Deep-Soil Acoustic Backscatter Networking for Electrical Substation Grounding Assessment

Electrical substation grounding integrity is fundamental to power system safety, yet its long-term performance is strongly influenced by soil conditions that are difficult to monitor continuously. Existing underground sensing approaches are largely ineffective due to severe signal attenuation in soil, strong electromagnetic interference, and frequent exposure to high-voltage strikes. In this work, we present SoilCapsule, a distributed, battery-free, capsule-style acoustic backscatter sensing system for substation grounding assessment. SoilCapsule harvests ultrasonic energy for computation, sensing, and communication, making it inherently resilient to high-voltage strikes. We design, prototype, and experimentally evaluate the complete end-to-end system. Experimental results show that the proposed grid-to-soil power delivery approach can energize sensors buried at a depth of 100 cm while requiring only 6.17 ppm of the transmit power needed by conventional surface-to-soil schemes to achieve comparable depth. Finally, a field deployment of 20 SoilCapsule sensors in an operational medium-sized electrical substation demonstrates the feasibility of long-term grounding monitoring in real-world environments.