Research On Residual Current Operated Protective Device Based On Single Chip Microcomputer Of MSP430

With the rapid development of our economy, the electric consumption of our society has a rapid growth. Because of the defects of electrical equipment, the unsuitable use and the ineffective security measures, person may get an electric shock or a fire accident may happen in the process of consuming electricity. It will bring the undue losses of people's life and property. The residual current operated protective device can provide reliable and effective techniques to prevent all kinds of accidents. It can cut off the power supply promptly and protect the equipment and personal security from harm.Firstly, a brief introduction of the development of the residual current operated protective device is given, including the problems in the technology of the residual current protection that we are in face with. The technology of single-chip microcontroller will be used in residual current operated protective device for the design, in order to improve its intelligence. It can meet the diverse needs of users. The residual current operated protective device which is introduced in this paper can detect the real-time residual current value and the residual current operating value can be switched automatically according to the present condition of the power system. When the protection is occurred, the residual current operated protective device possesses the inverse time lag function, ideal time delay and the automatic reclosing function. So all kinds of complicated rural grid and climatic condition can be adapted by the residual current operated protective device, and the safety and the reliability of the power supply can be ensured.Secondly, a design scheme is selected in the paper. The first design scheme is based on combining the hardware controlling with the software controlling. This design scheme does not have ideal operation reliability in the protection and has some other problems. The second design scheme is digital design scheme. The single-chip microcontroller MSP430F149 which is a kind of ultra low-power mixed signal micro-controller is employed as the main controller in the new scheme. Basically, the operation is not dependent on the control of the hardware, but makes full use of the functions which micro-controller itself has. Most of the required functions and specifications are achieved by the control of the software.Then the residual current operated protective device based on the digital design scheme is divided into hardware design section and software design section to expound the design principle and implementation in detail. In the hardware section, the paper introduces the whole hardware system briefly at first, which includes MSP430F149 microcontroller, system power module, LED display module, signal regulation module, relay control circuit, status display circuit and delay time option circuit. For each part, the circuit design and the design method are described in detail. In the software section, according to the modularization design theory and the achieved functions, the whole software design is divided into seven parts, such as the system initialization, data acquisition, data processing, LED display, operation value, operation logic and time interruption. For each part, the flow chart of the software program design and the function realization are expounded in detail.Finally the whole development process is summarized and the further improvement is presented.