Electrical accidents are the 4th leading cause of death in mining and are disproportionately fatal compared with most other types of mining accidents. Electrical shock causes over 90% of all mine electrical fatalities. About one-fifth of these deaths result when high-reaching mobile equipment contacts power lines overhead. Burns are the leading cause of electrical injury by a nearly 2-to-1 margin. They typically result from non-contact electrical arc flashes which can produce temperatures as high as 35,000 degrees F. Pressure waves from the rapidly-heated air cause secondary injuries such as blunt-force trauma, cuts, abrasions, and hearing damage. One-half of all mine electrical injuries and fatalities occur during electrical maintenance work, with the following electrical components most commonly involved: circuit breakers, conductors, batteries, and meters. The wide variety of electrical injuries on-the-job suggests that no single intervention strategy can eliminate occupational electrical fatalities and injuries. Instead, multi-faceted research approaches that consider not only engineering controls but also organization of work, training, and personal protective equipment are needed to mitigate electrical hazards. The work in this topic area is supported by the NIOSH Mining Electrical Safety and Communications program. See the NIOSH Mining Products page for software, guides, training materials or other items related to this topic.
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Data & statistics
Electrical Accidents in the Mining Industry, 1990-1999 (PDF, 81 KB, 2003)
This NIOSH study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied.
Occupational Electrical Injuries in the United States, 1992-1998, and Recommendations for Safety Research (PDF, 214 KB, 2003-08)
Data show that 2,287 U.S. workers died and 32,807 workers sustained days away from work due to electrical shock or electrical burn injuries between 1992 and 1998. The narrative, work activity, job title, source of injury, location, and industry were examined and a primary causal factor was identified for each fatality.
Measurement & analysis
Detrimental Effects of Capacitance on High-Resistance-Grounded Mine Distribution Systems (PDF, 3313 KB, 2006-09)
Modern underground coal mines can be very large, having a total connected load in excess of 15,000 hp. These, mines generally have many miles of high-power conveyor belts and 15 or more miles of high-voltage power cables at distribution voltages of 12.47, 13.2, 13.8, or 14.4 kV.This paper addresses the potential detrimental effects of capacitance charging currents during line-to-ground faults in mine power distribution systems. A representative mine power system is modeled, and simulations with faults at various locations are conducted to evaluate the effects of this capacitance on the level of fault current and relay selectivity. This paper also includes results of capacitance measurements made on mine power feeder cables used to validate the simulation model.
Distributed Measurement of Conductor Temperatures in Mine Trailing Cables Using Fiber-Optic Technology (PDF, 63 KB, 1998-03)
Mine trailing cables operated above safe thermal limits can cause premature insulation failure, increasing electrocution and fire hazards. This paper describes a unique approach to measuring temperatures within reeled cable under dynamic test conditions.
Dynamic Temperature Measurement of Overheated Shuttle Car Trailing Cables in Underground Coal Mines (PDF, 220 KB, 1999)
A method is described to measure the conductor temperature of mine trailing cables during normal operation. The temperature is measured using an optical fiber located in the center of the metallic conductors.
Reducing Non-Contact Electric Arc Injuries: An Investigation of Behavioral and Organizational Issues (PDF, 259 KB, 2007-11)
NIOSH investigated behavioral components associated with arc flash incidents in the mining industry and recommended interventions based on the findings.
Trends in Electrical Injury in the U.S., 1992-2002 (PDF, 329 KB, 2008-07)
This paper updates an earlier report by the authors that studied electrical injuries from 1992 to 1998. The previous information is expanded and supplemented with fatal and nonfatal injury rates and trends through 2002. NIOSH research aimed at evaluating commercially available overhead power line proximity warning alarms is described.
Trends in Electrical Injury, 1992-2002 (PDF, 249 KB, 2006)
Injury numbers and rates are used to compare and trend electrical injury experience for various groups and categories. This information allows identification of at-risk groups that could most benefit from effective electrical safety interventions.
Understanding and Quantifying Arc Flash Hazards in the Mining Industry (PDF, 398 KB, 2007)
This paper presents characteristics of past arc flash hazards in mining; a review of important concepts needed to understand these hazards; methods for identifying, measuring and managing arc flash hazards, and results from a detailed arc flash hazard analysis.
Engineering controls
Derating Factors - For Round and Flat Mine Trailing Cables (HTM, 2000-08)
Concerns about the present derating factors used for reeled trailing cables prompted researchers at the NIOSH Pittsburgh Research Laboratory to determine new derating factors for reeled coal mining trailing cables. In particular, the new derating factors focus on mine trailing cables used on shuttle cars, with both round and flat cable configurations, that are representative of mining industry usage.
Detection of Downed Trolley Lines Using Arc Signature Analysis (PDF, 2300 KB, 1997-05)
The article discusses the applicability of computerized signal analysis techniques to identify fault currents existing on coal mine direct-current trolley systems
Distinguishing Motor Starts from Short Circuits through Phase-Angle Measurements (PDF, 156 KB, 2002)
NIOSH investigated how the starting of induction motors may cause nuisance tripping of short-circuit protection on coal mine power systems.
Early Detection of Insulation Failure in Electric Motors (PDF, 1500 KB, 1993)
This article describes the development of adaptive learning networks (polynomial networks) to detect and quantify winding insulation leakage on electrical motor windings. This is part of a project to detect impending component failure in mine electrical power systems.
Electric Shock Prevention (PDF, 1852 KB, 1978-10)
Electric shocks are a serious problem in the mining environment. Electrical accidents, resulting in personal injury, due to improper or complete lack of grounding of electrically operated mining machines, form a significant percentage of the overall electrical accident picture. The object of this paper is to describe methods of detection of unsafe electrical conditions with respect to the grounding of electrically operated mining equipment.
Feasibility Study to Reduce Injuries and Fatalities Caused by Contact of Cranes, Drill Rigs, and Haul Trucks with High-Tension Lines (PDF, 122 KB, 2001)
Overhead electric power lines present a serious electrocution hazard to personnel in a variety of industries. This paper describes a practical low-cost concept to detect actual contact of mobile equipment with a high-voltage line and provide a warning.
Investigation of Ampacity Derating Factors for Shuttle Cars Using Fiber Optics Technology (PDF, 256 KB, 1997-10)
A method is described to determine dynamically the conductor temperature of reeled shuttle car cables using fiber optics technology.
Protecting Miners from Electrical Arcing Injury (PDF, 499 KB, 2007)
This paper describes how NFPA 70E - Standard for Electrical Safety in the Workplace can be applied to mining workplaces after an analysis of the mine power system electrical arcing hazards has been completed (and Hazard/Risk Categories determined) using the tables from NFPA 70E or the calculation method as described in IEEE 1584. Appropriate lockout and tagout procedures for use in the mining industry, suggestions for better selection of electrically-rated hand tools, and recommendations for electrical meter selection and use are also discussed.
Training
Noise Exposure and Overhead Power Line (OPL) Safety Hazards at Surface Drilling Sites (PDF, 2968 KB, 2005-11)
This is a series of 5 separate double sided sheets designed to educate workers about noise exposure and overhead power line safety at surface drilling sites.
Videos
Arc Flash Awareness
This video provides information about arc flashes.
Laboratories
Mine Electrical Laboratory
A safe, secure, and properly equipped facility for conducting mine electrical safety research.
Facilities
DC Trolley Railway System
A test bed for experiments involving DC trolley/track haulage equipment.
Information gateways
Traumatic Occupational Injuries: Electrical Safety
NIOSH electrical safety information. Traumatic Occupational Injuries: Electrocution Fatality Investigation Reports
Fatality investigation reports of cases where electrical incidents resulted in the deaths of workers.
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