Alpha Node Manuel d'installation télécharger pdf (Page 9)

031-295-B0-001 Rev.A

1.0 Introduction

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 speciﬁ ed above.

For example, a single 8’ ground rod may be sufﬁ cient 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) speciﬁ cation.

All ground rod connections must be made by means of a listed grounding clamp suitable for direct burial or

exothermically welded.

Signal Ground

For proper operation, the Service Power Inserter (SPI) must be securely grounded to the enclosure chassis. This is of

particular importance in systems using an external status monitoring transponder. The transponder chassis is grounded

via a separate ground wire to the SPI case. For systems using an embedded transponder, the ground connection is

made either through a separate chassis ground block, or by means of the internal mounting hardware which grounds

the transponder through the XM2/XM2HP power supply. Please refer to the appropriate Communications product

manual for installation procedures.

Strike (Lightning) Ground

Lightning strikes, grid switching, or other aberrations on the power line and/or communications cable have the

potential to cause high-energy transients which can damage the powering or communitations systems. Without a low-

impedance path to 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 ground 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.

Low impedance grounding is mandatory for personnel safety and critical for the proper

operation of the cable system .

WARNING!

NOTE:

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Alpha Node Manuel d'installation Page 9

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