High voltage grounding

Source excerpt

# Occupational Safety and Health Administration (cont.) ## III. Protecting Workers From Hazardous Differences in Electrical Potential (cont.) - grounded at a remote location can experience hazardous potential differences if the cable becomes energized or if a fault occurs on a different, but nearby, energized cable. The fault current causes potential gradients in the earth, and a potential difference will exist between the earth where the worker is standing and the earth where the cable is grounded. Consequently, to create an equipotential zone for the worker, the employer must provide a means of connecting the deenergized cable to ground at the worksite by having the worker stand on a conductive mat bonded to the deenergized cable. If the cable is cut, the employer must install a bond across the opening in the cable or install one bond on each side of the opening to ensure that the separate cable ends are at the same potential. The employer must protect the worker from any hazardous differences in potential any time there is no bond between the mat and the cable (for example, before the worker installs the bonds). 3. Other safety-related considerations. To ensure that the grounding system is safe and effective, the employer should also consider the following factors: [5] i. Maintenance of grounding equipment. It is essential that the employer properly maintain grounding equipment. Corrosion in the connections between grounding cables and clamps and on the clamp surface can increase the resistance of the cable, thereby increasing potential differences. In addition, the surface to which a clamp attaches, such as a conductor or tower member, must be clean and free of corrosion and oxidation to ensure a low-resistance connection. Cables must be free of damage that could reduce their current-carrying capacity so that they can carry the full fault current without failure. Each clamp must have a tight connection to the cable to ensure a low resistance and to ensure th…

Source excerpt

# Electrical Power Generation, Transmission, and Distribution (cont.) ## [redacted phone] Testing and test facilities (cont.) RR Electrical Power Generation, Transmission, and Distribution Division 2 AO 2-2017 Oregon Administrative Rules Oregon Occupational Safety and Health Division (a)The employer must provide safeguarding within test areas to control access to test equipment or to apparatus under test that could become energized as part of the testing by either direct or inductive coupling and to prevent accidental employee contact with energized parts. (b) The employer must guard permanent test areas with walls, fences, or other barriers designed to keep employees out of the test areas. (c) In field testing, or at a temporary test site not guarded by permanent fences and gates, the employer must ensure the use of one of the following means to prevent employees without authorization from entering: (A) Distinctively colored safety tape supported approximately waist high with safety signs attached to it, (B) A barrier or barricade that limits access to the test area to a degree equivalent, physically and visually, to the barricade specified in paragraph (3)(c)(A) of this rule, or (C) One or more test observers stationed so that they can monitor the entire area. (d) The employer must ensure the removal of the safeguards required by paragraph (3)(c) of this rule when employees no longer need the protection afforded by the safeguards. (4) Grounding practices. (a) The employer must establish and implement safe grounding practices for the test facility. (A) The employer must maintain at ground potential all conductive parts accessible to the test operator while the equipment is operating at high voltage. (B) Wherever ungrounded terminals of test equipment or apparatus under test may be present, they must be treated as energized until tests demonstrate that they are deenergized. (b) The employer must ensure either that visible grounds a…

Source excerpt

# 1926.1406 ASSEMBLY/DISASSEMBLY-EMPLOYER PROCEDURES -GENERAL REQUIREMENTS (cont.) ## 1926.1408(g) Training. (cont.) - 1926.1408(g)(1)(i)(A) Information regarding the danger of electrocution from the operator simultaneously touching the equipment and the ground. - 1926.1408(g)(1)(i)(B) The importance to the operator's safety of remaining inside the cab except where there is an imminent danger of fire, explosion, or other emergency that necessitates leaving the cab. - 1926.1408(g)(1)(i)(C) The safest means of evacuating from equipment that may be energized. - 1926.1408(g)(1)(i)(D) The danger of the potentially energized zone around the equipment (step potential). - 1926.1408(g)(1)(i)(E) The need for crew in the area to avoid approaching or touching the equipment and the load. - 1926.1408(g)(1)(i)(F) Safe clearance distance from power lines. - 1926.1408(g)(1)(ii) Power lines are presumed to be energized unless the utility owner/operator confirms that the power line has been and continues to be deenergized and visibly grounded at the worksite. - 1926.1408(g)(1)(iii) Power lines are presumed to be uninsulated unless the utility owner/operator or a registered engineer who is a qualified person with respect to electrical power transmission and distribution confirms that a line is insulated. .1408(g)(1)(iv) The limitations of an insulating link/device, proximity alarm, and range control (and similar) device, if used. - 6.1408(g)(1)(v) The procedures to be followed to properly ground equipment and the limitations of grounding. - 1926.1408(g)(2) Employees working as dedicated spotters must be trained to enable them to effectively perform their task, including training on the applicable requirements of this section. - 1926.1408(g)(3) Training under this section must be administered in accordance with 1926.1430(g). 1926.1408(h) Devices originally designed by the manufacturer for use as: A safety device (see 1926.1415), operational aid, or a means to prevent powe…

Source excerpt

# 1926.962 GROUNDING FOR THE PROTECTION OF EMPLOYEES (cont.) 1926.962(g) Additional precautions. The employer shall ensure that, when an employee performs work on a cable at a location remote from the cable terminal, the cable is not grounded at the cable terminal if there is a possibility of hazardous transfer of potential should a fault occur. 1926.962(h) Removal of grounds for test. The employer may permit employees to remove grounds temporarily during tests. During the test procedure, the employer shall ensure that each employee uses insulating equipment, shall isolate each employee from any hazards involved, and shall implement any additional measures necessary to protect each exposed employee in case the previously grounded lines and equipment become energized. FR [redacted postal code]-[redacted postal code], July 10, 2014] ## 1926.963 TESTING AND TEST FACILITIES 1926.963(a) Application. This section provides for safe work practices for high-voltage and high-power testing performed in laboratories, shops, and substations, and in the field and on electric transmission and distribution lines and equipment. It applies only to testing involving interim measurements using high voltage, high power, or combinations of high voltage and high power, and not to testing involving continuous measurements as in routine metering, relaying, and normal line work. Note to paragraph (a): OSHA considers routine inspection and maintenance measurements made by qualified employees to be routine line work not included in the scope of this section, provided that the hazards related to the use of intrinsic high voltage or high-power sources require only the normal precautions associated with routine work specified in the other paragraphs of this subpart. Two typical examples of such excluded test work procedures are "phasing-out" testing and testing for a "no-voltage" condition. - 1926.963(b) General requirements. - 1926.963(b)(1) Safe work practices. The employer shall establi…

Source excerpt

# 1926.962 GROUNDING FOR THE PROTECTION OF EMPLOYEES 1926.962(a) Application. This section applies to grounding of transmission and distribution lines and equipment for the purpose of protecting employees. Paragraph (d) of this section also applies to protective grounding of other equipment as required elsewhere in this Subpart. Note to paragraph (a): This section covers grounding of transmission and distribution lines and equipment when this subpart requires protective grounding and whenever the employer chooses to ground such lines and equipment for the protection of employees. 1926.962(b) General. For any employee to work transmission and distribution lines or equipment as deenergized, the employer shall ensure that the lines or equipment are deenergized under the provisions of $1926.961 and shall ensure proper grounding of the lines or equipment as specified in paragraphs (c) through (h) of this section. However, if the employer can demonstrate that installation of a ground is impracticable or that the conditions resulting from the installation of a ground would present greater hazards to employees than working without grounds, the lines and equipment may be treated as deenergized provided that the employer establishes that all of the following conditions apply: - 1926.962(b)(1) Deenergized. The employer ensures that the lines and equipment are deenergized under the provisions of $1926.961. 1926.962(b)(2) No possibility of contact. There is no possibility of contact with another energized source. 1926.962(b)(3) No induced voltage. The hazard of induced voltage is not present. 1926.962(c) Equipotential zone. Temporary protective grounds shall be placed at such locations and arranged in such a manner that the employer can demonstrate will prevent each employee from being exposed to hazardous differences in electric potential. Note to paragraph (c): Appendix C to this subpart contains guidelines for establishing the equipotential zone required by this paragra…

Source excerpt

# 1926.962 GROUNDING FOR THE PROTECTION OF EMPLOYEES (cont.) ## 1926.963 TESTING AND TEST FACILITIES (cont.) 1926.963(d)(2) Installation of grounds. The employer shall ensure either that visible grounds are applied automatically, or that employees using properly insulated tools manually apply visible grounds, to the high-voltage circuits after they are deenergized and before any employee performs work on the circuit or on the item or apparatus under test. Common ground connections shall be solidly connected to the test equipment and the apparatus under test. 1926.963(d)(3) Isolated ground return. In high-power testing, the employer shall provide an isolated ground-return conductor system designed to prevent the intentional passage of current, with its attendant voltage rise, from occurring in the ground grid or in the earth. However, the employer need not provide an isolated ground-return conductor if the employer can demonstrate that both of the following conditions exist: 1926.963(d)(3)(i) The employer cannot provide an isolated ground-return conductor due to the distance of the test site from the electric energy source, and - 1926.963(d)(3)(ii) The employer protects employees from any hazardous step and touch potentials that may develop during the test. Note to paragraph (d)(3)(ii): See Appendix C to this subpart for information on measures that employers can take to protect employees from hazardous step and touch potentials. - 1926.963(d)(4) Equipment grounding conductors. For tests in which using the equipment grounding conductor in the equipment power cord to ground the test equipment would result in greater hazards to test personnel or prevent the taking of satisfactory measurements, the employer may use a ground clearly indicated in the test set-up if the employer can demonstrate that this ground affords protection for employees equivalent to the protection afforded by an equipment grounding conductor in the power supply cord. - 1926.963(d)(5) Ground…

Source excerpt

# Occupational Safety and Health Administration (cont.) ## III. Protecting Workers From Hazardous Differences in Electrical Potential (cont.) 2. Insulating equipment, such as rubber gloves, can protect employees handling grounded equipment and conductors from hazardous touch potentials. The insulating equipment must be rated for the highest voltage that can be impressed on the grounded objects under fault conditions (rather than for the full system voltage). 3. Restricting employees from areas where hazardous step or touch potentials could arise can protect employees not directly involved in performing the operation. The employer must ensure that employees on the ground in the vicinity of transmission structures are at a distance where step voltages would be insufficient to cause injury. Employees must not handle grounded conductors or equipment likely to become energized to hazardous voltages unless the employees are within an equipotential zone or protected by insulating equipment. Submit Feedback