Electrical Hazards

21 Ways to Verify Safety of Electrical Equipment Over 600 Volts

Date First Published on SafetySmart Compliance: April 23rd, 2013
Topics: Electricity |

Electrical equipment over 600 voltsThe OSHA Electrical Standard 1910.303(b) requires you to keep electric equipment “free from recognized hazards likely to cause death or serious physical harm” to workers. To comply, you must evaluate not just the actual equipment but how it’s installed and used. Here are the 21 things to check for equipment over 600 volts. (Click here for requirements for equipment under 600 volts.)

MAKE SURE:

1. A wall, screen or fence is used to enclose outdoor electrical installations and deter access by persons who aren’t qualified.

2. Fences are at least 2.13 m (7.0 ft) high or a combination of 1.80 m (6.0 ft) high or more of fence fabric and a 305-mm (1-ft) or more extension utilizing 3 or more strands of barbed wire or equivalent.

3. Indoor installations accessible to those who aren’t qualified persons meet the following requirements:

  • The installations are made with metal-enclosed equipment or enclosed in a vault or in an area to which access is controlled by a lock;
  • Metal-enclosed switchgear, unit substations, transformers, pull boxes, connection boxes and other similar equipment is marked with appropriate caution signs; and
  • Openings in ventilated dry-type transformers and similar openings in other equipment are designed so that foreign objects inserted through these openings are deflected from energized parts.

4. Outdoor electrical installations with exposed live parts are accessible only to qualified persons.

5. Outdoor enclosed equipment accessible to unqualified employees meet all of the following requirements:

  • Ventilating or similar openings in equipment are designed so that foreign objects inserted through the openings are deflected from energized parts;
  • Where necessary, suitable guards are in place to prevent physical damage from vehicular traffic;
  • Nonmetallic or metal-enclosed equipment located outdoors and accessible to the general public are designed so that exposed nuts or bolts can’t be readily removed, permitting access to live parts;
  • Where nonmetallic or metal-enclosed equipment is accessible to the general public and the bottom of the enclosure is less than 2.44 m (8.0 ft) above the floor or grade level, the enclosure door or hinged cover is kept locked; and
  • Doors and covers of enclosures used solely as pull boxes, splice boxes or junction boxes are locked, bolted, or screwed on, except for underground box covers that weigh over 45.4 kg (100 lb).

6. There’s enough space around electric equipment to permit ready and safe operation and maintenance.

7. Where energized parts are exposed, the minimum clear work space is:

  • At least1.98 m (6.5 ft) high (measured vertically from the floor or platform);
  • At least 914 mm (3.0 ft) wide (measured parallel to the equipment);
  • Of a depth that meets the requirements set out in Table S-2 below; and
  • Adequate to permit at least a 90-degree opening of doors or hinged panels.

8. There’s at least one entrance that’s at least 610 mm (24 in.) wide and 1.98 m (6.5 ft) high to give access to the working space about electric equipment.

9. There’s one entrance at each end of switchboard and control panels over 1.83 m (6.0 ft) in width, unless the location of such panels permits a continuous and unobstructed way of exit travel, or the required work space is doubled.

10. Where one entrance to the working space is permitted, the entrance is located so that the edge of the entrance nearest the switchboards and control panels is at least the minimum clear distance listed in Table S-2 below away from such equipment.

11. Any bare energized parts at any voltage or insulated energized parts above 600 volts, nominal, to ground located adjacent to such entrance, are suitably guarded.

12. There are permanent ladders or stairways providing safe access to the working space around electric equipment installed on platforms, balconies, mezzanine floors or in attic or roof rooms or spaces.

13. The minimum clear working space in the direction of access to live parts of electric equipment is no less than listed in Table S-2 below, with distances measured from the live parts, if they’re exposed, or from the enclosure front or opening, if they’re enclosed.

14. The high-voltage equipment is effectively separated from the space occupied by the low-voltage equipment by a suitable partition, fence or screen where there are any switches, cutouts or other equipment operating at 600 volts, nominal, or less, installed in a room or enclosure where there are exposed live parts or exposed wiring operating at over 600 volts, nominal.

15. Entrances to buildings, rooms or enclosures containing exposed live parts or exposed conductors operating at over 600 volts, nominal:

  • [  ] Are kept locked or under the observation of a qualified person at all times; and
  • [  ] Are marked by permanent and conspicuous warning signs shall be provided, reading substantially as follows: “DANGER — HIGH VOLTAGE — KEEP OUT.”

16. All working spaces about electric equipment are adequately illuminated.

17. The lighting outlets are arranged so as not to endanger persons changing lamps or making repairs on the lighting system by live parts or other equipment.

18. The points of control are located so as to prevent contact with any live part or moving part of the equipment while turning on the lights.

19. Unguarded live parts above working space are kept at elevations no less than specified in Table S-3 below.

20. There are no pipes or ducts foreign to the electrical installation that require periodic maintenance or whose malfunction would endanger the operation of the electrical system in the vicinity of service equipment, metal-enclosed power switchgear or industrial control assemblies.

21. Protection is provided where necessary to avoid damage from condensation leaks and breaks in such foreign systems.

  • Note: Piping and other facilities aren’t considered foreign if provided for fire protection of the electrical installation.

Table S-2. Minimum Depth of Clear Working Space at Electric Equipment, Over 600 V

Nominal voltage to ground

Minimum clear distance for condition2 3

Condition A

Condition B

Condition C

m

ft

M

ft

m

ft

601-2500 V

2501-9000 V

9001 V-25 kV

Over 25-75 kV1

Above 75 kV1

0.9

1.2

1.5

1.8

2.5

3.0

4.0

5.0

6.0

8.0

1.2

1.5

1.8

2.5

3.0

4.0

5.0

6.0

8.0

10.0

1.5

1.8

2.8

3.0

3.7

5.0

6.0

9.0

10.0

12.0

Notes to Table S-2:

1 Minimum depth of clear working space in front of electric equipment with a nominal voltage to ground above 25,000 volts may be the same as that for 25,000 volts under Conditions A, B and C for installations built before April 16, 1981.

2 Conditions A, B, and C are as follows:

Condition A — Exposed live parts on one side and no live or grounded parts on the other side of the working space, or exposed live parts on both sides effectively guarded by suitable wood or other insulating material. Insulated wire or insulated busbars operating at not over 300 volts are not considered live parts.

Condition B — Exposed live parts on one side and grounded parts on the other side. Concrete, brick, and tile walls are considered as grounded surfaces.

Condition C — Exposed live parts on both sides of the work space (not guarded as provided in Condition A) with the operator between.

3 Working space is not required in back of equipment such as dead-front switchboards or control assemblies that has no renewable or adjustable parts (such as fuses or switches) on the back and where all connections are accessible from locations other than the back. Where rear access is required to work on the deenergized parts on the back of enclosed equipment, a minimum working space 762 mm (30 in.) horizontally shall be provided.

Table S-3. Elevation of Unguarded Live Parts Above Working Space

Nominal voltage between phases

Elevation

m

ft

601-7500 V

7501 V-35 kV

Over 35 kV

12.8

2.8

2.8 + 9.5 mm/kV over 35 kV

19.0

9.0

9.0 + 0.37 in./kV over 35 kV

Note to Table S-3

1The minimum elevation may be 2.6 m (8.5 ft) for installations built before August 13, 2007. The minimum elevation may be 2.4 m (8.0 ft) for installations built before April 16, 1981, if the nominal voltage between phases is in the range of 601-6600 volts.

Ensure Compliance with Electrical Equipment Rules

Go to the SafetySmart Compliance Electricity Compliance Center to get more help complying with OSHA electrical safety requirements: