The first corrosion detection for the large grounding grid of a 220kV substation was performed based on electrical impedance tomography (EIT) technology. The impedance value of grounding grid branch which represented the corrosion state of metal was calculated using the current and voltage data acquired on-site through injecting a direct current from one down conductor and collecting voltage data from other down conductors. The results indicated that the impedance increase ratio of the No.143 grounding grid branch in test area D was higher than the warning value (>15 times), indicating a breakage has occurred on this grounding grid branch. The two-dimension corrosion image of the whole underground grounding grid was calculated and drawn accurately and visually using the corrosion diagnosis software. The corrosion rate of carbon steel was monitored in the serious corrosion area later, to realize the online corrosion monitoring of grounding grid metal. EIT technology realized the underground grounding grid statues visible exhibition, and could be used to detect the corrosion state, corrosion area and failure location of the underground grounding grid rapidly and effectively. This could reduce the blindness of corrosion detection for grounding grid and provide guidelines on the corrosion maintenance of underground grounding grid in large substation.

Recently, researches based on the Compressed Sensing (CS) become an important direction in the field of signal processing. The newly proposed system called Modulated Wideband Converter (MWC), which breaks through the limit of traditional Nyquist sampling, has presented huge advantages in sub-Nyquist sampling technique. It is composed of several analog channels that alias the signal intentionally before sampling it at a low rate. Then the signal can be reconstructed from the samples by using some commonly used algorithms in compressed sensing theory. It is one of the most successful compressive sampling hardware architectures, but in real hardware implementation, the digital board is fairly difficult to realize. In this paper, we made exploration of the MWC sampling theory and designed a three channels prototype system. To realize the 1  logic waveform, we present using Rocket I/O on Xilinx FPGA. In this way, the hardware system can be simplified so as to implement quickly. Through hardware experiments and algorithm reconstruction, we verify the feasibility of MWC system in sub-Nyquist sampling theory.