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Grounding and the Use of the Signal Reference Grid in Data Centers

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The signal reference grid (SRG) is a network of copper wires typically installed below a raised floor in a data center as shown in Figure 1. An SRG can also be constructed of flat copper straps, aluminum wires, raised flooring substructure, or in extreme cases, a solid covering of sheet metal. The installation of signal reference grids has been common practice for over 30 years. Most data center designs call out for SRGs and their use and expense are not questioned.

Recently, more and more data centers are being constructed on existing hard-floor environments where SRGs cannot be installed under the floor. The evidence suggests that the lack of SRGs in such installations has given rise to no adverse effects on the operation of the IT equipment. Naturally this leads to the question of why systems can work reliably without an SRG and whether the SRG is ever a necessary or logical...

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Panduit StructuredGround™ Grounding System for Data Center Grounding

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The Purpose of Grounding

The grounding system is not just an insurance policy against a lightning strike. It is an active, functioning system that provides protection for personnel and equipment. Proper grounding is essential for efficient network performance. The purpose of the grounding system is to create a low impedance path to earth ground for electrical surges and transient voltages. Lightning, fault currents, circuit switching (motors turning on and off), and electrostatic discharge are the common causes of these surges and transient voltages. An effective grounding system minimizes the detrimental effects of these electrical surges. A properly designed grounding system is one that is intentional, visually verifiable, adequately sized to handle expected currents safely, and one that directs these potentially damaging currents away from sensitive communication equipment. Any metallic component that is part of the data center infrastructure (such as equipment, racks, ladder racks, enclosures, cable trays, etc.) must be bonded to the grounding system....

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Arc Flash Analysis: IEEE Method versus the NFPA 70E Tables

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1.0 Abstract

Recent changes in workplace safety regulations have heightened the awareness of hazards associated with electrical arcs. The hazard level must be quantified and workers properly protected before entering proximity of exposed energized conductors. National Fire Protection Association’s (NFPA) standard 70E provides the guidelines for work involving electrical hazards and the selection of arc flash protective equipment. In order to properly select the protective gear one must have knowledge of the potential thermal energy of the electric arc. Institute of Electrical and Electronics Engineers (IEEE) standard 1584 has been the de facto standard for calculating the arc energy levels at different points in the electrical power system.

However, NFPA 70E also provides the option of using the Hazard/Risk Category (HRC) task tables for personal protective equipment (PPE) selection. These tables provide pre-defined levels of PPE, which are based on the available short circuit current and the speed of the overcurrent protective device...

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