Electrical Accidents in the Mining Industry, 1990-1999

James C. Cawley, P.E., Senior Member, IEEE

National Institute for Occupational Safety and Health

Office for Mine Safety and Health Research, Pittsburgh Research Laboratory

626 Cochrans Mill Road, P.O. Box 18070, 

Pittsburgh, PA 15236, USA

Abstract- This NationalInstitute forOccupationalSafety and

Health study was conductedto 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. Coal and metalnonmetal operator- and contractor-reported data are presented.

All data used in this analysis were MSHA closeout data, except

1999, which were preliminary data. 

Electricity was the 4th leading cause of death reported in mining

despite being the 14th leading cause of injuries. During the

1990s, 1 of every 272 mining accidents resulted in a fatality. In

comparison, 1 of every 26 mine electrical accidents was fatal.

Burns were the leading Nature of Injury in electrical accidents,

but were rarely fatal. Electrical shock caused 70 of the 75

electrical fatalities reported. About one-half of mine electrical

accidents and fatalities were sustained during electrical

maintenance. Small mines experience a disproportionately high

number of electrical accidents and fatalities based on total

average employment. The injury severity for victims of nonfatal

mine electrical injuries does not increase with age in victims 50

years and older, unlike many other types of occupational

accidents. High-reaching mobile equipment is involvedin about

20% of mine electrical fatalities, indicating that overhead power

line hazards needto be addressed. Electrical accident narratives

containing the six most frequently mentioned keywords were

isolated for further analysis. 1,321 narratives containing the

keywords “breaker”, “cable”, “battery”, “ground”, “energized”

and “meter” were analyzed to more accurately determine causal

factors. Technical suggestions for mitigating electrical hazards

are proposed.

I. INTRODUCTION

This study was conducted to focus future researchon the

most significant electrical problems in the mining industry.

In addition, it formed the first phase of a larger effort to

identify electrical hazards common to both mining and other

industries.

The Mine Safety and Health Administration (MSHA) is

empowered by statute to collect detailed information on

accidents, injuries and illnesses that occur in the mining

industry. MSHA also collects information about mines,

employment and production. The accident data are compiled

frominformation onthe MSHAForm7000-1, Mine Accident,

Injury, and Illness Report. Dataonmines(active,inactive and

abandoned), employment and production (for coal mines) are

reported on the MSHA Form 7000-2, Quarterly Mine

Employment and Coal Production Report. Mine operators

are required to report accidents, injuries,illnesses and certain

other “reportable accidents” 1that occur to bothemployees and

nonemployees on mine property. This statutory reporting

requirement has allowed MSHA to amass one of the best

publicly accessible occupational injury databases available in

the U.S. The Mine Accident and Injury(AI) andMine Address

and Employment (AE) databases consolidate several MSHA

raw databases to provide, for example, ready association of

accident narratives with other accident information.

Information for this paper was compiled from the AI and AE

databases covering the periodfrom1990-1999. All data used

in this report were MSHA closeout data except 1999, which

used preliminary data available through the fourth quarter of

1999. 

II. BACKGROUND

Between1990 and1999mining operators and contractors

reported 260,510 accidents, injuries and illnesses from all

causes, including 959 fatalities. Mines reported 1,926

electrical accidents,including75 fatalities. Electricity was the

4th leading cause of death in mining despite ranking 14th

overall as an accident cause. Nonfatal mining electrical

accidents were responsible for 31,370 lostworkdays(LWDs).

The coal industry is made up of two Standard Industrial

Classifications (SICs), anthracite coal and bituminous coal.

Anthracite (hard coal) is a small segment of the coal industry

in terms of both production and total accidents. During the

study period, coal operators reported 129,553 accidents,

injuries and illnessesfromall causes,including 379 fatalities.

The number of active coal mines (those characterized by

reporting 1 or more hours of work in a given year) fell each

year from 4,320 in 1990 to 2,301 in 1999 and coal operator

employment decreased 43%, from 145,887 to 82,907. Coal

contractor employment, however, increased by 40%, from

21,938 in 1990, to 30,812 in 1999, peakingat 32,201 in 1997.

LWD accidents from all causes reported by coal operators

showeda decline of 73%, from11,381 casesin 1990 to 3,055

in 1999. 

The metal-nonmetal (MNM) sector is made up of 86

different SICs representing a wide range of commodities,

 

1

 For a more precise definition of “reportable accidents” see [1].
2 of 8

TABLE 1

PERCENT OF MINING ACCIDENTS THAT RESULTED IN A FATALITY, 1990-1999

Category Percent Fatal

Falling/rolling/sliding rock or material of any kind 10.69%

Explosives and breaking agents 7.92%

Electrical 3.89%

Fall of face/rib/side/highwall 2.39%

Exploding vessels under pressure 2.03%

Ignition/explosion of gas or dust 1.85%

Haulage (powered) 1.42%

Fall of roof or back 0.54%

Fire (not electrical or explosion) 0.53%

Machinery 0.44%

Not Elsewhere Classified and not an occ. illness 0.44%

Inundation 0.37%

Slip or fall of person 0.15%

Hoisting 0.13%

Hand tools 0.05%

Handling material 0.01%

Average percent fatal from all causes 0.37%

Notes: 1. Aggregated data for all mining SICs. 

 2. Categories shown produced 1or more fatalities per 10,000 

 accidents.

TABLE 2

RATIO OF MINING ACCIDENTS TO FATALITIES FROM ALL CAUSES AND FROM

ELECTRICAL CAUSES, 1990-1999

Ratio of All

Accidents to All

Fatalities

Ratio of Electrical Accidents

to

Electrical Fatalities

All Mining 272:1 26:1

Coal Operators 342:1 34:1

Coal Contractors 131:1 7:1

MNM Operators 309:1 28:1

MNM Contractors 93:1 10:1

mining methods and machines. From 1990 to 1999 MNM

operators reported 115,350 accidents, injuries and illnesses

fromall causes,including 373 fatalities. The number of active

MNM mines fell from 11,838 in 1990 to a low of 10,843 in

1996. It then increased each year to 11,821 in 1999. MNM

operator employment declined by only 7%, from 207,515 in

1990, to 192,907 in 1999. MNM contractor employment,

however,increased by69%,from26,460 in 1990 to 44,793 in

1999. LWD accidents from all causes reported by MNM

operators declined by 64%, from 7,129 cases in 1990 to

2,544 in 1999. 

Certain types of mining accidents occur infrequently but

cause a high number of fatalities per accident. Table 1 shows

types of accidents ranked by the percent that resulted in a

fatality. Mine electrical accidents are fatal in disproportion to

their frequency. They rank 3rd in the overall ratio of total

accidents to total fatalities. Many high frequency accident

types (i.e., handling materials, slips and falls, etc.) have a low

likelihood of resulting in a fatality.

Table 2 shows the accident-to-fatality ratio for each

category of employer in the mining industry. Both coal and

MNM contractors reported a higher ratio of electrical

fatalities to electrical accidents than did their respective

operators.

III. MINE ELECTRICAL INJURY DATA

Mining accident data can be sorted in many useful ways

that allow some insight into accident causes and can indicate

where specific types of solutions (engineering controls, work

place reengineering, training, etc.) might mitigate the number

and/or severity of accidents.

A. Degree of Injury for Mining Electrical Accidents

Table 3 shows the Degree of Injury (injury outcome) that

resulted fromeach of the 1,926 reported electrical accidents.

75 (3.9%) were fatalities. 58% of electrical injuriesresulted

in LWDs only and 23% resulted in an injury without death,

days away, or restricted activity. Only 4.6% resulted in no

injury.

B. Standard Industrial Classification

Electrical injuries andfatalities canbe categorized by SIC,

whichallows association of injuries andfatalitieswithspecific

commodities. Table 4 shows each mining sector that reported

more than 10 electrical injuries between 1990 and 1999.

C. The Effect of Mine Size on Electrical Injuries

Electrical injuries were examined to learn how mine size

affected their frequency. Mines that reported 1 or more

employeesfor a givenyear were separatedinto two categories

- “small” (1 to <50 employees) and “large” (50 or more

employees)forthis analysis. Approximately 75% of electrical

accidents reported all of the required information. Small

mines reported 311 (34% of) LWD electrical accidents; 25

were fatal. Large mines reported 611 (66% of) LWD

electrical accidents; 35 were fatal. Small mines reporting

electrical accidents accountedfor only 8% of the total average

annual employment during the study periodwhile large mines

employed92%. Small mines are more hazardous workplaces

than large mines for both electrical accidents and fatalities.

D. Nature of Injury

Nature of Injurydatadescribesthe specificmedical injury
3 of 8

TABLE 3

DEGREE OF INJURY FOR MINE ELECTRICAL ACCIDENTS, 1990-1999

Degree of Injury Total Cases

Fatality 75

Permanent disability (partial or total) 9

Days away from work only 1,109

Days away and restricted activity 80

Days of restricted activity only 105

Injury without death, days away, or restricted activity 441

Occupational illness 0

Fatal/nonfatal injury due to natural causes 0

Fatal/nonfatal injury - nonemployee on mine property 5

NEC (first aid only, nonchargeable death/ disability 14

No injury 88

Total 1,926

TABLE 4

MINE ELECTRICAL ACCIDENTS BY SIC, 1990-1999

SIC Sector Description Injuries Fatalities

12110 Coal, Bituminous 982 33

14220 Limestone (crushed and broken) 240 8

14410 Sand and gravel 202 7

10210 Copper ore 64 6

32410 Cement 54 1

10410 Gold (lode and placer) 50 3

14550 Clay (common) 43 2

14230 Granite (crushed and broken) 34 2

14750 Phosphate rock 28 2

14294 Traprock (crushed and broken) 22 2

14742 Potash 20 2

10310 Lead and/or zinc ore 17 1

14290 Stone (crushed and broken, NEC) 17 2

10110 Iron Ore 15 0

28191 Alumina (Mill) 13 0

14743 Trona 13 1

11110 Coal, Anthracite 12 3

Total 1,826 75

Notes: 1. Injury totals include fatalities.

 2. 100 additional injuries from SIC's that reported 10 or fewer 

 electrical injuries are not shown.

 3. All fatalities are shown.

resulting from an accident. Table 5 shows that burns of all

types are the most common form of electrical injury. These

burns, which account for 65% of nonfatal electrical injuries,

are the cause of only 7% of electrical fatalities. Electrical

shock causes 24% of electrical injuries but 93%of electrical

fatalities.

Table 6 shows nonfatal injury severity based on the Nature of

Injury for LWD electrical accidents. Nonfatal Injury severity

is measured as the average number of LWDs incurred per

LWD injury. Electrical shock, the leading cause of electrical

fatalities,ranks 9th innonfatal injuryseverity. Radiation burns

from electrical arcing, the leading cause of nonfatal electrical

injury, ranks 13th. 

E. Regular Job Titles of Electrical Accident Victims

RegularJobTitlesreporting 10 or more electrical injuries

during the 1990s and their associated fatalities are shown in

Table 7. Overall, 84% of electrical injuries and 89% of

electrical fatalities reported by Regular JobTitle are shown in

the table. 

F. Work Activities Resulting in Electrical Accidents

Table 8 shows the WorkActivitythat was being performed

whenan electrical accident occurred. Each Work Activity that

recorded 10 or more electrical injuries is shown in the table.

The activitiesshown account for 89% of electrical injuries and

85% of electrical fatalities. Maintenance/repair (electrical)

was the most hazardous electrical Work Activity, accounting

for 50%of electrical accidents and 48% of electrical fatalities

reported byWork Activity. Maintenance/repair (machinery

- not electrical) was the second most hazardous electrical

Work Activity accounting for 13% of electrical accidents and

7% of electrical fatalities.

G. Machines Involved in Electrical Accidents

Table 9 shows the Machine Types involved in mine

electrical accidents and fatalities. Machine Type was reported

for 846 electrical accidents (44% of all mine electrical

accidents) and 39 electrical fatalities (52% of all mine

electrical fatalities). 92% of electrical accidents and 95% of

the electrical fatalitiesthat reported Machine Type are shown

in Table 9. Unfortunately, for analysis purposes, the leading

Machine Type reportedwasthe Machine NEC(Not Elsewhere

Classified) category accounting for 12% of the electrical

injuries and 10% of the fatalities reporting Machine Type.

Second most reported was the Continuous miner, tunnel

borer, DOSCO categorywith6% of the electrical injuries and

8% of the fatalities.

Of the 39 fatalities reporting Machine Type, 13 involved

the categoryCrane,Derrick,Cherry picker,Boomhoist, etc.,

representing 33% of the total in this category and 17% of all

mine electrical fatalities. However, this category reported

only 5% of total mine electrical injuries reporting Machine

Type. 
4 of 8

TABLE 6

ELECTRICAL INJURY SEVERITY BY NATURE OF INJURY, 1990-1999

Nature of Injury

Average

LWD per

LWD Injury

No. of

Cases

Total

LWDs

Amputation or enucleation 179 7 1,250

Fracture, chip 86 13 1,122

Dislocation 44 2 87

Asphyxia/ strangulation/ drowning/

smoke inhalation/ suffocation

43 10 428

Sprains/strains/ruptured

disc/whiplash/torn knee cartilage 

35 23 814

Burn or scald (heat - not radiation) 34 87 2,984

Burn (electrical) 34 107 3,600

NEC 31 3 92

Electric shock, electrocution 31 263 8,054

Scratches, abrasions (superficial

wounds) 

25 6 152

Concussion - brain, cerebral 23 1 23

Multiple injuries 21 32 677

Radiation effects (burn from electrical arc

- not contact) 

21 512 10,740

Hernia, rupture 16 1 16

Contusion, bruise 11 8 87

Burn (chemical) 10 74 745

Cut/laceration/puncture/infection 8 7 57

Dust or other particles in eyes 5 1 5

Poisoning, systemic 4 5 20

Hearing loss or impairment (industrial) 3 1 3

Radiation effects (sunburn) 2 1 2

Radiation effects, not elsewhere

classified 

1 1 1

Average LWD per LWD Injury 

(All Causes)

26.6

TABLE 5

NATURE OF INJURY RESULTING FROM MINE ELECTRICAL ACCIDENTS,

1990-1999

Nature of Injury Injuries Fatalities

Radiation effects (burn from electrical arc - not

contact) 

770 3

Electric shock, electrocution 447 70

Burn (electrical) 164 0

Burn or scald (heat - not radiation) 128 2

Burn (chemical) 126 0

Multiple injuries 45 0

Sprains/strains/ruptured disc/whiplash/torn knee

cartilage 

32 0

Cut/laceration/puncture/infection 28 0

Asphyxia/strangulation/drowning/smoke

inhalation/suffocation

17 0

Fracture, chip 16 0

Contusion, bruise 11 0

Scratches, abrasions (superficial wounds) 9 0

NEC 9 0

Amputation or enucleation 7 0

Poisoning, systemic 6 0

Dust or other particles in eyes 3 0

Concussion - brain, cerebral 2 0

Dislocation 2 0

Hearing loss or impairment (industrial) 1 0

Hernia, rupture 1 0

Radiation effects, not elsewhere classified 1 0

Radiation effects (sunburn) 1 0

Total 1,826 75 

Notes 1. Injury totals include fatalities. 

Overhead power lines are a major causal factor in fatal

mine electrical accidents involving cranes and other highreaching,mobile mining equipment. Mine electrical accidents

involving overhead power lines are a disproportionately fatal

accident category within the overall electrical accident

category which, in itself, is disproportionately fatal. 

Electrical accidentsreportingPumps as the Machine Type

also showed a disproportionate number of fatalities when

compared with the number of injuries. Pumps are involved in

8% of electrical fatalities but only 2% of electrical injuries

that reported a Machine Type.

H. Accident Severity Versus Age of the Victim

A Bureau of Labor Statistics (BLS) study of nonfatal

industrial injury severity showed that increasing age is highly

correlated to increasing injury severity (average LWDs per

LWD accident). [2] Fotta analyzed this trend for the mining

industryand foundsimilar results.[3] While true for accidents

in general, not all accident categories follow this trend.

Average nonfatal injury severity for mine electrical injuries

peaks at 21LWDs per LWD injuryfor the 40-49 age group and

decreases to 20 and 13 LWDs per LWD injury for the 50-59

age groupand60+ age groups,respectively. Workers less than

20 years old average about 19 LWDs per LWD injury.

Nonfatal injurycategoriesthat dominate the LWD mining

injury total include slips and falls, handling materials, etc.

These accidents produce injury types (back injuries, strains,

sprains, contusions, etc.) that may take longer to heal with

increasing age. Electrical injuries, however, produce burns,

electrical shocks, nerve andmuscular damage to body systems

and multiple body parts, where recovery time may be less

sensitive to the victim’s age.

IV. ELECTRICAL ACCIDENT NARRATIVE ANALYSIS

A. General Observation Regarding Accident Narratives

MSHArequires a descriptive narrative to be filed for each
5 of 8

TABLE 8

WORK ACTIVITY BEING PERFORMED WHEN AN ELECTRICAL ACCIDENT

OCCURRED, 1990-1999

Work Activity Injuries Fatalities

Maintenance/repair (electrical) 907 35

Maintenance/repair (machinery - not electrical) 240 5

Handling supplies/material (not timber) -

load/unload

133 4

Inspect equipment (not maintenance/repair) 104 3

Move power cable (includes reeling) 82 3

Hand tools (not powered) 30 2

Welding and cutting 28 0

Escaping a hazard 25 0

Rerail equipment (includes replace trolley pole) 20 1

Operate surface equipment nec 19 5

Observe operations 17 1

Walking/running 15 0

Move equipment (fans/pumps, not operating

machinery)

14 1

Idle (lunch, coffee break, etc.) 13 0

Operate locomotive (air trammer) 13 0

Operate mill equipment 13 0

Hand tools (powered) 12 2

Get on/off equipment, machines, etc. 11 2

Operate continuous miner 10 0

Total 1,706 64

Notes: 1. Work Activities shown reported 10 or more injuries during 

 the reporting period.

 2. 73 fatalities reported Work Activity.

 3. 1,831 accidents reported Work Activity

 4. Injury totals include fatalities.

 

mining accident, injury, or illness reported. These narratives

varywidelyintheir information content, grammar andspelling.

Some are so brief as to be unusable for analyzing an accident

situation while others contain a significant amount of

information. In addition, MSHA subject matter experts

document each fatality with a more detailed fatality report.

Whencompleted, these fatalityreports arepublicallyavailable

on the MSHA website (http://www.msha.gov).

Capelli-Schellpfeffer recommended integrating accident

narratives with statistical information to increase the reliability

of electrical accident causal analyses. [4] That approach was

adopted for this analysis. Automatedkeywordsearches of the

MSHA database narrative information proved of significant

value in the identification of causal factors in the narratives

examined. Although some undercounting may occur,

computerized text string searches can help investigators with

subject matter familiarityrapidlykey in on important problem

areas. Care must be exercised to ensure that keywords are

used only within their relevant contexts. Therefore, reading

andmanual classification of narrativesselectedbykeywordsis

imperative. The narratives from 1,926 electrical accidents

(including75 fatal accidents) were examinedandthe frequency

of in-context relevant word usage was determined.

B. Information from Selected Electrical Accident Narratives

Several factors rapidly emerged from the analysis of

accident narratives. Circuit voltage was mentioned in only 279

of 1,926 narratives. In addition, the keywords “breaker(s)”

(313 of 1,926 narratives), “cable(s)” (309 accidents),

“batter(y)(ies)” (242 accidents), “energize(d)” (i.e., working

live) (163 accidents), “grounds/grounding” (204 accidents),

TABLE 7

REGULAR JOB TITLE OF MINING ELECTRICAL ACCIDENT VICTIMS,

1990-1999

MSHA

Code

Regular Job Title Injuries Fatalities

302 Electrician (surface) 287 14

304 Mechanic/repairman (surface) 193 4

102 Electrician (off section) 126 6

374 Cleaning plant/ media/ crusher/ 118 4

104 Mechanic/repairman (off section) 95 1

316 Laborer/utility man/pumper (surface) 87 3

116 Laborer/muck machine operator/pipe 58 2

50 Shuttle car operator/ram car (on 53 2

449 Mine foreman/mine manager/owner 47 2

2 Electrician (on section/face) 46 2

494 Prep plant foreman/mill foreman 46 3

376 Truck driver (surface) 42 3

46 Roof bolter/rock bolter (on 40 0

149 Labor foreman/bullgang foreman (off 38 1

418 Maintenance foreman (supv/staff) 34 3

368 Bulldozer operator/ tractor/ heavy 33 1

382 Highlift/ front end loader operator 33 0

481 Superintendent (supv/staff) 33 2

489 Outside foreman (supv/staff) 33 3

319 Welder (surface) 25 2

4 Mechanic/repairman (on section/face) 24 3

269 Motorman/ swamper/ switchman (UG 21 0

36 Continuous miner operator/ mole (on 18 0

101 Belt/conveyor man (off section) 18 0

402 Master electrician (supv/staff) 18 3

456 Engineer - EE/ ventilation/ mining 15 1

318 Oiler/greaser (surface) 12 0

54 Scoop car/unitrac operator (on 11 1

301 Belt/conveyor man (surface) 11 0

372 Barge/boat/dredge attendant (surface) 11 1

Total 1,626 67

Notes: 1. Regular Job Title shown for each RJT reporting 10 

or more electrical accidents during the period. 

 2. 71 fatalities reported Regular Job Title.

 3. 1,801 accidents reported Regular Job Title

 4. Injury totals include fatalities
6 of 8

TABLE 9

MACHINE TYPES INVOLVED IN MINE ELECTRICAL ACCIDENTS, 1990-1999

Machine Injuries Fatalities

Machine, NEC (Not Elsewhere Classified) 99 4

Continuous miner, tunnel borer, DOSCO 53 3

Mancar, mantrip, personnel carrier, portabus,

jeep, jitney

49 1

Front-end loader, payloader, highlift, etc. 47 0

Hand tools (not powered) - wrench, jacks, etc. 46 1

Welding machine, bonder, torch 45 1

Shuttle car - buggy, torkar, ram car 43 2

Crane, derrick, cherry picker, boom hoist, etc. 42 13

Ore haulage trucks - off highway and

underground

38 2

Conveyor, belt feeder, mobile bridge carrier,

ROSCO

34 2

Locomotive, rail-mounted, lorry car 34 0

Rock or roof bolting machine 34 0

Crusher, breaker, mills (ball and rod) 31 0

Shovel or dragline (mining and stripping) 29 2

Load-haul-dump/ scoop tram/ CAVO/

transloader/ ram car

28 0

Bulldozer, dozer, crawler tractor, etc. 19 0

Trucks - pickup/dump/water/service (not ore

haulage)

19 0

Drills (electric/hydraulic/coal - not impact drills) 18 0

Fan 16 0

Pump 16 3

Milling machinery, nec 15 1

Hand tools (powered) - drill, impact wrench, etc. 14 2

Drill (carriage-mounted) on track/rail/rubber tired 10 0

Total 779 37

Notes: 1. Machine Types shown reported 10 or more injuries 

 during the reporting period.

2. 39 fatalities reported Machine Type.

3. 846 accidents reported Machine Type

4. Injury totals include fatalities.

andelectrical “meter(s)” (90 accidents) were involvedinabout

two-thirds of mine electrical accidents. A total of 1,321

narratives containing these six keywords were analyzed and

their causal factors determined. 

1. Circuit voltage: The circuit voltage is specifically

mentioned in only 279 (14%) of all mine electrical accident

narratives, limiting its usefulness in determining possible

accident mitigation strategies. 57% of the 243 alternating

current accidents occurred at or below 600Vac, 3% between

601 and 1000Vac and 40% at more than 1000Vac. Accidents

involving DC circuits mention specific voltages in only 36

cases, covering the range from common battery voltages to

trolley circuit voltages (6Vdc to 750Vdc). The reliability of

voltage data in accident narratives could be improvedbyalways

reporting the nominal circuit voltage of an electrical accident

and by specifying whether the accident occurred via phase-tophase or phase-to-ground contact.

2. Circuit breakers: 313 circuit “breaker” accidents were

grouped into 8 causal categories:

• electrical maintenance or repair working live (either

intentionally or unintentionally) - 125 cases;

• operating/resetting a circuit breaker - 108 cases;

• equipment failure - 22 cases;

• shocked /burned while plugging/unplugging connectors -

15 cases;

• working in proximity to a live circuit - 15 cases;

• energized/de-energize the wrong circuit breaker - 14

cases;

• unknown cause - 8 cases, and;

• misclassified - 6 cases.

3. Cables: 309 cable accidents were grouped into 10 causal

categories:

• handling or moving live cable, plugs,or running over live

cable - 86 cases;

• jumper cables and batteries - 65 cases;

• electrical maintenance or repair working live (either

intentionally or unintentionally) and plugging/unplugging

live connectors, - 59 cases;

• shocked or burned unexpectedly - 31cases;

• equipment failure (cause unknown) - 27 cases;

• power-off electrical repair accident (energizing cable

after repair, working in proximity to live circuits) - 12

cases;

• touching bad splices - 12 cases;

• contact with overhead power lines - 11 cases;

• unclassifiable - 4 cases, and;

• misclassified accidents - 2 cases.

Only12 accidents mentioned that aworker contacted a bad

cable splice while 86 accidents involved workers handling

cables containing previously unknown cuts and abrasions that

apparently exposed live conductors. 

4. Batteries: 242 battery accidents were grouped into 8 causal

categories:

• battery exploded during or immediately after

maintenance or repair - 110 cases;

• while using jumper cables, battery exploded - 46 cases;

• battery exploded while charging battery or plugging or

unplugging charger cable - 28 cases;

• other cables arced or exploded during maintenance - 15

cases;

• battery exploded spontaneously - 15 cases;

• jumper cables arced or exploded during use - 5 cases;

• other - 21 cases, and;

• misclassified - 2 cases.
7 of 8

5. Grounding: Of the 204 accidents containing the text string

“ground.”, only 129 represented cases that were not either

double-counted from another keyword category or truly

represented a grounding problem. These 129 grounding

accidents were grouped into 9 causal categories:

• failure to de-energize equipment (intentionally or

unintentionally) prior to grounding work - 47 cases;

• grounding system, component, or insulation defects in

stationary equipment - 29 cases;

• using grounding test equipment, meters, leads - 13 cases;

• grounding defects in mobile equipment - 13 cases;

• ground conductor defects - 12 cases;

• grounding defects in portable cords - 3 cases;

• unknown causes - 8 cases, and;

• welding - 4 cases.

6. Working on energized circuits: 163 accidents occurred

while working on energized electrical circuits. Injuries

resulting from working on energized electrical circuits were

grouped into 9 causal categories:

• knowingly failed to de-energize the circuit before

beginning work - 78 cases;

• equipment failure (includes cut and abraded cables) - 37

cases;

• de-energized the wrong circuit or did not de-energize

adjacent circuits - 16 cases;

• working under or near energized trolley line - 9 cases;

• using improper tools/equipment/test leads or improper

use of same - 8 cases;

• circuit reenergized by another person during work - 6

cases;

• working under or near energized power line - 4 cases;

• improper cable repair (leads reversed) - 1 case, and;

• unknown cause - 4 cases.

7. Using meters and test leads for troubleshooting: 90

accident narrativesmentionedthat the victimwas using ameter

to troubleshoot an electrical circuit. Injuries resulting from

using meters on energized electrical circuits were grouped

into 8 causal categories:

• meter exploded (cause unspecified) - 30 cases;

• test leads/probes shorted, arced - 21 cases;

• meter used on wrong function (e.g., measured volts on

ohms scale) - 13 cases;

• meter of wrong voltage used (e.g., used a 1000V meter

on a 4160V circuit) - 10 cases;

• dropped / misused meter - 8 cases;

• victim wearing metal jewelry - 1 case;

• unknown cause - 4 cases, and;

• misclassified - 3 cases.

V. IMPLICATIONS FOR MINE ELECTRICAL RESEARCH

Rossignol points out that while training solutions are often

suggestedfor electrical hazards,interventioneffortsmustshift

toward engineering control solutions “to reduce the hazard at

its source”. [5] This is practical in many situations. Simple,

cost effective engineering control solutions exist to reduce

fatalities and mitigate severity of nonfatal electrical injuries.

Manuele notes that 60% of identified barriers to safe work

behaviors arise fromshortcomings in facilities and equipment

and 13% from management systems. [6] “That suggests,” he

contends, “that the greatest risk reduction will come from

attention to those two subjects”. While suitable kinds and

levels of training cannot be overlooked, over dependance on

training at the expense of engineering control interventions,

where appropriate, is a serious error. 

Safety strategies common to many electrical accident

prevention programs include:

1. working live only as a last resort; 

2. training in the use of proper lockout-tagout procedures;

3. training in the use of appropriate PPE, including:

a. UV limiting eye or full-face protection;

b. lightweight, fire-retardant work clothes for

electrical maintenance personnel and arc protection

suits where needed, and;

c. the use of dryelectrical gloves, insulating blankets,

and other situation specific PPE as needed.

A. Mitigating the Frequency and Severity of Flash Burn

Injuries

“Radiationeffects (burnfromelectrical arc)” type injuries

caused40% of all mining electrical injuries and accountedfor

34% of electrical LWDs. Such injuries are largely a

consequence of working live andaccount for a high percentage

of electrical eye and hand injuries. Only 3 fatalities were

directly attributed to this Nature of Injury. 

Possible mitigationsfor electrical arcburninjuriesinclude

limiting the available arc blast energy, therefore injury

severity, by using current limiting circuit protection,

eliminating or reducing intentional time delays in protective

devices and using high resistance grounding where practical.

B. Mitigating the Frequency and Severity of Electrical

Shock Injuries

“Electrical shock, electrocution” injuries caused 23% of all

mine electrical injuries and accounted for 26% of electrical

LWDs. Such injuries are often the consequence of working

live or in proximity to unguarded live conductors. They

account for 63%ofthe LWDs attributedto “body systems” and

“multiple body parts” from electrical injuries. In addition,

93% of mine electrical fatalities were attributedto “electrical

shock, electrocution”. Possible mitigations for electrical

shock/ electrocution injuries include the increased use of

ground fault circuit interrupters (GFCIs), maintaining the
8 of 8

proper clearance when working near overhead electric power

lines, the use of insulating load link devices and the use of

power line proximity and/or contact warning systems.

C. Mitigating the Frequency and Severity of Electrical

Injuries in Maintenance Work Activities

TheWork Activity “maintenance / repair- electrical” caused

50% of nonfatal mine electrical accidents and 48% of the

fatalities reported by Work Activity. The Work Activity

“maintenance / repair- machinery” caused 13% of nonfatal

mine electrical accidents and 7% of fatalities. Collectively

“maintenance / repair - ....” represents 60% of all electrical

accidents and 53% of all electrical fatalities. Obviously

electrical maintenance is a hazardous WorkActivitydeserving

special attention.

Possible mitigations for maintenance worker electrical

injuriesinclude the increased applicationof GFCIs andthe use

of “dead-front” type equipment to isolate maintenance

personnel from electrical hazards during troubleshooting.

Overall,the safety of electrical maintenance workers could be

improved by requiring that each electrical enclosure have a

singledisconnectmechanismorinterlockthat de-energizedall

circuits within an enclosure. This could reduce accidents

caused by unintentional contact with adjacent circuits thought

to be de-energized or locked-out.

Electrical maintenance/repair workers frequently use

metersto troubleshootlive electrical circuits. Examination of

accident narratives shows a need for an improved method of

accurately verifying meter capabilities and functions in the

field to avoid using meters of improper voltage rating or

meters set to measure the wrong function.

Suggestions for improvingthe safe useof electrical meters

during live troubleshooting procedures include:

1. color coding or clearly marking meters with their

maximum safe voltage and/or current ratings;alternatively,

using only single function meters that are color coded or

clearly indicate their function(e.g.,voltage, current, ohms,

etc.). The use of multifunction meters makesit easier for

workers to use the wrong meter function or scale;

2. using meters that autorange up to their maximum voltage

and/or current to prevent range selection problems;

3. using test leads rated for the maximum voltage and/or

current of the associated meter, and;

4. using safety test leads with minimal tip exposure to

preclude accidental contact with adjacent circuits, not

uninsulated or oversized alligator clips.

VI. SUMMARY

Electrical accidents are the 4th leading cause of death in

mining and are disproportionately fatal compared with most

other types of mining accidents. It can be argued that every

electrical accident is a potential fatality except for some

serendipitous set of circumstancesthat combine to prevent the

victim’s death.

About one-half of all mine electrical injuries and fatalities

occur during electrical maintenance work. Injury severity

(average LWDs per LWD accident) increases with age for

mining accidentsfromall causes, but decreases after age 40-

49 for mine electrical accident victims. Burns are the leading

cause of electrical injuries by a nearly 2-to-1 margin, but

electrical shock caused 93% of all mine electrical fatalities.

On average, nonfatal electrical shock injuries were more

severe (31 LWDs/LWD injury) than nonfatal burninjuries(21

LWDs/LWD injury). Small mines may be more electrically

hazardous workplacesthan large mines basedon total average

employment.

Analyzingaccident narratives using computerizedkeyword

searches allows rapid identification of core problem areas.

Core areas so identified involve “breaker(s)” (313 of 1,926

accidents), “cable(s)” (309 accidents), “batter(y)(ies)” (242

accidents), “energize(d)” (i.e., working live) (163 accidents),

“grounds/grounding”(204 accidents), and electrical “meter(s)”

(90 accidents). 

Improvedsystemdesign, improvedelectrical maintenance

procedures andschedules,useof powerline avoidancedevices,

power line awareness training, training targeted at known

problem areas and vigorous electrical enforcement can

combine to improve electrical safety substantially. 

REFERENCES

[1] Title 30, Code of Federal Regulations (CFR) §50.2, (h)(1-12), available at

the website: http://www.msha.gov/regdata/msha/50.2.htm

[2] Bureau of Labor Statistics, U.S. Department of Labor, “Older workers’

injuries entail lengthy absences from work”, Summary 96-6, April 1996.

[3] Fotta, Barbara, G. Bockosh, NIOSH Pittsburgh Research Laboratory,

CDC, U.S. Department of Health and Human Services, “The aging

workforce: an emerging issue in the mining industry”, 2000, 13 pp., in

press.

[4] Capelli-Schellpfeffer, Mary, Floyd, II, L., Eastwood, K., Liggett, D.,

“How we can better learn from electrical accidents”, IEEE IAS

Magazine, May/June 2000, pp. 16-23.

[5] Rossignol, M., M. Pineault, “Classification of fatal occupational

electrocutions”, Canadian Journal of Public Health., Vol. 85, No. 5,

Sept-Oct. 1994, pp. 322-325. 

[6] Manuele, Fred A., “Behavioral safety: looking beyond the worker”, 

Occupational Hazards, October 2000, pp. 86-88.