An ARM Based Switching Unit For Automatic Test Of Grounding Grids

To reduce the manpower and improve the working efficiency in grounding grid corrosion diagnosis, an automatic test system for grounding grid corrosion diagnosis is presented.The automatic test system, which consists of four parts, such as, the host computer, the controllable DC current source, the programmable digital voltage meter and the intelligential switching device. And the hardware of intelligential switching device which includes ARM based micro-processor LPC2210,hall sensor,relay,analog multiplexer and capacitor storage based backup power supply are designed and realized. According to which, the functions of automatic shift the current excitation positions and voltage measurement positions, automatic switch the excitation polarity and control the output current level are accomplished.Based on the micro-processor LPC2210 and the embedded operating system(?C/OS-II), the software of the system is developed on the platform ADS1.2. The host computer sends the control commands through the UART to the intelligential switching device. After which, the intelligential switching device take the relevant actions according to the commands. Even on the condition of sudden outage, the contacts of the relay can be kept stable by the capacitor storage based backup power supply till the current returns to zero. The software Modules includes the communication with the host computer, auto-control of the excitation and measurement positions, excitation polarity and the output current level.An experimental grounding grid with 60 branches is tested by the proposed system. The functions of communicate with the host computer, auto shift of the current excitation and voltage measurement position and the control of the output current are tested. The results show not only the common functions of communication and control are accomplished but also the contacts of the relay can be kept stable by the capacitor storage backup power supply during the outage, so that the relays won't be damaged due to the non-zero current.