FIREALARMTERMINALCABINET
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 protection ground faults actuallypresent a far more mon and - in aggregate - potentially more dangerous occur-rence for personnel and equipment. Grounding bonding 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 lightning line 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 generators transformers ormotors is worthy of several articles and will only be discussed tangentially here. Un-less noted otherwise all discussion of ground fault protection applies primarily to the
protection needed? Whyis ground fault
coordination of distributionprotective devices.
STI Valued PartnershipsWhat tolook forinNFPA72-2022
Ground as defined inthe NEC is 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 overvoltages undervoltages and un- desirable single-line-to-ground fault currents.If not isolated these 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.
However the absence of an equipment grounding conductor which is part of the ef-fective ground-fault current path does 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 arrangement presenceof groundling paths (equipment grounding conductor cable shields parallel 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:
Firestopping in Mass TimberConstruction
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. Grounding perthe 2017 NEC is the connection to ground or to a conductive body that extends theground connection. Grounding includes both equipment and systems. Equipment
