“Electrical Safety in the Workplace”
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Is Anyone Doing an Arc Flash Analysis?
Get your FREE subscription PRINT or DIGITAL page 33 A CLB MEDIA INC. PUBLICATION • OCTOBER 2009 • VOLUME 45 • ISSUE 9 T&B_lug_EB_Oct09.indd 1 9/30/09 11:09:38 AM In the rush to label everything, is anyone doing an arc flash analysis? Also in this issue... • LED parking lot lighting (Page 7) • WorldSkills 2009 wrap-up (Page 16) • New guy on the block: PM # 40063602 The Running Man (Page 25) Nexans_EB_Oct09.indd 1 10/7/09 1:20:10 PM EB_Oct09_1-22.indd 1 10/13/09 2:34:26 PM Standard_EB_Oct09.inddEB_Oct09_1-22.indd 2 1 9/29/0910/6/09 2:06:3512:50:25 PM PM lectrical FROM THE EDITOR E usiness THE AUTHORITATIVE VOICE OF BCANADA’S ELECTRICAL INDUSTRY Putting smart grid October 2009 • Volume 45 • Issue 9 into better perspective am officially declaring that ‘smart grid’ should no longer be and the wind isn’t always blowing! We need to infuse our electrical spelled with any capitalization. Although IEC and NEMA infrastructure with the intelligence it needs to monitor, measure, ELECTRICAL BUSINESS is the magazine of the Canadian electrical I continue to capitalize the thing, I believe this just makes bill, etc., electricity from all kinds of other sources, as well as be able industry. It reports on the news and publishes articles in a manner the whole notion a little too high-and-mighty for my liking. to ramp up tried-and-true standby methods (like hydro, nuclear, that is informative and constructive. It’s time smart grid was brought down from the 30,000-ft etc.) when shortfalls are anticipated. -
2020 National Electrical Code® Style Manual
2020 NATIONAL ELECTRICAL CODE® STYLE MANUAL 1 FOREWORD August 2020 The National Electrical Code® is used nationally and internationally as the basis for safeguarding persons, buildings, and their contents from hazards arising from the use of electricity. It is vitally important that the text be as explicit as possible, and that maximum consistency be achieved in the language used in the text. The Code contains those provisions considered necessary for safety and thus is widely used as a basis for legal enforcement in the installation of electrical conductors and equipment in buildings and certain other premises (as detailed in the Code itself); this places a major responsibility on those involved in the preparation of document text to use forms of expression that promote uniform interpretation. The National Electrical Code Correlating Committee has recognized these responsibilities and has issued this manual. Preparation and Date of Adoption. This manual was originally prepared by the Editorial Task Group of the National Electrical Code Committee and adopted by the National Electrical Code Correlating Committee on May 13, 1969. It was amended September 22, 1975, October 11, 1984, October 12, 1989, and May 9, 1994. In January 1999, the Correlating Committee Task Group on the Usability of the NEC rewrote the manual. It was adopted by the National Electrical Code Correlating Committee on March 19, 1999 and by the Standards Council on April 15, 1999. It was amended March 1, 2001, January 15, 2003, and August 9, 2011, August 2015, and December 2020. 2 TABLE OF CONTENTS Foreword ........................................................................................................ 2 Chapter 1 General 4 1.1 Purpose ............................................................................................ -
Work and Energy Summary Sheet Chapter 6
Work and Energy Summary Sheet Chapter 6 Work: work is done when a force is applied to a mass through a displacement or W=Fd. The force and the displacement must be parallel to one another in order for work to be done. F (N) W =(Fcosθ)d F If the force is not parallel to The area of a force vs. the displacement, then the displacement graph + W component of the force that represents the work θ d (m) is parallel must be found. done by the varying - W d force. Signs and Units for Work Work is a scalar but it can be positive or negative. Units of Work F d W = + (Ex: pitcher throwing ball) 1 N•m = 1 J (Joule) F d W = - (Ex. catcher catching ball) Note: N = kg m/s2 • Work – Energy Principle Hooke’s Law x The work done on an object is equal to its change F = kx in kinetic energy. F F is the applied force. 2 2 x W = ΔEk = ½ mvf – ½ mvi x is the change in length. k is the spring constant. F Energy Defined Units Energy is the ability to do work. Same as work: 1 N•m = 1 J (Joule) Kinetic Energy Potential Energy Potential energy is stored energy due to a system’s shape, position, or Kinetic energy is the energy of state. motion. If a mass has velocity, Gravitational PE Elastic (Spring) PE then it has KE 2 Mass with height Stretch/compress elastic material Ek = ½ mv 2 EG = mgh EE = ½ kx To measure the change in KE Change in E use: G Change in ES 2 2 2 2 ΔEk = ½ mvf – ½ mvi ΔEG = mghf – mghi ΔEE = ½ kxf – ½ kxi Conservation of Energy “The total energy is neither increased nor decreased in any process. -
90 INTRODUCTION to the National Electrical Code
ARTICLE INTRODUCTION TO THE 90 NATIONAL ELECTRICAL CODE Introduction to Article 90—Introduction to the National Electrical Code Many NEC violations and misunderstandings wouldn’t occur if people doing the work simply understood Article 90. For exam- ple, many people see Code requirements as performance standards. In fact, the NEC requirements are bare minimums for safety. This is exactly the stance electrical inspectors, insurance companies, and courts take when making a decision regard- ing electrical design or installation. Article 90 opens by saying the NEC isn’t intended as a design specification or instruction manual. The National Electrical Code has one purpose only, and that’s the “practical safeguarding of persons and property from hazards arising from the use of electricity.” The necessity of carefully studying the NEC rules can’t be overemphasized, and the role of textbooks such as this one is to help in that undertaking. Understanding where to find the rules in theCode that apply to the installation is invaluable. Rules in several different articles often apply to even a simple installation. Article 90 then describes the scope and arrangement of the NEC. The balance of this article provides the reader with informa- tion essential to understanding the Code rules. Typically, electrical work requires you to understand the first four chapters of theNEC which apply generally, plus have a working knowledge of the Chapter 9 tables. That understanding begins with Article 90. Chapters 5, 6, and 7 make up a large portion of the Code, but they apply to special occupancies, special equipment, or other special conditions. -
Multidisciplinary Design Project Engineering Dictionary Version 0.0.2
Multidisciplinary Design Project Engineering Dictionary Version 0.0.2 February 15, 2006 . DRAFT Cambridge-MIT Institute Multidisciplinary Design Project This Dictionary/Glossary of Engineering terms has been compiled to compliment the work developed as part of the Multi-disciplinary Design Project (MDP), which is a programme to develop teaching material and kits to aid the running of mechtronics projects in Universities and Schools. The project is being carried out with support from the Cambridge-MIT Institute undergraduate teaching programe. For more information about the project please visit the MDP website at http://www-mdp.eng.cam.ac.uk or contact Dr. Peter Long Prof. Alex Slocum Cambridge University Engineering Department Massachusetts Institute of Technology Trumpington Street, 77 Massachusetts Ave. Cambridge. Cambridge MA 02139-4307 CB2 1PZ. USA e-mail: [email protected] e-mail: [email protected] tel: +44 (0) 1223 332779 tel: +1 617 253 0012 For information about the CMI initiative please see Cambridge-MIT Institute website :- http://www.cambridge-mit.org CMI CMI, University of Cambridge Massachusetts Institute of Technology 10 Miller’s Yard, 77 Massachusetts Ave. Mill Lane, Cambridge MA 02139-4307 Cambridge. CB2 1RQ. USA tel: +44 (0) 1223 327207 tel. +1 617 253 7732 fax: +44 (0) 1223 765891 fax. +1 617 258 8539 . DRAFT 2 CMI-MDP Programme 1 Introduction This dictionary/glossary has not been developed as a definative work but as a useful reference book for engi- neering students to search when looking for the meaning of a word/phrase. It has been compiled from a number of existing glossaries together with a number of local additions. -
Arc Flash Resistant Equipment
Arc Flash Resistant Equipment Course No: E02-019 Credit: 2 PDH Velimir Lackovic, Char. Eng. Continuing Education and Development, Inc. 22 Stonewall Court Woodcliff Lake, NJ 07677 P: (877) 322-5800 [email protected] ARC FLASH RESISTANT EQUIPMENT Arc flash resistant equipment may be described as the equipment made to withstand the impact of internal arcing fault by meeting the testing requirements of IEEE Guide C37.20.7-2007. In the 1970s, an interest started in Europe in assessing electrical equipment under internal arcing, which led to the IEC standard. This research spread through North America and was used as a foundation for the EEMAC G14-1 procedure. The development of the IEEE standard heavily relies on Annex AA of the IEC standard and adopts many of the refinements originated in the EEMAC G14-1 procedure. IEC 62271 - 200 defines the requirements for factory assembled metal- enclosed switchgear and control gear for alternating currents at a rated voltage above 1 kV and up to and including 52 kV. It includes indoor and outdoor assemblies and frequencies up to and including 60 Hz. The arc-resistant construction can be used for: - Medium voltage switchgear - Low voltage switchgears - Medium voltage MCCs - Low voltage MCCs. ARC FLASH HAZARD CALCULATION IN ARC-RESISTANT DEVICES It is well known that even if arc-resistant devices are used, additional power system protection, like AFD and differential protection systems, need to be provided to decrease the arcing time and incident energy release. The computation of incident energy, hazard risk category and PPE category for arc-resistant devices and their reductions uses the same methodology as for typical electrical equipment. -
Introduction to Electrical and Computer Engineering International
Introduction to Electrical and Computer Engineering Basic Circuits and Simulation Electrical & Computer Engineering Basic Circuits and Simulation (1 of 22) International System of Units (SI) • Length: meter (m) • SI Prefixes (power of 10) • Mass: kilogram (kg) – 1012 Tera (T) • Time: second (s) – 109 Giga (G) – 106 Mega (M) • Current: Ampere (A) – 103 kilo (k) • Voltage: Volt (V) – 10-3 milli (m) • Temperature: Degrees – 10-6 micro (µ) Kelvin (ºK) – 10-9 nano (n) – 10-12 pico (p) Electrical & Computer Engineering Basic Circuits and Simulation (2 of 22) 1 SI Examples • A few examples: • 1 Gbit = 109 bits, or 103106 bits, or one thousand million bits – 10-5 s = 0.00001 s; use closest SI prefix • 1×10-5 s = 10 × 10-6 s or 10 μs or • 1×10-5 s = 0.01 × 10-3 s or 0.01 ms Electrical & Computer Engineering Basic Circuits and Simulation (3 of 22) Typical Ranges Voltage (V) Current (A) • 10-8 Antenna of radio • 10-12 Nerve cell in brain receiver (10 nV) • 10-7 Integrated circuit • 10-3 EKG – voltage memory cell (0.1 µA) produced by heart • 10×10-3 Threshold of • 1.5 Flashlight battery sensation in humans • 12 Car battery • 100×10-3 Fatal to humans • 110 House wiring (US) • 1-2 Typical Household • 220 House wiring (Europe) appliance • 107 Lightning bolt (10 MV) • 103 Large industrial appliance • 104 Lightning bolt Electrical & Computer Engineering Basic Circuits and Simulation (4 of 22) 2 Electrical Quantities • Electric Charge (positive or negative) – (Coulombs, C) - q – Electron: 1.602 x 10 • Current (Ampere or Amp, A) – i or I – Rate of charge flow, – 1 1 Electrical & Computer Engineering Basic Circuits and Simulation (5 of 22) Electrical Quantities (continued) • Voltage (Volts, V) – w=energy required to move a given charge between two points (Joule, J) – – 1 1 1 Joule is the work done by a constant 1 N force applied through a 1 m distance. -
Kinetic Energy and Work
Kinetic Energy and Work 8.01 W06D1 Today’s Readings: Chapter 13 The Concept of Energy and Conservation of Energy, Sections 13.1-13.8 Announcements Problem Set 4 due Week 6 Tuesday at 9 pm in box outside 26-152 Math Review Week 6 Tuesday at 9 pm in 26-152 Kinetic Energy • Scalar quantity (reference frame dependent) 1 K = mv2 ≥ 0 2 • SI unit is joule: 1J ≡1kg ⋅m2/s2 • Change in kinetic energy: 1 2 1 2 1 2 2 2 1 2 2 2 ΔK = mv f − mv0 = m(vx, f + vy, f + vz, f ) − m(vx,0 + vy,0 + vz,0 ) 2 2 2 2 Momentum and Kinetic Energy: Single Particle Kinetic energy and momentum for a single particle are related by 2 1 2 p K = mv = 2 2m Concept Question: Pushing Carts Consider two carts, of masses m and 2m, at rest on an air track. If you push one cart for 3 seconds and then the other for the same length of time, exerting equal force on each, the kinetic energy of the light cart is 1) larger than 2) equal to 3) smaller than the kinetic energy of the heavy car. Work Done by a Constant Force for One Dimensional Motion Definition: The work W done by a constant force with an x-component, Fx, in displacing an object by Δx is equal to the x- component of the force times the displacement: W = F Δx x Concept Q.: Pushing Against a Wall The work done by the contact force of the wall on the person as the person moves away from the wall is 1. -
Feeling Joules and Watts
FEELING JOULES AND WATTS OVERVIEW & PURPOSE Power was originally measured in horsepower – literally the number of horses it took to do a particular amount of work. James Watt developed this term in the 18th century to compare the output of steam engines to the power of draft horses. This allowed people who used horses for work on a regular basis to have an intuitive understanding of power. 1 horsepower is about 746 watts. In this lab, you’ll learn about energy, work and power – including your own capacity to do work. Energy is the ability to do work. Without energy, nothing would grow, move, or change. Work is using a force to move something over some distance. work = force x distance Energy and work are measured in joules. One joule equals the work done (or energy used) when a force of one newton moves an object one meter. One newton equals the force required to accelerate one kilogram one meter per second squared. How much energy would it take to lift a can of soda (weighing 4 newtons) up two meters? work = force x distance = 4N x 2m = 8 joules Whether you lift the can of soda quickly or slowly, you are doing 8 joules of work (using 8 joules of energy). It’s often helpful, though, to measure how quickly we are doing work (or using energy). Power is the amount of work (or energy used) in a given amount of time. http://www.rdcep.org/demo-collection page 1 work power = time Power is measured in watts. One watt equals one joule per second. -
Electric Potential
Electric Potential • Electric Potential energy: b U F dl elec elec a • Electric Potential: b V E dl a Field is the (negative of) the Gradient of Potential dU dV F E x dx x dx dU dV F UF E VE y dy y dy dU dV F E z dz z dz In what direction can you move relative to an electric field so that the electric potential does not change? 1)parallel to the electric field 2)perpendicular to the electric field 3)Some other direction. 4)The answer depends on the symmetry of the situation. Electric field of single point charge kq E = rˆ r2 Electric potential of single point charge b V E dl a kq Er ˆ r 2 b kq V rˆ dl 2 a r Electric potential of single point charge b V E dl a kq Er ˆ r 2 b kq V rˆ dl 2 a r kq kq VVV ba rrba kq V const. r 0 by convention Potential for Multiple Charges EEEE1 2 3 b V E dl a b b b E dl E dl E dl 1 2 3 a a a VVVV 1 2 3 Charges Q and q (Q ≠ q), separated by a distance d, produce a potential VP = 0 at point P. This means that 1) no force is acting on a test charge placed at point P. 2) Q and q must have the same sign. 3) the electric field must be zero at point P. 4) the net work in bringing Q to distance d from q is zero. -
Industrial MI Wiring Cable
Industrial MI Wiring Cable Installation Manual for Alloy 825 Sheath Cable Wiring Systems Important Safeguards and Warnings WARNING: FIRE AND SHOCK HAZARD. nVent PYROTENAX mineral insulated (MI) industrial wiring cables must be installed in accordance with the requirements of national and local codes and standards, the installation instructions in this manual, and the customer’s specification. Read these important safeguards and carefully follow the installation instructions. • Ensure the cable has been stored properly and is in good condition prior to commencing installation. • Always use safe working practices when installing cables, observing OSHA and other national safety rules. • Store cables indoors in a clean, dry, covered area, if possible. • During the time that the cables are exposed and during cable pulling activities, protect cables from nearby or overhead work to prevent damage to the cable sheath. • Do not pull cables around corners that have sharp edges, such as corners in cable trays, or other obstructions. • Prevent damage to cables by removing any abrasions or sharp edges from surface of support system. • Damage to cables or components can cause sustained electrical arcing or fire. Do not energize cables that have been damaged. Damaged cable or terminations may need to be repaired or replaced. Damaged cable should be repaired by a qualified person. • When installing cables which may be exposed to hydrocarbon flash fires, use only steel or stainless steel in the support system. ii | nVent.com Table of Contents General Information -
Maximum Frictional Dissipation and the Information Entropy of Windspeeds
J. Non-Equilib. Thermodyn. 2002 Vol. 27 pp. 229±238 Á Á Maximum Frictional Dissipation and the Information Entropy of Windspeeds Ralph D. Lorenz Lunar and Planetary Lab, University of Arizona, Tucson, AZ, USA Communicated by A. Bejan, Durham, NC, USA Registration Number 926 Abstract A link is developed between the work that thermally-driven winds are capable of performing and the entropy of the windspeed history: this information entropy is minimized when the minimum work required to transport the heat by wind is dissipated. When the system is less constrained, the information entropy of the windspeed record increases as the windspeed ¯uctuates to dissipate its available work. Fluctuating windspeeds are a means for the system to adjust to a peak in entropy production. 1. Introduction It has been long-known that solar heating is the driver of winds [1]. Winds represent the thermodynamic conversion of heat into work: this work is expended in accelerat- ing airmasses, with that kinetic energy ultimately dissipated by turbulent drag. Part of the challenge of the weather forecaster is to predict the speed and direction of wind. In this paper, I explore how the complexity of wind records (and more generally, of velocity descriptions of thermally-driven ¯ow) relates to the available work and the frictional or viscous dissipation. 2. Zonal Energy Balance Two linked heat ¯uxes drive the Earth's weather ± the vertical transport of heat upwards, and the transport of heat from low to high latitudes. In the present paper only horizontal transport is considered, although the concepts may be extended by analogy into the vertical dimension.