小电流接地选线装置可编程采样系统设计

在分析了小电流接地选线装置采样系统特点的基础上,介绍了以复杂可编程逻辑器件(CPLD)为核心的可编程采样系统的结构及其设计方法.给出了可编程采样系统的整体设计方案,利用CPLD强大的硬件可编程能力实现系统采样频率和采样通道数的可编程设置,介绍了其原理和特点.介绍了"异或"状态机,分析了其工作时序,利用其状态的改变实现采样频率的可调;设置模值可变计数器来实现采样通道数的设置;用状态机控制AD的工作时序,实现AD与CPU工作的分离;用CPLD控制采样通道的转换,读写转换数据.结合分析AD采样时序的控制,设计出了采样频率由输入方波频率决定,采样通道数由CPLD寄存器设定的采样系统.其仿真结果表明,该方案可行,有较好的稳定性和通用性.

Design of programmable sampling system in fault line selection device for small current grounding system

The sampling system of fault line selection device for small current grounding system is analyzed,and the structure and its design of the programmable sampling system with CPLD(Complex Programmable Logic Device) as its core are introduced.The overall design scheme,as well as its principle and characteristics,are presented.With powerful CPLD,the sampling rate and channel number of the system are programmable.The "XOR" state-machine is inbtroduced and its time sequence is analyzed.The sampling rate is adjusted by changing the state and the sampling channel number is set by building a value-changeable counter.The working sequence of AD is controlled by the state-machine,being separated from CPU.CPLD controls the switching of sampling channel and the reading and writing of converted data.By analyzing the control of AD sampling sequence,a sampling system is designed,in which the sampling rate is decided by the input square-wave frequency and the sampling channel number is set by a register in CPLD.Simulation results indicate its good feasibility,stability and versatility.