Overview

Electrical safety is an important issue for those working on electrical facilities in utility networks and large industrial installations. A number of serious accidents including fatalities occur every year due to accidents involving electricity resulting in huge financial losses and wasted man-hours. Arc flashes in electrical equipment are now considered one of the major causes of electrical accidents even surpassing the well known hazards of electric shock. Avoiding arc flash incidents and the resulting injuries is one of major challenges today facing electrical workers and requires adequate attention in the stages of system planning, design, installation, operation and maintenance.

Injuries due to arc flash can depend on many factors, one of which is the incident thermal energy on a worker exposed to a flash. Today, a considerable body of knowledge exists as a result of research efforts and is available to designers and maintenance engineers in the form of standards such as IEEE 1584 and NFPA 70E. T his program will detail the basis of this approach and also about the major advances that have been made in the area of PPE made of FR fabrics and rated for different levels of thermal exposure.

Prevention however still remains the best form of protection and switchgear manufacturers have made considerable design advances to ensure that the effect of arc flash incidents is contained within the enclosure of switchgear (often called arc flash resistant switchgear) and methods of testing such switchgear have also evolved simultaneously. Another important factor is the approach to avoid arc incidents within the switchgear by proper design and maintenance and techniques to reduce the severity of the flash should such incidents occur.

These would form the key focus areas of this course.

By the end of this Professional Development course you will be able to:

  • Identify the important hazards in O&M work in different parts of electrical installations
  • Recognise the dangers of arc flash events to working personnel and their impact on equipment
  • Know the codes and standards dealing with arc flash danger
  • Acquire the necessary theoretical knowledge to carry out arc flash impact studies by collecting system data and computing the arc flash incident energy and flash protection boundary
  • Understand the importance of proper design of electrical equipment in avoiding arc flash incidents and ensuring safety in the event of an arc flash

Select appropriate Personal Protective Equipment (PPE) and Flame Resistant (FR) clothing required for avoiding serious or lethal injuries

Course Outline

MODULE 1: ELECTRICAL HAZARDS

Hazards with examples: electric shock, arc flash events, working at heights, working in confined spaces, fire and explosion, mechanical hazards
Common electrical equipment and hazards posed

MODULE 2: ARC FLASH AND ITS EFFECTS

Definitions
Reasons for arc flash events
What really happens in an arc flash event?

  • Insulation failure/violation of clearances
  • Arc flash mechanism

Impact on equipment
Hazards to personnel in the vicinity

  • Burns
  • Organ damage due to pressure wave
  • Hearing damage
  • Shrapnel effects

MODULE 3: FUNDAMENTALS OF POWER SYSTEMS

Configurations
Equipment used
System earthing and its role
Protective earthing and its role
Faults and types of faults
Bolted faults and arc faults

MODULE 4: CALCULATION OF FAULT CURRENTS

Fundamentals of short circuit calculations
Simplifying assumptions
Ohmic impedance and per unit impedance
Infinite bus
Base KVA of a system and its use in calculations
Network theorems commonly used
Equivalent diagrams
Fault calculation approach for a simple system
Earth faults and the importance of system earthing
Mitigation of fault levels in a system

MODULE 5: PROTECTION IN POWER SYSTEMS

Fundamentals of power system protection
Protection attributes
Protective devices (fuses, built-in release and relays)
Time-current characteristics
Impact of bolted faults on tripping time
I2t: the important factor in deciding the hazards of faults
Commonly used protection approaches

MODULE 6: ARC FLASH STUDIES – CODES AND STANDARDS

OSHA 29 C FR – part 1910
National Electrical Code N FPA 70E – standard for electrical safety in the workplace

  • Safety related work practices
  • Installation safety requirements
  • Table 130.2(C

IEEE Standard 1584

  • Guide for arc flash hazard analysis

Definitions used in arc flash study

MODULE 7: ARC FLASH STUDY DETAILED PROCEDURE

Flash protection approach boundary

  • 1.2 calories per square centimetre
  •  4 foot boundary
  • Calculated boundaries based on transformer size and bolted short circuit MVA

Detailed arc flash study

  • Calculation of incident energy and flash boundaries
  • Warning labels
  • Personal protective equipment requirements

Calculation of working distance and flash boundary as per IEEE Standard 1584

MODULE 8: DATA COLLECT ION AND SYSTEM MODELING

Data for calculation of fault currents
Modes of operation
Lower short circuit conditions with long tripping times

MODULE 9: DETERMINING ARC FLASH HAZARD RISK CATEGORY

Detailed examples and exercises simplified tables approach
Matrix table
Single line diagram approach
Short circuit study report coordination
Hazard risk category for metal clad switchgear 1kv and above
NFPA 70E table 130

MODULE 10: REDUCING ARC-FLASH HAZARD

Mitigation of energy by reduced short circuit current and faster protection
Overvoltage protection to reduce insulation failure risk
Reducing the risk of arc flash by better equipment design (clearances, creepage, insulation)
Providing arc vents to direct arc away from operator
Containing internal arc flash by switchgear that is arc resistance
Avoid local operations and live work
Better maintenance practices

  • Insulation status and PD monitoring
  • Contacts and joint status-monitoring through thermography

MODULE 11: PERSONAL PROTECTIVE EQUIPMENT MADE OF FR CLOTHING

The evolution of Flame Resistant (FR) fabrics
The various types of FR fabrics that are available in the marketplace
FR fabrics and the effects of undergarments
Limitations of FR fabrics
Test method ASTM F 1959
Garment construction standard ASTM F 1506-02a

MODULE 12: Project Work

Apply the principles learnt and calculate the arc flash protection boundary and incident energy for a panel and prepare an arc flash label

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How can an e-learning course be interactive?

Boredom can be a real danger, however, we use an interactive approach to our e-Learning – with live sessions instead of recordings.  The webinar software allows everyone to interact and involves participants in group work; including hands-on exercises with simulation software and remote laboratories where possible.  You can communicate with text messages, or live VoIP speech, or can even draw on the whiteboard during the sessions.

 

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