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 LANTNAVFACENGCOM A&E GUIDE
3/93
CABLE SHIELDS
A.3.1.3
Use tape shielded cables and ensure minimum cable bending radii of 12 times
the overall cable diameter; use wire shielded cables (see NEMA WC 8,
"Ethylene-Propylene-Rubber-Insulated Wire and Cable for the Transmission
and Distribution of Electrical Energy," for minimum cable bending radii) only
where existing manholes are utilized and the minimum cable bending radii of
tape shielded cables cannot be realized. Please note that the minimum cable
bending radii refers to the inner surface of the cable and not to the axis of
the cable.
A.3.1.4
NUMBER OF CONDUCTORS
Use l/c cables when solid dielectric cables are specified; 3/c cable may be
used when special conditions justify its use.
A.3.1.5
EXISTING CONDITIONS
Ensure that new cables and specified splicing methods are compatible with
existing cables. Provide the same information (e.g., insulation type, insulation
rating, conductor type, and number of conductors) for existing cables as
required for new cables. Caution: Existing cable may be fireproofed with
asbestos in manholes. Refer to paragraph A.1.10.
A.3.2
TRANSFORMERS
A.3.2.1
PAD-MOUNTED TRANSFORMER VERSUS SECONDARY UNIT
SUBSTATION
Pad-mounted transformers are normally used for 750 kVA and below on
15 kV systems and for 500 kVA and below on 5 kV systems. For voltages
above 15 kV and for kVA ratings above those previously indicated, it is
preferable to use secondary unit substations. When using a pad-mounted
transformer, select the applicable pad-mounted transformer detail from
Figures 3 through 8, supply the missing data. and incorporate that detail onto
the contract drawings. Do not use these details to depict secondary unit
substations.
A.3.2.2
LOCATION
Transformer location with respect to buildings shall meet requirements of
MIL-HDBK-1008, "Fire Protection for Facilities Engineering Design and
Construction" and NFPA 70.
Attachment A-18
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