Electrical Safety for Underground Mining

The hoist must take the equipment and miners up and down the shaft and bring ore to the surface for processing. The drive used on the hoist is a large electric motor powered by a frequency converter. The floating or high-resistance grounding system is used as the dominant grounding system to ensure maximum security. Bender manufactures the ISOMETER® for optimal electrical safety in underground mining.

Ventilation of underground mines is crucial for safe operation. An interruption to the ventilation is potentially life-threatening. It can also create the potential for a build-up of gasses creating a fire hazard and loss of production due to mandatory evacuation. This means continuous ground-fault monitoring using RCMS is vital. Insulation resistance monitoring provides early detection of insulation breakdown and can assist in preventative maintenance planning.

Drainage of underground mines is essential. Any interruption to the drainage system increases the risks of shafts filling up with water ruining equipment, and people being put in danger. From this perspective, continuous insulation monitoring with ISOMETER®s or RCMS residual current monitoring systems (ground-fault monitors) is essential. Early detection of insulation degradation can help prevent prolonged and unnecessary downtime. Where portable trash pumps or submersible pumps are handled, additional safety precautions should be taken by installing Bender Lifeguard units for personnel protection.

Electric motors are generally employed for conveyor belts used in mining, driven by soft starters or frequency converters. However, these often generate harmonics and DC currents which would typically not be present in an AC system. With regular ground-fault protection or simple insulation monitors (e.g. 3 lamp method or 2 voltmeter process), these circuits cannot be monitored and adequately protected. These specialized applications require more modern monitoring equipment which can recognize and report insulation breakdown and leakage current to ground quickly. Some standards even require a quick shutdown, which can be achieved via ground-fault monitoring devices.

Mining equipment is typically electrically powered. The trailing cables powering these vehicles need monitoring. The monitoring ensures proper bonding of the equipment to prevent hazardous shock potential on the frame. For these applications, Bender offers a range of monitoring options, depending on the requirements for pilot-wire (ground-check) monitoring, ground-fault current protection, or ground conductor monitoring. If the equipment being powered is DC, the ISOMETER range of products can be applied.

Substations feeding power to moveable and mobile loads are often required to be resistance grounded. Some standards require continuous monitoring of the neutral grounding resistor. The Bender RC48N and NGRM700 are ideal choices for this protection. Outgoing trailing cables can be monitored with an RC48C ground-fault ground-continuity monitor.