Eventually design of the load monitoring terminal for distribution transformer based on modbus protocol is achieved.