standards and guidelines for communication sites - Radio And ...

STANDARDS AND GUIDELINES FOR COMMUNICATION SITES AC POWER SPD REQUIREMENTS
7.4.1.2 INSTALLATION WITH MAIN DISCONNECT AWAY FROM AREA
For installations where the main disconnecting means is located away from the shelter, room or
equipment area (Diagrams B through J; Figures 7-6 through 7-11 on pages 7-15 through 7-20,
respectively), a separately derived electrical system is an option within the shelter, room or equipment
area to establish the neutral-ground bond. Other means are described in “Location of Neutral-Ground
Bond” on page 6-4.
A separately derived electrical system can be achieved by installation of a step down or isolation
transformer, or by the installation of a suitable UPS that qualifies as a separately derived electrical
system. Similarly, when a power feed is provided to another building, shelter or equipment area
(Diagrams K through M; Figures 7-12 through 7-14 on pages 7-21 through 7-23, respectively), a
separately derived electrical system should be installed within that shelter, building or equipment area to
minimize potential damage resulting from power line anomalies generated by loads or lightning activity
within that shelter, building or equipment area.
7.4.1.3 INSTALLATION WITH EQUIPMENT INSTALLED IN POLE OR PAD MOUNTED CABINETS
For installations where the equipment is installed within pole or pad mounted cabinets (Diagrams N
through P; Figures 7-15 through 7-17 on pages 7-24 through 7-26), SPDs are required as specified in
Table 7-1. Where a pole or pad mounted cabinet is installed and the electrical feeder originates from
within another building or shelter (Diagram Q; Figure 7-18 on page 7-27), a Type 3 SPD is required to
be installed on all equipment within the cabinet. In installations of this type it may be desirable to install
additional SPDs at the branch circuit panelboard. Where the level of exposure is high a Type 1 SPD is
recommended. See Table 7-1 and footnotes for further information.
NOTE: Single conversion (forward transfer mode) UPS systems do not provide transient voltage surge
suppression. Double conversion (reverse transfer mode or rectifier-inverter) UPS systems offer surge
suppression to source induced transients. No surge suppression is afforded for load induced transients
on either type.
TABLE 7-1 REQUIRED TVSS PROTECTION FOR VARIOUS SERVICE TYPES
Service Type
Interconnect
Diagram
(Fig. No.)
Stand-alone Building/shelter without Generator
Main service disconnect and all
panelboards located within the
same shelter, room or equipment
area
Main service disconnect located
outside the equipment area
(greater than 3 m (10 ft.)):
• At fence or property line
utilizing a separately
derived system supplying
equipment area
A
(Figure 7-2)
B
(Figure 7-3)
Main
Disconnect
Main
Panelboard
or Feeder
Side of ATS
Utility
Panelboard
Utility
Panelboard
in Other
Bldg./Shelter
Equipment
(If > 3 m
(10 ft.) from
panelboard)
Type 1 Type 3 1
Type 1 Type 3 1
68P81089E50-B 9/1/05 7-7