Research On Digital Protection And Model Of Sampled Values

With the development of the novel electronic transducer, the parallel wiring to link the process level and the bay level of substation automation system will be replaced by serial optical cable, and it is a technology renovation of the substation automation. To realize interoperativity among the IEDs is the aim of substation system. Firstly, this thesis introduces the production, development of IEC 61850 and its influence on substation automation system. Then the constitution thoughts, characteristics and standard system content of IEC 61850 are introduced in detail. At last, this thesis deals with the transmission of the sampled values, the significant achievements are as follows:The constitution thoughts, characteristics and standard system content of IEC 61850 are introduced, the model of substation is given, the general information of IEC 61850 is understood; For the distance protection, modeling approaches of the sampled value model is proposed. On the basis of in-depth analysis of sampled value model, the sampled value model is constructed and mapped in a specific way, a favorable theoretic basis is supplied to realize the digital transmission of sampled values; A CPLD based method to interface the electronic transducer is proposed. The key to connect the electronic transducers with digital output and new protective devices, called Merging unit, is analyzed in depth. Sampled values from several electronic transducers can be received using CPLD, the validity of which can also be checked by means of cyclic redundancy code checker. The Asynchronous Serial Communication, Cyclic Redundancy Code, Receive Unit Based on VHDL are proposed, the method of serial transmission is also given; In order to use the current protective devices into the new system, the reconstructure of current protective devices is proposed. The key of the reconstruction is analyzed; the change of hardware block and the communication model are given. At last, the model of digital protection devices is also given, which sets the basis of digital protection.