Reasch And Development Of The Micro-processor-based Line Synthetical Protection Device

Study of transmission line protection of power system is always the most activesubject in the field of relay protection. Today,along with microprocessor-basedprotection has been used widely,the study of protection also has already developed tohigh performance and synthesized level. The chief method of this paper is aboutdeveloping the microprocessor-based line protection device based on DSP technique.It also gives enough study and profound exposition on protection principle and designof software and hardware.Algorithm is one of focal points in study of microprocessor-based protection. Atfirst, we make emulations, aiming at full-wave fourier algorithm and semiwavefourier algorithm. Then their merits and demerits are shown respectively throughanalyzing their frequency response and time response. Subsequently is it manifest thatthere are some influences on fourier algorithm if the system frequency deviates fromnormal level. In order to diminish those influences and increase operating reliabilityof protection device,a new algorithm of frequency measurement and tracking ismentioned in this paper. Then many emulation results about this algorithm indicatethat it has higher precision and faster response speed.The configuration of low-voltage line protection device based on new algorithmis proposed, including overcurrent protection, sheding, reclosing and its accelerationprotection and overload protection. The analysis of protection principle and its logicdiagram are also shown in the paper. The results of dynamic test have proved thevalidity of the protection device in line protection and control,and it can meet all thedemands of power systems.The stability and reliability of hardware is very important to the implementationof protection functions. The designed device based on dual CPU structure: DSP andMCS-51, is a synthetical line protection including measurement and control. DSP isused to accelerate data processing,and dual CPU configuration can increase thereliability of the device. Moreover,relay protection,measurement,control,data-communication function are involved as a whole unit in this device for fulfillingthe needs of the developing of power system and its automatization.