基于Siemems S7-200 PLC的远程测控

为解决Siemens S7-200 PLC的远程测控需求,采用Siemens TC35i无线通讯模块组成GSM MODEM,在使用SiemensS7-200 PLC自由口的用户通讯协议的基础上,通过上位计算机的人机界面及远程PLC的通讯编程,实现了远程PLC变量存储器字节、字和实数等数据的读写及I/O口的读写操作。测试结果表明,在通讯速率为9 600 b/s时,与远程PLC的通讯误码率基本为零。通讯地域为GSM网络覆盖范围。借此技术,同样可轻松实现其他远程对象的数据采集与测控。

LVDS接口原理和标准及在平板显示系统中的应用

对LVDS工作原理、特点和标准进行分析和研究,并介绍LVDS在平板显示系统中的应用。

A Hybrid Diagnosis Approach on Transformer’s Insulating Oil

The immersed-oil power transformer is so vital equipment in power system that maintenance-engineers take more monitor from transformer’s insulating oil to diagnose what is condition of operation. Then the dissolved gas analysis (DGA) is known for an effective technique on detecting incipient faults in oil-immersed power transformers. In this paper, a practical method is presented which consists of the Roger & Dernenber Ratio Methods, the Linear SVM diagnosis, the Key Gas method and the Specification ANSI/IEEE C57.104 Standard. Thus, incipient faults in power immersed-oil transformers can be directly identified by a report’s form which is so easy understood that we can accurate of diagnosis transformer. The user only keys in the measured data of main gases such as H2, CH4, C2H2, C2H4, C2H6, and CO those gases were must decompose via ASTM-D3612. The diagnosis result was showed in texts. This paper was taken some data from Taiwan and Siemens Power Company to verify the program that was validation and accuracy of the transformer’s insulating oil diagnosis tool.

美国绝缘子标准现状及分析

笔者叙述和分析了美国ANSI、NEMA及IEEE标准中的绝缘子标准体系,以及这些标准的特点。这些标准涉及不同材质、不同型式和不同用途的绝缘子。美国绝缘子标准以ANSI和NEMA标准为主,这些标准主要在美国使用,标准制定的比较详细而且主要使用英制单位,这与我国国家标准通常采用的IEC标准不同。通过详细对比这些标准中主要的试验项目,让各标准相关方了解这些标准的试验方法和判定准则。近些年,ANSI、NEMA及IEEE中的绝缘子标准在国内绝缘子技术领域的产品制造、运行和贸易中越来越多的发挥着一定的作用,对我国绝缘子标准的制修订和实施具有重要的参考价值。笔者还讨论了HDPE绝缘子的性能及相关的标准,中国绝缘子标准体系及美标的借鉴意义。