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 4.4.4
Marshalling Yards (Truck and Railroad). Provide a primary
protection system consisting of overhead conductors spanned between structural
supports and connected to a primary ground counterpoise. Ground all metal
parts and reinforcing steel of above grade structures to the ground
counterpoise. The reinforcing steel of precast concrete slabs should be
grounded, but where inaccessible within the slabs, it is permissible to omit
such grounding. Ground railroad tracks 10 ft (3.05 m) or more outside of
barriers at entrances and exits to the yard and where they cross a
counterpoise (see Figure 1).
4.4.5
Railroad Sidings. Provide a primary protection system consisting of
overhead conductors spanned between structural supports and connected to
ground rods. Ground all metal parts and reinforcing steel of aboveground
structure to driven ground rods. Ground all railroad tracks to ground rods
located 10 ft (3.05 m) or more outside of the entrance to barrier.
4.4.6
Electric Service. Electric and communication services to explosives
operating buildings and magazines shall be run underground in metallic conduit
for the last 50 ft (15 m). Services to buildings not containing explosives
may be overhead. The line side of the main protective device shall be
provided with suitable surge arresters. Surge arresters shall be located at
the service transition to underground conduit outside the 50 ft (15 m) limit.
A separate ground shall be provided at the secondary electric service
entrance. This ground shall be bonded to the facility ground counterpoise.
The electric supply to an explosives area shall be arranged so that it can be
cut off by switching devices located at one or more control points outside of
and immediately adjacent to the explosives areas.
4.4.7
Exterior Overhead Pipelines. Bond overhead pipes which enter a
building, storage facility, or area to all metal objects that are within
sideflash clearance of the pipes where they are in a zone of lightning
protection. Pipe segments shall be electrically continuous.
4.4.8
Fences. Fences shall be grounded on each side of every gate, at
points 150 ft (45 m) on each side of high-tension line crossings, and at 150
ft (45 m) intervals along the fence where high-tension lines (as defined by
ANSI C2) are directly overhead and run parallel to the fence. Fences shall
be grounded every 1,000 ft to 1,500 ft (300 m to 450 m) of length when fences
are in isolated places and at lesser distances depending upon proximity of
fence to public roads, highways, and buildings. The ground shall be made with
a bolted connection at a fence post by the use of No. 2/0 AWG (67.4 mm)
copper cable. Where plastic coated fabric is used, the post shall be bolted,
and each strand of the fence shall be brazed to the metallic bare conductors.
The conductors shall then be grounded.
4.5
Generating Plants. Commercial type, metal-oxide, surge arresters
shall be provided on all overhead feeders adjacent to a plant as described in
paras. 4.5.1 and 4.5.2.
4.5.1
Surge Protection. Surge protection shall be provided between the
aerial surge arresters and generator or on a bus for several generators.
Where a generator is connected to an overhead line through a transformer,
provide a station type surge arrester on the high voltage side of the
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