Alpha Technologies UPE-6L - Manual (Page 15)

1. Pre-Installation
15 031-178-C0-001 Rev. A
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 Alpha 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 Electric Code (NEC) as well as local codes to ensure the breaker
will open, preventing unwanted current flow from posing a hazard to service personnel.
The second part of the safety ground arrangement is the ground path between the Alpha
enclosure and a second ground rod located at least 6 feet away from the driven ground rod at
the power pole. The second ground rod and enclosure are connected via an AWG #6 solid
copper wire buried at a depth of 8-12 inches. The wire is connected to the cabinet by means of
a ground lug on the back of the cabinet (for pole-mounted enclosures), or to a ground lug inside
the cabinet (for ground-mounted enclosures), and connected to the ground rod by means of a
listed grounding clamp suitable for direct burial, or exothermic weld. Normally it is specified that
the impedance of this ground can be no greater than 25 ohms at 60 Hertz. If, however, dual
ground rods are installed approximately eight feet apart, it is not necessary to measure the
impedance of the ground rods to meet the maximum 25 ohms specification—it is assumed that
the impedance specification is met.
Signal Ground
For proper operation, the Service Power Inserter must be securely grounded to the enclosure
chassis. This is of particular importance in systems utilizing an external status monitoring
transponder. The transponder chassis is grounded via a separate ground wire to the SPI case.
For systems utilizing an embedded transponder, the ground connection is made either through a
separate chassis ground block, or by means of the internal mounting hardware which then
grounds the transponder through the XM Series 2 Power Supply.
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 traveling through wires of varying impedance, can
produce high voltages which 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.
Low impedance grounding is not only critical for the proper operation of the cable system, but
also is mandatory for personnel safety.
1.4 Enclosure Grounding