Alpha Technologies LPE Enclosure - Manual (Page 8)

8 031-302-B0-001 Rev A
Grounding Connection Notes
In order to provide a ready, reliable source of backup power, it is necessary to connect the power supply to an
effective grounding and Earthing system that not only provides for the safety of the service personnel responsible
for its operation and maintenance, but also facilitates the proper operation and protection of the equipment within
the network. Such a grounding system provides protection with respect to operator safety, system communication,
and equipment protection.
Safety Ground
The safety ground is a two-part system, comprised of the utility service and the Alpha system.
1. First, utility service;
As a minimum requirement for the protection of Alpha equipment, the local utility service must provide a low-
impedance path for fault current return to earth. This must meet or exceed the requirements of the US National
Electrical Code. The connection between the Alpha Power Supply and the utility must also meet or exceed the
requirements of the US National Electrical Code.
2. Second, the Alpha grounding system;
The Alpha grounding system consists of a low-impedance connection between the enclosure and an Earth Ground
(located at least 6' away from the Utility Earth connection).
This impedance between the enclosure and Earth must be 25 Ohms or less at 60 Hertz.
Local soil conditions will determine the complexity of the grounding system required to meet the 25 Ohm
(maximum) resistance specified above.
For example, a single 8' ground rod may be sufficient to meet the requirement. In some cases, a more elaborate
system may be required such as multiple ground rods connected by a #6AWG solid copper cable buried 8-12"
below the surface. Where this is not possible, contact a local grounding system expert for alternate methods that
will meet the 25 Ohm (maximum) specification.
Strike (Lightning) Ground
Lightning strikes, grid switching, or other aberrations on the power line and/or communications cables have the
potential to cause high-energy transients which can damage the powering or communications systems. Without
a low-impedance path to the ground, the current, when traveling through wires of varying impedance, produce
damaging high voltage. The most viable method available to protect the system from damage is to divert these
unwanted high-energy transients along a low-impedance path to ground. A low-impedance path to ground
prevents these currents from reaching high voltage levels and posing a threat to equipment. The single-point
grounding system provides a low-impedance path to ground, and the key to its success is the proper bonding of the
grounding rods, so the components of the grounding system appear as a single point of uniform impedance. Alpha
recommends the use of a surge arresting device electrically bonded to the Alpha Ground System.
All ground rod connections must be made by means of a listed grounding clamp suitable for direct burial or
exothermically welded.
NOTE:
Low-impedance grounding is mandatory for personnel safety and critical for the proper
operation of the cable system.
WARNING!