Application of GF-GC Monitor for Trailing Cables in Coal Mines
GFM100 ground fault ground check monitor has been put into service at the Xilinhot Coal Mine
Trailing cables for mobile electrical device such as shearers and roadheaders in coal mines are subject to long-term dragging, rolling, and friction and impact from gangue. The internal ground check core wires of the cables are highly prone to disconnection and poor connection hazards. Such faults are highly concealed and difficult to detect in advance through manual inspection. Once the ground check core wire fails, if the cable insulation is damaged and electric leakage occurs on the device enclosure, conventional earth leakage protection may fail, which can easily lead to electric shock accidents and even gas explosions. This constitutes a major challenge for power supply safety management and control in coal mines.
To address this on-site challenge, the Sikcon GFM100 ground fault ground check monitor has been put into service at the Xilinhot Coal Mine in Inner Mongolia, providing an integrated monitoring solution covering ground faults and grounding continuity for coal mine trailing cables. The complete device system consists of the GFM100 ground fault and loop detection main unit, the GF12 Zener terminal module, and a zero-sequence current transformer (CT). The system relies on the zero-sequence current transformer to collect zero-sequence current of the power circuit in real time to monitor single-phase earth leakage faults. Meanwhile, the GF12 Zener terminal module and the built-in detection core wire of the cable form an independent monitoring loop, which continuously checks the continuity of the ground check circuit between the feeder switch side and the equipment terminal. When disconnection or short-circuit faults occur in the check core wire of the trailing cable, the device can quickly identify the fault type, output an alarm signal independently, and interlock the feeder switch for tripping. It can clearly distinguish between leakage faults and ground wire disconnection faults to facilitate accurate handling by maintenance personnel.
The GFM100 offers flexible protection setting. The ground protection supports 11 adjustable tripping thresholds (0.5~50 A), matched with 11 stages of definite-time delay (0.1~2.5 s). This enables graded selective protection on site and avoids maloperation of over-tripping. The device adopts a 30 VDC safe voltage for loop resistance sampling to reliably detect open circuits and short circuits. It features excellent vibration resistance and electromagnetic interference immunity. Parameters can be set locally to adapt to trailing cables of different lengths. Equipped with an RS485 Modbus communication interface, the device can upload fault alarms, event logs and other data to the coal mine automatic monitoring platform to support remote online monitoring from the surface. The passive relay output interface can be directly connected to the switch interlock circuit to reliably block the power supply channel upon fault occurrence.
This device fills the gap of traditional protectors which cannot online monitor disconnection of the ground check core wire of trailing cables. It complies with relevant coal mine safety specifications, realizes all-weather online monitoring of the grounding integrity of trailing cables, effectively eliminates concealed power supply safety hazards, shortens fault location and handling time, safeguards the power supply safety of underground mobile equipment, and supports the construction of intelligent power supply systems in coal mines.
