Alpha Technologies FlexNet FMPS - Manual (Page 11)

v
Grounding Connection Notes
In order to provide a ready, reliable source of backup power it is necessary to establish a grounding 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 will
provide protection with respect to operator safety, system communication, and equipment protection.
Safety Ground
The safety ground is a two-part system. The first part is a return path for stray current back to the input breaker,
and the second is a return path from the enclosure to a second ground rod.
Typically, the safety, or utility ground, provides a return path to the input breaker or fuse panel by means of a
connection to an appropriate driven ground rod at the base of the power pole. This path must meet National
Electrical Code (NEC) as well as local codes to ensure the breaker will open, preventing unwanted current flow
from posing a hazard to service personnel.
Strike (Lightning) Ground
Lightning strikes, grid switching, or other aberrations on the power line all have the potential to cause “fast rise-
time currents” which can cause damage to the powering system. Without a low-impedance path to ground, the
current, while travelling through wires of varying impedance, can produce high voltages that will damage the
powering equipment. The most viable method available to protect the system from damage is to divert these
unwanted “fast rise-time currents” along a low-impedance path to ground. A low-impedance path to ground will
prevent 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 ground rods, so the components of the grounding system appear as a single point of uniform impedance.