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Electrical Inspection Procedures Handbook MSHA HANDBOOK SERIES U.S. Department of Labor Mine Safety and Health Administration Mine Safety and Health Enforcement December 2020 Handbook Number: PH20-V-5 Electrical Inspection Procedures Handbook PREFACE This handbook sets forth procedures for MSHA personnel to follow when conducting investigations and inspections of mines and facilities. Volume I provides guidance for electrical specialist, while Volume II provides guidance to MSHA general inspectors who encounter mine electrical systems and electric-powered equipment during the course of their inspections. Previously issued instructions for this same subject material are superseded by this handbook. Compliance related instructions that are contained in the MSHA Program Policy Manual remain in effect. Not all procedures and requirements are applicable for all mine types. Any deviation from the procedures outlined in this handbook should be based on the inspector’s professional judgement and discussion with the inspector’s supervisor, and consider conditions, practices, and circumstances specific to the mine. Table of Contents VOLUME I .................................................................................................................................................................. 1 CHAPTER 1 - INTRODUCTION ....................................................................................................................... 1-1 A. INSPECTION SCHEDULES .............................................................................................................................. 1-1 B. EQUIPMENT AND SUPPLIES .......................................................................................................................... 1-3 C. REFERENCES .................................................................................................................................................. 1-4 D. ELEMENTS OF ELECTRICAL INSPECTIONS .................................................................................................... 1-4 CHAPTER 2 - GROUNDING .............................................................................................................................. 2-1 A. GENERAL ...................................................................................................................................................... 2-1 B. APPROVED GROUNDING METHODS ............................................................................................................ 2-1 C. RESISTANCE GROUNDED SYSTEMS ............................................................................................................... 2-2 D. GROUNDED PHASE PROTECTION IN RESISTANCE GROUNDED SYSTEMS .................................................... 2-7 E. GROUND CHECK MONITOR TEST PROCEDURES .......................................................................................... 2-7 F. LIGHTNING ARRESTER GROUND FIELDS ................................................................................................... 2-10 G. SILICON DIODE GROUNDING TEST PROCEDURES...................................................................................... 2-11 H. METAL BATTERY CONNECTOR HOUSINGS ................................................................................................ 2-12 I. TESTING OF GROUNDING SYSTEMS IN METAL AND NONMETAL MINES .................................................. 2-13 CHAPTER 3 - CABLE INSULATION, PROTECTION, AND SPLICING .................................................. 3-1 A. GENERAL ...................................................................................................................................................... 3-1 B. OUTER JACKET OR INSULATION DAMAGE IN CABLES ................................................................................. 3-1 C. TRAILING CABLES ......................................................................................................................................... 3-2 D. CONTINUITY OF SHIELDING IN CABLE SPLICES ........................................................................................... 3-4 CHAPTER 4 – OVERCURRENT PROTECTION ............................................................................................ 4-1 A. GENERAL ...................................................................................................................................................... 4-1 B. CABLE AND CONDUCTOR AMPACITY .......................................................................................................... 4-1 C. CONDUCTOR AMPACITY FOR MOTOR CIRCUITS ......................................................................................... 4-2 D. GENERAL OVERCURRENT PROTECTION FOR ELECTRIC EQUIPMENT AND CIRCUITS ................................. 4-4 E. OVERLOAD AND SHORT CIRCUIT PROTECTION FOR MOTOR CIRCUITS ...................................................... 4-5 F. SHORT CIRCUIT PROTECTION FOR TRAILING CABLES ................................................................................. 4-8 G. EXAMPLES OF NONCOMPLIANCE ................................................................................................................. 4-8 CHAPTER 5 – HIGH VOLTAGE CIRCUIT BREAKERS AND SUBSTATIONS ..................................... 5-1 A. SAFETY PRECAUTIONS FOR HIGH VOLTAGE TESTING ................................................................................. 5-1 B. PROTECTION OF HIGH VOLTAGE CIRCUITS ................................................................................................. 5-5 C. UNDERVOLTAGE PROTECTION ..................................................................................................................... 5-5 D. GROUNDED-PHASE PROTECTION ................................................................................................................ 5-5 E. CURRENT TRANSFORMERS AND RELAY BURDEN ........................................................................................ 5-8 F. HOW TO CALCULATE SHORT CIRCUIT PROTECTION................................................................................... 5-9 G. HOW TO CALCULATE OVERCURRENT PROTECTION ................................................................................... 5-9 H. TESTING METHODS ..................................................................................................................................... 5-17 I. SURFACE TRANSFORMER STATION GUIDELINES ....................................................................................... 5-18 CHAPTER 6 - PERMISSIBILITY ........................................................................................................................ 6-1 A. INSPECTION PROCEDURES ............................................................................................................................ 6-1 B. FIELD MODIFICATION PROCEDURES ............................................................................................................ 6-4 Table of Contents C. FIELD MODIFICATION REPORTS ................................................................................................................... 6-5 D. DISTRICT FIELD CHANGES............................................................................................................................ 6-5 CHAPTER 7 – GENERAL ..................................................................................................................................... 7-1 A. GUIDELINES FOR USING THE NATIONAL ELECTRICAL CODE ..................................................................... 7-1 B. GUIDELINES FOR DETERMINING PORTABLE, MOBILE, AND STATIONARY ELECTRIC EQUIPMENT LOCATED ON THE SURFACE .................................................................................................................................................. 7-2 C. GUIDELINES FOR PERMITTING NON-EXPLOSION-PROOF AIR HEATING UNITS IN HAZARDOUS LOCATIONS ON THE SURFACE .................................................................................................................................................. 7-2 D. ELECTRICAL SWITCH EVALUATION CRITERIA ............................................................................................. 7-3 E. LIGHTNING ARRESTERS ................................................................................................................................ 7-4 F. INTERMACHINE ARCING TEST PROCEDURES ............................................................................................... 7-5 G. EVALUATING ELECTRIC EQUIPMENT MAINTENANCE PROGRAMS FOR COAL MINES ............................... 7-7 H. ADDITIONAL PROCEDURES WHEN USING A SAFETY CIRCUIT TESTER ........................................................ 7-7 I. ELECTROMAGNETIC INTERFERENCE ............................................................................................................ 7-8 J. LONGWALL ELECTRICAL INSPECTIONS ....................................................................................................... 7-8 VOLUME II ............................................................................................................................................................ II-1 CHAPTER 1 - INTRODUCTION ...................................................................................................................... II-1 CHAPTER 2 - GROUNDING ............................................................................................................................. II-1 CHAPTER 3 - CABLE INSULATION,
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