The excess space inside electrical supply stations (substations) is often considered for storage of construction materials.
The National Electrical Safety Code® (NESC®) in Rule 110B2 prohibits storage inside an electrical supply station even when stored well away from the energized conductors and equipment. The only exception is the storage of minor parts essential to the maintenance of the installed equipment, i.e., fuses, switch handles. The rule does not prohibit the expansion or maintenance within the supply station. Construction materials associated with the expansion/maintenance may be stored within the supply station during the construction period provided qualified personnel do the work and all clearance requirements are met while work is being performed. Qualified personnel are people with adequate knowledge of the installation, construction and operation of apparatus and the associated hazards. The intent of Rule 110 is to keep unqualified people out of supply stations. You may recall from my November/December 1997 IAEI article, “A Substation is Not Just a Fence,” a supply station can be a very hazardous place to unqualified personnel because the NESC® electrical clearance requirements inside the supply station are considerably less than that required for areas accessible to the general public.
Storage inside a supply station invites unqualified personnel into the supply station. The stores or delivery personnel delivering material to the supply station may not be qualified to enter and unload materials in a supply station. The construction personnel who enter the supply station to pick up the materials may not be qualified to enter and load materials in a supply station. Storage of materials attracts would-be thieves into the supply station.
When space permits, an interior fence or other barrier can be installed to partition off the storage area from the electric supply equipment space. The interior fence or barrier must meet the requirements of Rule 110A (height, signage and safety clearance zone) and grounded in accordance with Rule 92E. Entrances to the storage area should be located so that personnel dealing with the storage do not have to pass through the supply equipment space. If a chain link fence is used around the storage area in lieu of a solid barrier, I recommend suitable visual barrier webbing be laced into the fence fabric to limit the attraction to would-be thieves.
If you have general questions about the NESC, please call me at 302-454-4910 or e-mail me atdave.young@conectiv.com.
National Electrical Safety Code and NESC are registered trademarks of the Institute of Electrical and Electronics Engineers.