Data Centers -NFPA 72 2022.pdf

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FIRE &LIFE SAFETY

WINTER EDITION

Contents

3 -Why is ground fault protection needed?18-STIValuedPartnerships19 -What to look for in NFPA 72-202231-Firestopping in Mass Timber Construction37-How smart buildings bat health concerns48-NECchangesenhanceresiliency62 - Designing an emergency power supply system

Why is ground fault protectionneeded?

Why is ground fault protection needed?

STI Valued PartnershipsWhattolookforinNFPA72-2022

Electricalsystemgroundfaultprotectionisvitaltoensurethesafetyofpersonnelandequipmentandtoreliablymaintainsystemsbasedontheloadstheyserve

Firestopping in Mass TimberConstruction

attention when discussing electrical system protectionground faults actuallypresent a far more mon and - in aggregate - potentially more dangerous occur-rence for personnel and equipment. Groundingbonding and ground fault protectionare vital to decrease shock hazards to personnel during a ground fault such as when acurrent-carrying conductor's insulation fails or inadvertently faults to ground.

How smart buildings bathealth concerns

NEC changes enhanceresiliency

Designing an emergencypower supply system

Ground fault protection allows an electrical system to be maintained in a reliable man-ner matching the needs/loads it serves and to isolate undesirable fault conditions in aquick and ideally selective manner.

Per the 2017 edlition of NFPA 70: National Electrical Code 250.4(A)(1) Electrical System Grounding“Electrical systems that are grounded shall be connected to earth ina manner that will limit the voltage imposed by lightningline surges or unintentional contact with higher-voltage lines and that will stabilize the voltage to earth during nor-mal operation."

Ground fault protection for specific equipment such as generatorstransformers ormotors is worthy of several articles and will only be discussed tangentially here. Un-less noted otherwiseall discussion of ground fault protection applies primarily to the

protection needed? Whyis ground fault

coordination of distributionprotective devices.

STI Valued PartnershipsWhat tolook forinNFPA72-2022

Groundas defined inthe NECis the earth. Aground-fault occurs when aconductor at a voltage oth-er than the earth referencees into contact withanother conductive material connected to ground.Depending on the type ofgrounding system installed this can lead to transient or

Firestopping in Mass TimberConstruction

How smart buildings bat

health concerns

NEC changes enhanceresiliency

Designing an emergencypower supply system

Figure 1: This is a switchgear installation withcircuit breakers having phase- and ground faultprotection capabilities. Courtesy: CDM Smith

sustained overvoltagesundervoltages and un- desirable single-line-to-ground fault currents.If not isolatedthese faults can harm personnel

and damage to systems or even propagate into faults of higher magnitude.

It should be noted that an effective ground-fault current path’s primary purpose is tokeep noncurrent-carrying conductive materials as close to the system ground potentialas possible and to provide a safe path for ground-fault current in the event of a fault.

Howeverthe absence of an equipment grounding conductorwhich is part of the ef-fective ground-fault current pathdoes not mean an electrical system is ungroundled orthat ground fault protection cannot be used. The zero-sequence impedance of a set of

protection needed? Why is ground fault

conductors is impacted by several factors including conductor arrangementpresenceof groundling paths (equipment grounding conductorcable shieldsparallel paths etc.) and the surroundling environment.

STI Valued PartnershipsWhat tolook forinNFPA72-2022

Groundingstandardsandcodes

All electrical designs or construction must adhere to applicable standards and codes.The following are some of the items that relate to grounding and bonding of electricalsystems and ground fault protection requirements:

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How smart buildings bathealth concerns

Article 250: Grounding and Bonding● Article 250.4: General Requirements for Grounding and Bonding.●Article 250.20: Alternating-Current Systems to be Groundled.●Article 250.130: Equipment Grounding Conductor Connections.

NEC changes enhanceresiliency

Designing an emergencypower supply system

● Article 230.95: Ground fault protection of Equipment for Services.● Article 215.10: Ground fault protection of Equipment for feeders.● Article 240.13: Ground fault protection of Equipment.● Occupational Safety and Health Administration Standard 1910.304: Wiring Design ● NFPA 780: Standard for the Installation of Lightning Protection Systems.and Protection.●OSHA Standard 3007: Ground Fault Protection on Construction Sites.

Groundingsystemtypes

The term grounded or grounding is often loosely used in the industry. Groundingperthe 2017 NECis the connection to ground or to a conductive body that extends theground connection. Grounding includes both equipment and systems. Equipment