Devices Based On Dual-cpu System, A Small Current Grounding Line

The non-solidly earthed system with the advantage of high reliability has been widely used in power distribution network. But if single-phase fault occurs, long-time running with fault would probably cause multi-points earthed, and arcing earthed fault could lead the system high voltage. So the fast and accurate fault line selection has great significance on the safety and stable running of the system. However, for the fault current is very small and the arc is unstable, there hasn't been a proper approach to solve the fault line selection problem.This paper processed a scenario of fault line selection based on fuzzy logic, which use injection method combined with the criterion based on the incremental of the active component of zero sequence current and the criterion based on transient max of zero sequence current to form a fuzzy logic module. This module is built by the designing of membership function and effective coverage of every criterion and then the weighing of the fuzzy sets of the criterions' results. Then the scenario could achieve final results after the fuzzy decision according to the construction state of the system and the real-time fault data. This adaptive method could overcome the disadvantage of single criterion. It has significantly improved the accuracy by using multiple criterions, the membership function and the weighing of the fuzzy sets.This paper designed a hardware platform based on dual-CPU system to carry out this complicated scenario. Dual-CPU means SCM combined with DSP. So dual-CPU system is formed with two modules centering on SCM and DSP respectively. The management module centering on SCM are mainly in charged of the management of the whole equipment, including fault detection, fault line selection, human-machine interface and serial port communication. The data-processing module centering on DSP are responsible for the processing of the injection signals and zero sequence currents including transient and steady states from 36 feeders of substation. This paper presents the overview designing of the equipment including hardware structure and function and software process. Besides that, every function part of hardware platform has a detailed description of the hardware structure and the software realization.The equipment this paper designed employed the LCD device controlled by T6963C and little keypad to form the interface hardware platform, and used RS232 and RS485 communication protocols to have serial port communication, which used in the communication with debug machine and network respectively. For the realization of the good human-machine interface and network capacity, this paper has a detailed illumination of the software designing of the interface and serial port communication And for the port maintaining in the on-site debugging, this paper processes the overview designing of the software platform using VC and also a detailed description of its realization. The equipment this paper designed has been preliminarily verified in the lab.