Development of a new portable short-circuit grounding device for mining applications

As electrical equipment in coal mines increasingly adopts compact designs, the space within their wiring compartments continues to shrink. Existing short-circuit grounding devices often fail to meet field requirements due to issues such as mismatched installation angles, oversized connectors, poor insulation, inadequate contact, and unstable connections. To address the challenge of installation in confined spaces, research on a wide range of underground equipment revealed that axial installation along the wire binding bolt offers the most practical approach. By utilizing the exposed portion of the bolt and thread engagement to ensure reliable fixation and maximum contact area, a rotary installation method was proposed, along with a ring-type terminal designed to prevent the grounding wire from twisting during installation. The grounding wire is selected based on the maximum three-phase short-circuit current in the coal mine, and an epoxy resin insulated handle of appropriate length is configured according to the voltage level, effectively resolving the aforementioned issues. Test results show that operators can complete the installation on the equipment's wire binding bolt within two minutes without twisting of the grounding wire. After applying three mutually perpendicular forces, the device showed no signs of loosening. It withstands the maximum short-circuit current at the installation point and reliably discharges to ground until the switchgear trips, ensuring the safety of both personnel and equipment.