Development On Protection Device Based On DSP For Distribution Power Line

Distribution power line supplies power to users directly. Its reliability is very important. With the development of power distribution automatization and the improvement of power substation integrated automatization, the demand for distribution power line protection and supervisory control is becoming more and more strict.This dissertation analyses and compares the microcomputer-based protection and measurement algorithms used in power system. Least squares algorithm is researched deeply. A new method of analyzing measurement error of Least squares algorithm is presented. The relation between Least squares algorithm and Fourier algorithm is discussed. Relay protection functions used in this dissertation are explained in detail and the sensitivity of no time-limited current protection is improved with self-adaptive principle. After referencing the developed similar devices, this dissertation puts forward to develop an advanced low voltage distribution power line protection device with TMS320F2812 DSP. The structure of this device is simplified by using A/D module inside DSP and the cost is reduced. Experiment shows that it achieves the designed technology requests. The main structure of the device, the selection of the CPU, the design of analog inputs, and the A/D sampling method are argued in detail in this dissertation. And the selection and design of DI(Digital Input) module, DO(Digital Output) module, communication module, clock module, keys module and frequency detecting module are also discussed. Lastly, according to the device's technology request the hardware circuit is chosen and the hardware design is finished. The system software uses typical up to down and modular designing methods. In this dissertation, the total frame of main program and the A/D sampling interrupt program are analyzed. And several problems in software designing and debugging are summarized in this dissertation at last.Experiment result shows that this device completes the function of kinds of current protections and alarms. It realizes the accurate measurement, calculation and display of measuring data. This dissertation presents a feasible scheme for application with high-performance DSP in power system.