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Electrical Hazards

Electrical Hazards

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Electrical Hazards

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  1. Electrical Hazards • Electrical accidents in the mining industry are caused by: 1. Failure to lockout/tag electrical equipment 2. Unqualified people doing electrical work 3. Contact with overhead powerlines 4. Improper installation and maintenance

  2. Consequences of electrical accidents • Fires and Explosions • Burns • Shock/Electrocution

  3. Fires and Explosion We can prevent fires and explosions by: • Preventing overcurrent conditions such as short circuit or overload and using proper protection for circuits and equipment; * using installation methods to protect conductors and equipment from damage or contact that might result in an arc or overcurrent condition or shock; and * using equipment designed to prevent arcing during normal operation which could cause an explosion.

  4. Burns • Electrical arcs produce tremendous amounts of heat. We can attest to this from the use of electrical arcs for welding metals. The temperature of an electric arc at currents of 2-20 Amps can range from 3600 to 7200 degrees at the starting and ending points of the arc.

  5. The heat from normal arcing causes some destruction of equipment components such as contacts, commutators, etc. Periodic maintenance is necessary to take care of these losses.

  6. Shocks and Electrocutions • There are several factors that can be detrimental during electrical shock. These factors include, but are not limited to: Amount of current Time exposed and, Current path through the body Let’s look at Ohm’s Law

  7. EFFECTSOF CURRENT ON THE AVERAGE BODY

  8. How much current does it take to illuminate this 60 watt, 120 volt light bulb? • The answer is 0.5 amperes or 500 milliamps. • Did you know that this is five times the current that it takes to fatally electrocute someone ? 60 WATT 120 VOLTS

  9. CURRENT EFFECT 1 MILLIAMP THRESHOLD OF PERCEPTION 1 TO 8 MILLIAMPS SENSATION OF SHOCK 8 TO 15 MILLIAMPS PAINFUL SHOCK 15 TO 20 MILLIAMPS LOSS OF MUSCLE CONTROL

  10. 20 TO 50 MILLIAMPS BREATHING IS DIFFICULT 100 TO 200 MILLIAMPS VENTRICULAR FIBRILLATION OVER 200 MILLIAMPS SEVERE BURNS

  11. GFCI

  12. sound

  13. On August 17, 2002, a 31-year-old contract miner with 4 years of experience was fatally injured in a tunnel construction project at an open pit copper mine. A transformer switch, mounted on a rail car, was being moved forward as construction advanced. The victim was electrocuted when he contacted a 480 volt cable and a junction box to move them from rubbing the rail car. The cable and junction box were part of the lighting system located along the side of the tunnel. report

  14. CONCLUSION The cause of the accident was the failure to provide an effective low impedance grounding circuit for the tunnel lighting system. The following root causes were identified: failure to properly assemble the light fixture; failure to properly test the light fixture and failure to properly test the resistance of the light circuit ground system.

  15. Citation No. 6273824 was issued on August 18, 2002, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 57.12001: • On August 17, 2002, a fatal accident occurred at this mine when a contract miner contacted an energized 480/277 volt cable attached to a metal light assembly. The tunnel lighting system/circuit was not protected against excessive overload with fuses or circuit breakers of the correct types and capacity. Failure to ensure that the circuit overload protection was properly installed and maintained constitutes more than ordinary negligence and is an unwarrantable failure to comply with a mandatory standard.

  16. Order No. 6273825 was issued on August 18, 2002, under the provisions of Section 104(d)(1) of the Mine Act for violation of 30 CFR 57.12025: • On August 17, 2002, a fatal accident occurred at this mine when a contract miner contacted an energized 480/277 volt lighting circuit attached to a metal light assembly. The metal frame of the light assembly was energized in excess of 150 volts, phase-to-ground. The metal enclosing and incasing electrical circuit was not effectively grounded or provided with effective equivalent protection. Excessive impedance of the primary and secondary equipment grounding circuit did not provide for sufficient current flow to open the provided protection. Failure to ensure that effective grounding was provided for the circuit, constitutes more than ordinary negligence and is an unwarrantable failure to comply with a mandatory standard.

  17. report On October 2, 2001, a contract electrician was fatally injured at a sandstone operation. The victim had been installing power lines to an elevated electrical box mounted on the side of a building. As he swung the manlift he was working from away from the building he contacted high voltage power lines that were located above his work area.

  18. 104(a) Citation for violation of 56.12071: • A fatal accident occurred at this operation on October 2, 2001, when a contract electrician in a JLG manlift basket, contacted energized overhead high voltage power lines. The manlift being used had the reach capacity to contact overhead power lines yet the lines were not de-energized nor were other precautionary measures taken to protect persons. 30 CFR § 56.12071 Movement or operation of equipment near high-voltage power lines. When equipment must be moved or operated near energized high-voltage powerlines (other than trolley lines) and the clearance is less than 10 feet, the lines shall be deenergized or other precautionary measures shall be taken.

  19. On September 16, 2002, a 42 year-old welder with 2 years mining experience was fatally injured at a crushed stone operation. The victim was lying on a wet, metal screen deck welding a wear plate in a confined area when he apparently touched the energized welding rod to his chest and received an electrical shock. report

  20. The cause of the accident was the victim contacting the energized welding electrode. The root causes were the failure to utilize dry insulating material while welding when lying on steel, and failure to wear dry clothing. No citations issued

  21. On Tuesday, March 13, 2001, an electrical contractor, with 16 years of experience, was fatally injured when he contacted high voltage power while installing pole mounted capacitors. The victim and two co-workers had completed the installation of the capacitors, located approximately 900 feet from the mine substation, and installed a size 14 twisted pair wire from the substation to the capacitors to provide 120 volt control power for a capacitor switching device. The victim, two co-workers and three mine employees, were standing at the mine substation when the plug for the twisted pair wire began to smoke and arc. The victim, pulled the plug from the receptacle, picked up the plug to examine it and received a fatal electrical shock. A phase imbalance was caused when a defective switch on one of the capacitors failed to close and induced a current flow onto the frame of the capacitors and the ground wire extending down the pole to a ground rod. The frames were common with the neutral wire of the size 14 control power conductor. When the victim contacted the neutral wire, he became a parallel path for this current flow. report

  22. A 104(a) Citation was issued to the operator for a violation of 77.502. The citation stated, "It was determined that electric equipment involved in the accident was not properly examined, tested and maintained by a qualified person to assure safe operating conditions. The following dangerous conditions were found to exist: (1) One of the three oil switches used to control the capacitors was not working properly. The electrical contact tips were worn and not making proper contact. Bolts that held the switching mechanism in place were missing or loose. The oil inside the switch was contaminated. (2) The capacitors were not installed according to manufacturers recommendations. (3) The resistance of the capacitor frame ground was too high to provide a proper low resistance grounding medium. (4) A 14/2 TW twisted pair telephone wire, without ground conductor, was used to supply 120 volt control power. (5) Control power for capacitor bank location, this would reduce transfer of voltage potentials. This condition contributed to the accident that occurred on March 13, 2001.

  23. A 104(a) Citation was issued to the contractor for a violation of 77.502. The citation stated, "It was determined that electric equipment involved in the accident was not properly examined, tested and maintained by a qualified person to assure safe operating conditions. The following dangerous conditions were found to exist: (1) One of the three oil switches used to control the capacitors was not working properly. The electrical contact tips were worn and not making proper contact. Bolts that held the switching mechanism in place were missing or loose. The oil inside the switch was contaminated. (2) The capacitors were not installed according to manufacturers recommendations. (3) The resistance of the capacitor frame ground was too high to provide a proper low resistance grounding medium. (4) A 14/2 TW twisted pair telephone wire, without ground conductor, was used to supply 120 volt control power. (5) Control power for capacitor switching was not derived at the capacitor bank location, this would reduce transfer of voltage potentials. This condition contributed to the accident that occurred on March 13, 2001."

  24. 30 CFR § 77.502 Electric equipment shall be frequently examined, tested, and properly maintained by a qualified person to assure safe operating conditions. When a potentially dangerous condition is found on electric equipment, such equipment shall be removed from service until such condition is corrected. A record of such examinations shall be kept. POLICY 77.502 Electric Equipment; Examination, Testing and MaintenanceFor purposes of this Section, "electric equipment" shall include all control circuits; control switches or devices; circuit breakers; fuses; conduits; wiring; motors; transformers; lighting equipment; hand-held tools such as drills, wrenches, and saws;etc. The tests, examinations, and proper maintenance required by this Section shall include all items mentioned above and all other such equipment at the mine.

  25. A 104(a) Citation was issued to the operator for a violation of 77.501. The citation stated, "It was determined that electrical work was performed by persons who were not qualified or were not under the direct supervision of a qualified person as provided by 77.103. The following electrical work was performed: (1) A 120 volt control circuit was installed with wiring connection made inside a junction box and plug end installed. (2) Splices were made in the 120 volt control wire. (3) Installation of capacitors and connection to the 12,470 volt power conductors. (4) Lock and tag out. (5) Installation of grounding conductors. This condition contributed to the accident that occurred on March 13, 2001.

  26. A 104(a) Citation was issued to the contractor for a violation of 77.501. The citation stated, "It was determined that electrical work was performed by persons who were not qualified or were not under the direct supervision of a qualified person as provided by 77.103. The following electrical work was performed: (1) A 120 volt control circuit was installed with wiring connection made inside a junction box and plug end installed. (2) Splices were made in the 120 volt control wire. (3) Installation of capacitors and connection to the 12,470 volt power conductors. (4) Lock and tag out. (5) Installation of grounding conductors. This condition contributed to the accident that occurred on March 13, 2001."

  27. 30 CFR § 77.501 No electrical work shall be performed on electric distribution circuits or equipment, except by a qualified person or by a person trained to perform electrical work and to maintain electrical equipment under the direct supervision of a qualified person. Disconnecting devices shall be locked out and suitably tagged by the persons who perform such work, except that in cases where locking out is not possible, such devices shall be opened and suitably tagged by such persons. Locks or tags shall be removed only by the persons who installed them or, if such persons are unavailable, by persons authorized by the operator or his agent. POLICY "Electrical work," as referred to in this Section, includes the design, installation, maintenance or repair of electric equipment and circuits. Splices and terminations made in electric cables, installation of couplers on the ends of cables, electric machine repairs, electric wiring, pole and line work, work performed inside electrical substations or other areas in proximity to exposed energized electrical parts, work performed inside transformers, switchboxes, switch houses, electric panels or other enclosures of electric equipment and circuits are examples of tasks that are considered to be "electrical work" and are required to be performed by or under the direct supervision of a qualified person.

  28. POLICY 77.501 • Examples of duties that are not considered to be "electrical work" and would not be required to be performed by a qualified person or under the direct supervision of a qualified person are, operation of electric equipment, transportation of equipment and cables, operation of control switches, circuit breakers or switchboxes, provided no energized parts are exposed, changing cutting bits, lubrication work, moving of energized trailing cables, or inserting or withdrawing proper cable couplers into or from their receptacles. These tasks are considered to be part of the normal routine operation of electric equipment; therefore, they are not considered to be "electrical work." • The term "direct supervision" shall not be interpreted to mean that the qualified person be physically present at all times during the performance of such repairs, but the qualified person has the following responsibilities: • 1.The qualified person shall examine and/or test an electric circuit or machine and determine the need for repair or maintenance.2.The qualified person must give specific instructions to the employee assigned to perform this work with respect to the nature and extent of the repairs to be performed and, where necessary, prescribe the manner in which the work is to be performed.3.The qualified person is, at all times, under continuing duty to instruct, advise, or consult with the employee, in the event the work assigned cannot be performed by the employee in the manner prescribed.

  29. POLICY 77.501 • 4.The qualified person must examine and test the completed work before the circuit is energized or the machine is returned to service. • It is MSHA's policy that a person trained to perform electrical work and to maintain electric equipment under the direct supervision of a qualified person shall not be assigned the duty of testing or troubleshooting energized circuits. Persons trained to perform electrical work and to maintain electric equipment may only do testing and troubleshooting on energized circuits as part of their training program. During this testing and troubleshooting operation, a qualified person, as defined in Section 77.103, must be present at all times to observe,instruct, and aid the trainee. • "Suitably tagged" means that a sign with wording such as"Danger - Hands Off - Do Not Close - Miners Working on Line,"shall be attached to the opened disconnecting device. The tag should bear the name of the workman who installed it. • Keys to locks used to lock out switches should be kept by the person working on the circuit or equipment

  30. A 104(a) Citation was issued to the operator for a violation of 77.516. The citation stated, "It was determined that improper wiring methods were used to supply the 120 volt control power for the capacitor switching circuit. A 14/2 TW twisted pair telephone wire, without ground conductor, was used. A 120 volt three-prong plug was installed on the 14/2 wire and plugged into a ground fault circuit interrupter outlet at the mine substation. The 14/2 wire ran for 733 feet along the highwall, lying on the ground, and suspended on trees at some locations to the pole mounted capacitors. Splices were made in the 14/2 wire. The capacitor manufacturer recommends control power be derived at the capacitor bank location. Reference the following articles of the 1968 National Electrical Code: 250-59 which requires a grounding conductor to be run with the power supply conductors; 300-4 which provides for protection against damage; 310-1(a) which requires that conductors have mechanical strength, insulation, and ampacity adequate for the conditions; 400-4 which prohibits use of cords for this application; and 400-5 which requires cords to be used in continuous lengths without splices. This condition contributed to the accident that occurred on March 13, 2001

  31. A 104(a) Citation was issued to the contractor for a violation of 77.516. The citation stated, "It was determined that improper wiring methods were used to supply the 120 volt control power for the capacitor switching circuit. A 14/2 TW twisted pair telephone wire, without ground conductor, was used. A 120 volt three-prong plug was installed on the 14/2 wire and plugged into a ground fault circuit interrupter outlet at the mine substation. The 14/2 wire ran for 733 feet along the highwall, lying on the ground, and suspended on trees at some locations to the pole mounted capacitors. Splices were made in the 14/2 wire. The capacitor manufacturer recommends control power be derived at the capacitor bank location. Reference the following articles of the 1968 National Electrical Code: 250-59 which requires a grounding conductor to be run with the power supply conductors; 300-4 which provides for protection against damage; 310-1(a) which requires that conductors have mechanical strength, insulation, and ampacity adequate for the conditions; 400-4 which prohibits use of cords for this application; and 400-5 which requires cords to be used in continuous lengths without splices. This condition contributed to the accident that occurred on March 13, 2001."

  32. 30 CFR § 77.516 In addition to the requirements of §§77.503 and 77.506, all wiring and electrical equipment installed after June 30, 1971, shall meet the requirements of the National Electric Code in effect at the time of installation. POLICY Section 77.516 requires, in addition to compliance with Sections77.503 and 77.506, that electric equipment installed after June 30, 1971, meet the requirements of the NEC. The NEC has been incorporated into MSHA standards to address wiring and wiring methods for surface facilities and structures not specifically covered in Part 77. The NEC will continue to be applied to surface facilities and structures other than the specified excavation equipment. The NEC contains safety guidelines which are not specifically tailored to surface mine excavation equipment and conductors, but which cover a much broader scope. While Section 77.516 addresses wiring and electric equipment installed after June 30, 1971, on surface mining machines, many provisions of the NEC are not applicable to the wiring methods, types of equipment, and conditions on these machines. For example, certain excavation equipment designed and installed since June 30, 1971, is not compatible with the requirements of the 1968 NEC. Therefore, strict application of and compliance with the NEC for the wiring methods used on surface mine excavation equipment is not practicable.

  33. Wiring and electric equipment installed after June 30, 1971, on-board electric or diesel-powered surface excavation equipment are not required to comply with the NEC under Section 77.516,although mine operators are free to rely on it as a guideline.This policy applies to equipment such as draglines, shovels, dozers, bucket wheel excavators, mobile drills, mobile cranes,haulage trucks, and endloaders. However, all other relevant provisions in Part 77 will continue to apply to these machines.Equipment and wiring installed after June 30, 1971, will be inspected and enforcement action taken in the same manner as on equipment installed prior to that date. For example, Sections77.404 and 77.502 requiring examination and proper maintenance will be enforced, along with appropriate conductor ampacities under Section 77.503, short-circuit and overload protection under Section 77.506 and all relevant grounding provisions.

  34. A 104(a) Citation was issued to the operator for a violation of 77.701. The citation stated, "It was determined that the metallic frame of the capacitor bank was not properly grounded to a low- resistance ground field. A copper rod was driven into the ground at the base of the pole (butt ground) to create a ground/neutral point for the capacitor installation. The value of the butt ground was measured and found to be 195 ohms. Regulation requires that the grounding conductor extend to a low-resistance ground field. This condition contributed to the accident that occurred on March 13, 2001

  35. A 104(a) Citation was issued to the contractor for a violation of 77.701. The citation stated, "It was determined that the metallic frame of the capacitor bank was not properly grounded to a low- resistance ground field. A copper rod was driven into the ground at the base of the pole (butt ground) to create a ground/neutral point for the capacitor installation. The value of the butt ground was measured and found to be 195 ohms. Regulation requires that the grounding conductor extend to a low-resistance ground field. This condition contributed to the accident that occurred on March 13, 2001."

  36. 30 CFR § 77.701 Metallic frames, casings, and other enclosures of electric equipment that can become "alive" through failure of insulation or by contact with energized parts shall be grounded by methods approved by an authorized representative of the Secretary. POLICY Certain moveable electric equipment, e.g., rail-mounted and pivoting coal stackers, traveling shop cranes on track rails, small traveling hoists on I beams, etc., cannot be strictly classified as portable, mobile or stationary equipment. For the purposes of frame grounding, such equipment shall be considered stationary. Consequently, the grounding requirements of Subpart H apply to such equipment. This Section requires that metallic frames of electric equipment be grounded by methods approved by an authorized representative of the Secretary. Therefore, rail-mounted and pivoting coal stackers, traveling shop cranes on track rails, small traveling hoists on I beams, and similar equipment shall be grounded in accordance with the following:

  37. A 104(a) Citation was issued to the operator for a violation of 77.1710(c). The citation stated, "It was determined that the victim was not wearing protective gloves when he pulled the 120 volt control power plug from the receptacle and then picked up the plug. The plug was arcing and smoking. The victim received a fatal electrical shock as power fed back on the control wire from the capacitor bank. This condition contributed to the accident that occurred on March 13, 2001

  38. A 104(a) Citation was issued to the contractor for a violation of 77.1710(c). The citation stated, "It was determined that the victim was not wearing protective gloves when he pulled the 120 volt control power plug from the receptacle and picked up the plug. The plug was arcing and smoking. The victim received a fatal electrical shock as power fed back on the control wire from the capacitor bank. This condition contributed to the accident that occurred on March 13, 2001."

  39. 30 CFR § 77.1710 Each employee working in a surface coal mine or in the surface work areas of an underground coal mine shall be required to wear protective clothing and devices as indicated below: (c) Protective gloves when handling materials or performing work which might cause injury to the hands; however, gloves shall not be worn where they would create a greater hazard by becoming entangled in the moving parts of equipment. POLICY Paragraph (c) of this Section requires that miners wear gloves whenever they troubleshoot or test energized electric power circuits or electric equipment. Work gloves in good condition are acceptable for troubleshooting or testing energized low- and medium-voltage circuits or equipment. High-voltage gloves, rated at least for the voltage of the circuit, are required for troubleshooting or testing of energized high-voltage circuits or in compartments containing exposed energized high-voltage circuits.

  40. On Friday, July 20, 2001, a 26 year old electrician, with 5 years mining experience, was fatally injured in an electrical accident. The victim was preparing to move an electrical starter box, which provided power to the No. 9 belt conveyor head drive. Apparently, the victim came in contact with the energized electrical circuit providing power to the starter box or other associated electricalequipment.

  41. 104(d)(1) Citation - Work was performed on electrical circuits and equipment without all power first being deenergized, while under the direct supervision of the chief electrician. The electrical circuit (277 volts) entering the # 9 belt starting box and supplying power to the 20 HP booster pump was not deenergized prior to work being performed on the energized circuit.

  42. 104(d)(1) Order - The 010 MMU section's 20 HP booster pump located outby the # 9 belt drive was not grounded as required. A separate circuit originating from the booster pump starter had been installed to the # 9 belt box. The start/stop switch had been defeated (by-passed). This circuit permitted the pump to start when the # 9 belt started. Power was supplied to the circuit by the 16/3 pump cable conductor. The ground wire had been cut off at both ends where the cable left the pump starter and where the cable entered the belt box. With the # 9 belt box disconnect device unplugged, the # 9 belt box was still energized with 480 volts from the 20 HP booster pump and had no means of proper grounding.

  43. 104(d)(1) Order- Mine management failed to insure that all electrical circuits and equipment were properly locked out and suitably tagged while electrical work was being performed. The electrical circuit serving the 20 HP booster pump was not locked out and suitably tagged while electrical work was being performed.

  44. 104(d)(1) Order- Electrical equipment (20 HP booster pump and the # 9 belt drive's starting box) had not been properly examined and maintained to assure safe operating condition. An examination of this equipment revealed the following conditions : 1) A separate circuit originating from the booster pump's start box had been wired to the # 9 belt box; 2) The start/stop switch located on the booster pump had been defeated (by-passed), allowing the booster pump to start when the # 9 conveyor belt was started; 3) The ground wires were found to have been cut at the booster pump and the belt drive starting box; and 4) The 20 HP booster pump was not listed in the records of the examination of electrical equipment. 30 CFR § 75.512 All electric equipment shall be frequently examined, tested, and properly maintained by a qualified person to assure safe operating conditions. When a potentially dangerous condition is found on electric equipment, such equipment shall be removed from service until such condition is corrected. A record of such examinations shall be kept and made available to an authorized representative of the Secretary and to the miners in such mine.

  45. 104(a) Citation - The site of an accident that resulted in the death of a mine electrician on July 20, 2001, was found to have been altered prior to the completion of all investigations, and without MSHA approval. It was determined that the site was altered due to the following: 1) The disconnect device (cat-head) which supplied power to the 20 HP booster pump had been disconnected at the 300 KVA power center and was lying on the mine floor; 2) The 16/3 cable extending from the booster pump to the # 9 belt drive starting box had been cut at the pump start box location; and 3) The 16/3 cable extending from the booster pump to the # 9 belt drive starting box had been disconnected from the inter lock on the vacuum breaker and had been pulled completely out of the belt box. None of these conditions could have existed at the time of the fatal accident. Mine management failed to preserve and secure the accident site. PART 50 VIOLATION

  46. 104(d)(1) Order - The electrical circuit breaker supplying power to the 20 HP booster pump located outby the # 9 conveyor belt drive was not properly marked for identification. The subject electrical circuit breaker was identified and labeled as "pump", but was in fact supplying electrical power for two different devices; the pump and a separate circuit entering the # 9 belt starting box. 30 CFR § 75.904 Circuit breakers shall be marked for identification POLICY 75.904 Identification of Circuit BreakersEither metal or plastic tags or markers may be used to identify circuit breakers if the tags or markers are attached securely to the circuit breaker enclosure and are large enough to be readily seen. The tag or marker should clearly identify the circuit or machine receiving power through the circuit breaker.

  47. On Thursday, January 24, 2002, a 43 year old general inside laborer was fatally injured while performing electrical work on the 12,470 volt underground power center located on the 001-0 section. During retreat mining a length of high voltage cable was removed. Problems were encountered with re-energizing the power at the substation on the surface after the cable was re-stocked in the section power center. report The certified electrician came outside to check on the problem. When power was restored to the section it was discovered that the phasing was wrong. Power was removed from the section to correct the phasing. The victim was working on the leads inside the power center when the 001-0 section power was again re-energized from the surface, resulting in a fatal electrical accident.

  48. 104(a) Citation No. 7293099 was issued March 6, 2002, for a violation of 30 Code of Federal Regulations (CFR) 75.800: The high-voltage circuit entering the underground area of this coal mine did not have an effective device to provide protection against under-voltage, grounded phase, short circuit or overcurrent as tested on January 25, 2002.

  49. 104(d)(1) Order No. 7293100 was issued March 6, 2002, for a violation of 30 CFR 75.705-1(b): The high-voltage circuit supplying 12,470 VAC, three phase power to the underground areas of the mine was not determined to be properly deenergized by a qualified person before electrical work was performed on it.The evening shift foreman and electrician was the only qualified person at the mine on January 24, 2002. He deenergized the underground high-voltage visual disconnect but did not ensure that each ungrounded conductor of the high-voltage circuit upon which work was to be done was properly connected to the system-grounding medium.

  50. 104(d)(1) Order No. 7323521 was issued March 6, 2002, for a violation of 30 CFR 75.511: The visual disconnecting device at the surface substation for the underground high-voltage circuit at this mine was not locked out or suitably tagged by the person performing electrical work on this circuit on January 24, 2002. A general inside laborer performed electrical work on the underground high-voltage circuit without locking out or tagging the disconnecting device. The disconnecting device at the surface is the only means to disconnect the circuit. Also, electrical work was performed on a high-voltage distribution circuit by a non-qualified person not under the direct supervision of a qualified person at this mine. This resulted in fatal injuries to the general inside laborer. The evening shift foreman and electrician was the only qualified electrician at the mine. He was on the surface during this procedure and was aware that the inside laborer was performing electrical work. The inside laborer has not been a qualified electrician since January 01, 1983