University of Lagos

School of Postgraduate Studies

Department of Electrical/Electronics
Engineering

Ph.D Research Seminar Presentation:

Seminar I: Study of Power System Security - Arc
Flash Threats

PRESENTER:
Eruotor, Francis Ogheneakpobo
(Matric No.: 099043093)

SUPERVISORS:
Dr. T. O. Akinbulire (Ass. Prof.)
Dr. P. O. Oluseyi
Prof. C. O. A Awosope (Rtd)

Date: Thursday, March 29, 2017.

Venue: Seriki Library (High Voltage Building)
Time: 10:00am

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Abstract

Arc flash events have resulted in several accidents due to faults in electrical

equipment that resulted in a significant release of energy. This event is a hazard

and threat to the Power System Security and due to the large energy release,

plasma is generated, as pressure increases since it causes physical damage to

equipment while life of system operators within the vicinity of its occurrence are at

risk. Although arc flash is one of the electrical safety programs that have been in

existence, arc flash hazard was not adequately addressed until recently. However,

the Electric Arc phenomenon is relatively new in the Nigerian power industry, there

are certain aspect that are yet to be treated by the available literature, hence it is

the duty of this work to establish model for addressing the observed lapses. The

design is adequately prepared for the power system security analysis using typical

scenarios in industrial facilities that are prone to yield high incident energy levels. In

line with the foregoing, the developed methodology is validated using a segment of

the Nigeria’s power industry as case study.

Keywords: Arc Flash, Bolt Fault, Short Circuit, Power-flow, System Design, Incident
Energy, Protection.

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1.0 Introduction

1.1 Background of the Study

In October 1878 a power source of electricity for lighting was created by

Thomas Edison. This invention of the light bulb is supplied with the direct

current to generate illumination. This was the advent of electrical energy

generation industry. It is essential to note that Edison did not only invented

the light bulb, but about a great deal of other electrical facilities or ancillaries

such as the distribution network, switches, protective fuses and insulating

materials. This was soon followed by the invention of the first highly successful

three-phase cage induction motor by Michael Dolivo-Dobrowolsky in 1889 which

rapidly increased the demand on the power system. Between 1885 and

1889, Nikola Tesla, George Westinghouse and others invented the three-

phase electric power system which was technically superior, since it was able

to be transformed to different voltages for transmission (Philips, 2009).

Immediately as a follow-up to these expeditions was formation of electrical

circuits, systems and networks. Thus accompanying the discovery and

installation of electrical systems is the electrical shock from commercial

electrical power system. This event spurred or initiated the development of

electrical safety codes & standards.

Thus, an arc flash occurs when electric current flows through the air instead of

its intended path. This results in an extremely high heat dissipation that

causes severe burns, blinding light, as well as a deafening explosion causing

bodily injury. Arc flash temperatures can reach or exceed 35,000 °F

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 (19,400 °C) at the arc terminals (Kowalski-Trakofler, et al, 2013, Rockwell,

2005). The massive energy released in the fault rapidly vaporizes the metal

conductors involved, blasting molten metal and expanding plasma outward

with extraordinary force (Kowalski-Trakofler, et al, 2013). A typical arc flash

incident can be inconsequential but could conceivably easily produce a more

severe explosion. The result of the violent event can cause destruction of

power equipment, fire outbreak as well as injury; not only to an electrical

worker but also to people in the vicinity of the event. During the arc flash

event, electrical energy intensity melts metallic objects in the switch contacts

which changes from solid state to gas vapor, expanding it with explosive

force. For instance, when copper vaporizes it suddenly expands by a factor of

67,000 times in volume (Jones, et al, 2000, Rockwell, 2005). This is the

phenomenon of Arc Flash Explosion.

There has been very few quality research in this area. Thus the study of the

Arc Flash Explosion Protection is essential for ensuring that he Power System

needs to be operationally secure, i.e. with minimal probability of blackout and

equipment damage.

Currently the situations of power security in the industry are captured below

since electrical injuries represent a serious workplace health and safety issue.

Data from the U.S. Bureau of Labor Statistics (BLS) indicates that there were

nearly 6,000 fatal electrical injuries to workers in the U.S. between 1992 and

2013 (Campbell, et al, 2015). BLS data also indicates that there were 24,100

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 non-fatal electrical injuries from 2003 through 2012, the most recent 10-year

period for which data is available (Campbell, et al, 2015). In Germany alone,

about 600 electrical accidents are reported each year (Picard, C. et al, 2001).

Almost 25% of those accidents are related to the arc-fault incidents, often with

severe burns on the hands and the face, sometimes fatal (Picard, C. et al, 2001).

It is noted that more than 50% of all electrical incidents with over 90% of all arc flash

incidents happen is accounted for by Low Voltage switchgear (Picard, C. et al,

2001).

It is also useful to look at injury data by occupation, since each industry

encompasses a number of employees performing different work tasks. Fig 1

shows the total number of work- related electrical fatalities from 2004 to 2013 as

classified by occupation.

Fatalities by Occupation, 2004-2013.

Construction
9%
Professional & business
11% services
Trade, transportation &
12% utilities
53%
Natural resources &
mining
15%
Manufacturing

Figure 1 - Work-Related Electrical Fatalities by Occupation, 2004-2013.

(Campbell, et al, 2015)

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 In addition to the explosive blast, called the arc blast of such a fault,

destruction also arises from the intense radiant heat produced by the arc. The

metal plasma arc produces tremendous amounts of light energy from far

infrared to ultraviolet. Surfaces of nearby objects, including people, absorb

this energy and are instantly heated to vaporizing temperatures. The effects of

this can be seen on adjacent walls and equipment - they are often ablated

and eroded from the radiant effects. The radiant energy released by an

electric arc is capable of permanently injuring or killing a human being at

distances of up to 20 feet (6.1 m) while Fatal burns can occur when the victim

is several feet from the arc. Serious burns are common at a distance of 10

feet. Staged tests have shown temperatures greater than 437°F (225°C) on

the neck and hands of a person standing close to an arc blast (Rockwell,

2005; Campbell, 2015).

Meanwhile, some of the efforts that have been previously made by

researchers on this subject are evaluated below:

It has become apparent that not all electrical accidents are due to electrical

shock from making contact with energized devices. When an exposed

energized conductor makes contact with the ground or another energized

device, a small spark or a large explosion could ignite. This explosion,

otherwise known as an arc flash, can have thermal energy that is dangerous

from a distance of several feet away. One of the early works addressing the

arc flash phenomenon was written in 1982 by Ralph Lee (Lee, 1982). This

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 work established a nexus between electrical shocks from contact with

energized devices, to thermal burn from the radiant heat output of electrical

arcs. Though, this research effort presented theoretical methods for

evaluating incident energy of an arc in open air by advancing a relationship

on heat transfer philosophy as well as the measurement of distance of human

safety. But the work did not capture the option of High-resistance grounding to

reduce the chances of arc-flash hazard and downtime

Additionally, Lee’s research explained the relationship between heat transfer

from hotter to cooler objects and the importance of the distance between them.

Lee’s work goes on to develop a relationship between heat transfer and

distance with its effects on human skin tissue.

Throughout the years, people learned that electrical shock could cause

serious injury and e v e n death. However, there was very little knowledge

on the effects of electrical shock on humans. It was not until 1956 that

Charles Dalziel began performing shock experiments on animals and

humans. His quest to find out how much electrical current was needed to

stop a person from breathing or to stop a heart from working led to the

information in Table 1 (Dalziel, 1956). The work of Charles Dalziel drew

human attention to the risk of small amounts of electricity and increased

safety awareness.

Table 1: Reaction of Human Body to Electric Current

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 AC Current Effect of Current

0.7 – 1 mA Perception Threshold (tingling sensation)

1.2 – 1.8 mA Slight Shock – not painful

6 – 9 mA Shock – painful (no loss of muscle control)

Shock – severe (muscle control loss, breathing
15 – 23 mA difficulty)

0.1 A Possible ventricular fibrillation (3-second shock)

0.2 A Possible ventricular fibrillation (1-second shock)

0.5 A Heart muscle activity ceases

1.5 A Tissue and organ burn

The industrial revolution from 1950 to 1970 created enormous growth in the

United States. With this expansion came many workplaces with little concern

for employee safety. Based on Occupational Safety and Health Administration

(OSHA) statistics from 1970, there were 14,000 worker deaths that year from

job related accidents (Philips, 2005). Close to 2.5 million workers would

become disabled and 300,000 individuals would contact an occupational

disease (Philips, 2005). This prompted the US Congress to pass the

Occupational Safety and Health Act of 1970, leading to the formation of the

Occupational Safety and Health Administration (OSHA).

In 1998, Doughty, Neal, and Floyd did extensive research on the measurement

and calculation of arc flash (Doughty,et al, 1998). The research detailed a

testing program completed to measure incident energy from 6-cycle arcs on

600 volt power systems. The testing led to algorithms for predicting incident

energy based on available fault current and the distance from the source.
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 These algorithms were shown to support Ralph Lee’s research. However, this

testing also showed an increase in incident energy when the source is in an

enclosure with an open door versus a source in open air, such as an overhead

conductor. This proved important because most arcs occur when a person is

standing in front of an open electrical enclosure and the arc is confined in the

panel-board or switchgear. This work could not consider the possibilities of

introducing arc-venting capabilities (The Plenum Solution) to evacuate arc cute

outside the building.

In 2000, the NFPA released a new version of NFPA 70E. This update

recognized the existence of the “Arc Flash Hazard” and included a new

protection strategy in addition to shock protection. There was now a section on

Personal Protection Equipment (PPE) requirements and hazard risk tables.

This standard identified specific electrical work activities and put them in five

categories (0-4). Each category had a detailed clothing arc flash rating and

additional equipment to be worn, such as hard hats and facemasks. However,

this method of selecting protective equipment was based solely by task and not

on actual knowledge of the arc flash hazard level at any location in the electrical

system.

The findings detailed above, along with the focus of industry on electrical safety,

led to the need for guidelines and standards addressing the arc flash. In 2002,

The Institute of Electrical and Electronics Engineers published Standard 1584

“IEEE Guide for Performing Arc-Flash Hazard Calculations” (IEEE Std 1584,

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 2002). This guide was a direct result of research conducted by the IEEE and

was sponsored by large electrical corporations and manufacturers. The standard

provided the first complete set of guidelines for calculating incident energy of the

arc flash at the location of interest in a power distribution system. This was

important because it provided a standardized way to calculate the arc flash

hazard associated with working on energized equipment.

1.2 Significance of Study

As stated earlier, an arc flash is one of the major causes of explosion in

industries. Explosion which is due to arc flash results in death and injury to

workers. At the same time, it causes loss of production and downtime leading

to a huge economic loss for a country. Therefore, this work will help to reduce

harm or fatality in the power industries. Arc flash studies should be used to

determine the minimum level of Personal Protective Equipment (PPE) that

workers must wear when they are near exposed energized equipment.

Arc flash had several important consequences, the workers needed to know

what degree of potential electrical hazards they were being exposed to. The

focus of arc flash hazard research is aimed at predicting and calculating the

incident energy produced.

By utilizing the calculation method developed in this current research, an

engineer will adequately predict the thermal exposure at any location in an

electrical system. Thus the work would set a guideline for protection from
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 electrical shock and arc flash hazard. This is important because the shock

protection protective equipment is made from specific materials to keep a

person isolated from touching the energized equipment. The arc flash hazard

protective equipment is made of materials that are designed to protect the

worker from getting burned from the thermal effects of the arc flash.

So also in line with this, the other reasons to address Arc Flash Hazard are
primarily to:

• Protect workers from potential harm and prevent loss of life.

• Comply with Occupational Safety and Health Administration (OSHA)

codes and with National Fire Protection Association (NFPA) standards on

employee safety, NFPA-70E. This work will evaluate these codes and draw

up standards for Nigeria Power System Safety.

• Prevent loss to organizations through loss of skilled manpower, Asset,

litigation fees, higher insurance costs, and loss of morale.

• Reduce production downtime by reducing accidents.

1.3 Problems Statement

Electric arc flash is a serious hazard that workers in many industries face

every day. According to the Bureau of Labor Statistics, nonfatal electrical

injury most often occurs from contact with the electric circuitry of machines,

tools, appliances or light fixtures. Another leading cause is from contact with

energized equipment including transformers, motors and switchgear of

various voltage ratings.

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 In Nigeria, there are no known records or statistical database of effects of

Electrical Arc Flash Hazard. The problem of arc flash hazard has not be given

the desired attention in Nigeria, electric arc flash hazard are not published but

considered as non-recordable incident. As we know there are cases of either

electric shock or electrocution on daily basis. This thesis will address

problems associated with Electric Arc Flash in Nigeria power sector with

emphasis on the Oil & Gas industries.

In layman’s terms, an arc flash event typically involves a flash of bright light

accompanied by a blast of intense radiant heat, noise and, in extremely high

energy arcs, fragmented or molten metal. The temperature from an arc flash

explosion can exceed 35,000 degrees Fahrenheit (Davis, et al, 2003). The

heat and energy emitted can result in personal injury, fire and substantial

damage to equipment

In order for an arc flash event to occur, the electrical system must

operate outside of the operating parameters defined during design. This

can occur through four primary methods:

Human error: When an electrician or maintenance professional is attempting

a repair, mistakes can occur and if the system is energized an arc flash may

occur. These include dropping tools or parts, mistakenly contacting energized

equipment with tools, equipment, or cable, or during equipment installation

(Dugan, 2007).

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 Equipment Failure: Medium voltage switchgear is energized for significant

lengths of time and while there are no visibly moving parts, there are potential

sources for failures. Equipment needs to be monitored and maintained to

ensure problems are identified. This will be further explored in the prevention

section of this work (Dugan, 2007).

Insulation Breakdown: Equipment or cables insulation can breakdown

over time due to the heat and energy through the wire. This breakdown can

cause shorts potentially leading to arc flash. Preventative maintenance and

monitoring of the equipment prevents such problems (Dugan, 2007).

Continuous Electrical Faults: If a fault occurs on an electrical network it

causes stresses elsewhere that manifests as heat or rapid energy

fluctuations. If these faults are left uncorrected they can exasperate the

problem, which has the potential for an arc flash event (Dugan, 2007).

Arc flash is a major concern for many industries worldwide, but particularly

the power distribution industry with workers operating on and within close

proximity to live electrical assets. Arc incidents are often caused due to a

fault across phases or phases to earth either from mechanical failure,

protection failure or human error.

Other causes that could initiate Electric Arcs are as follows:

• Glow to arc discharge:

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 - Dust and impurities: Dust and impurities on insulating surfaces can

provide a path for current, allowing it to flashover and create arc

discharge across the surface. This can develop into greater arcs.

Fumes or vapor of chemicals can reduce the breakdown voltage of

air and cause arc flash.

- Corrosion: Corrosion of equipment parts can provide impurities on

insulating surfaces. Corrosion also weakens the contact between

conductor terminals, increasing the contact resistance through

oxidation or other corrosive contamination. Heat is generated on the

contacts and sparks may be produced, this can lead to arcing faults

with nearby exposed conductors of different phase or ground.

• Condensation of vapor and water dripping can cause tracking on the

surface of insulating materials. This can create a flashover to ground and

potential escalation to phase to phase arcing (Lee, 1987).

• Spark discharge:

- Accidental tou c hi ng : Accidental contact with live exposed parts can

initiate arc faults.

- Dropping tools: Accidental dropping of tools may cause momentary

short circuit, produce sparks and initiate arcs.

• Over-voltages across narrow gaps: When air gap between conductors of

different phases is very narrow (due to poor workmanship or damage of

insulating materials), arcs may strike across during over-voltages.

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 • Failure of insulating materials.

• Improperly designed or utilized equipment.

• Improper work procedures.

Figure 2 : (a) Arc blast in box (Neal, 2003) (b) Arcing fault in electrical panel
board

Hazards of Arcing Faults

Figure 3 : (a) Hand burned by arc flash (Ligget, 2003)

Some of the hazards of arcing faults are:

• Heat: Fatal burns can occur when the victim is several feet from the arc.
Serious burns are common at a distance of 10 feet. Staged tests have
shown temperatures greater than 437oF on the neck area and hands for a
person standing close to an arc blast (Jones, 2000).

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 • Objects: Arcs spray droplets of molten metal at high-speed pressure.
Blast shrapnel can penetrate the body.

• Pressure: Blast pressure waves have thrown workers across rooms and
knocked them off ladders. Pressure on the chest can be higher than 2000
lbs/ sq. ft. (Davis, et al, 2003).

• Clothing can be ignited several feet away. Clothed areas can be burned
more severely than exposed skin. (Davis, et al, 2003).

• Hearing loss from sound blast: The sound can have a magnitude as
high as 140 dB at a distance of 2 feet from the arc. (Davis, et al, 2003).

Probability of Survival: Injuries due to arc flash are known to be very severe.

According to statistics from the American Burn Association, the probability of

survival decreases with the increasing age of the arc flash burn victim.

Figure 4: Burn Injury Statistics - Probability of Survival (Source: American Burn

Association, 1991-1993 Study; Revised March 2002)

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1.4 Aim & Objectives of Study

The aim of this work is to design and model a system that is resistant to Arc

Flash Explosion in Electrical Power Systems with a view to avoid arc flash

related accidents in energy-intensive industries.

The prime objectives of this work are to:

a. Carry out an Assessment of Arc Flash hazard in Nigerian power sector

b. Model and Design of Arc Flash Resistance System using Electrical

Transient Analyzer Program (ETAP) software

c. Determine the feasibility of retro-fitting thermal monitoring (Optical Arc

Flash Protection) to electrical assets with the development of relevant

equations

d. Proffer a Protection Protocol against Arc Flash Explosion.

1.5 Justification of the Study

The scope of this work is limited to early detection and prediction of arc flash

explosion in Power Systems Installation. This shall be achieved by calculation

of short circuit, flash protective boundary and selection of suitable Personal

Protective Equipment (PPE) level

Incident Energy Reduction Techniques with Low-Voltage Power Circuit

Breakers applying optimal Time-Current Curve Selection. This method

consists of using the fastest practical time-current characteristic while

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 maintaining selective coordination with upstream and downstream protective

devices (Brown, et al, 2009).

The time-current curves of upstream protective devices are a major factor in

determining how long an arc-fault will last. An effort will be made to determine

the actual settings rather than relying on standard values, as these may cause

incident energy to vary greatly.

Another consideration when analyzing protective devices is that incident

energy depends on both fault current and time. Since protective devices are

slower at lower currents, minimum fault currents often pose the worst-case

arc flash scenario.

This research effort shall estimate arcing time duration from the protective

device characteristics and the contributing arc current passing through this

device for every branch that significantly contributes to the arc fault. Since we

are considering a range of arc currents instead of a single value, we need to

determine the trip time for each arc current value - the upper bound, the lower

bound and the value calculated from NFPA 70E or IEEE 1584 equations.

The thermal consequences of arcing (exhausted gases at high temperature)

are then limited by designing the inside of the switchgear so that the outlet of

gases takes place in the top part (over 2 m) and not at lower heights which

might be potentially dangerous for the operator (Cutsem, 1993)

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 A switchboard of this type shall have mainly two design characteristics:

• Non-propagation of the arc between two adjacent columns;

• Non-propagation of the arc between the compartment housing the bars

and that where the apparatus are installed.

The fulfilment of these requirements is the result of the internal division into

compartments of the switchboard. As a matter of fact this allows obtaining

internal “arc proof” subdivisions, that is cubicles or compartments where the

arc is confined in its place of occurrence, thus avoiding damages to adjacent

areas.

This research work shall employ the following as arc flash protection methods:

a. Arc flash prevention

b. Mechanical protection methods

• Arc-resistant switchgear
• Remote racking and operation.

c. Reduction of incident energy by limiting fault current

• Transformer sizing and current limiting reactors.
• Fault current limiters.
• Current limiting fuses.

d. Reduction of incident energy by reducing arcing time

• Bus differential protection.
• Zone selective interlocking.
• Instantaneous tripping during maintenance
• Optical sensor based arc flash protection.

e. Implementation of optical sensor based arc flash protection

• Dedicated arc flash protection relays

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Figure 5: Comparison of incident energy of different protection methods (IEEE
Std 1584, 2002)

PPE for Protection against Arc flash hazard

The threshold limit for thermal energy incident onto the skin, which will start to

cause a second degree burn is 1.2 cal/cm2 within 1 sec. This means that

thermal energies exceeding this value are expected to cause a second

degree burn to bare exposed parts of the body. In these cases, appropriate

PPE can be worn to provide a thermal barrier against burn injuries from direct

exposure to the arc, or from ignition of flammable clothing. It should be noted

that some non-flame-resistant clothing may ignite or melt at low incident

energy values of a few cal/cm2 However, the authors would again like to

stress that PPE is the last line of defense, and should be worn for protection

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 against arc flash incident energies that cannot be further reduced by

engineered means. The results from the arc flash calculations can be used to

determine the incident energy at the equipment, and, in turn, to determine

what PPE may be defined to protect personnel.

Figure 6: Distribution of thermal injuries (Schau, 2006), Borneburg, et al, 2008)

This research work shall address the following as a means of mitigating

against Arc Flash hazard (Brown, et al, 2009):

Flash protection boundary: An approach limit at a distance from exposed live parts

within which a person could receive a second-degree burn if an electric arc flash

were to occur.

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Limited Approach Boundary: An approach limit at a distance from an exposed live

part within which a shock hazard exists.

Restricted Approach Boundary: An approach limit at a distance from an exposed

live part within which there is an increased risk of shock, due to electrical arc over

combined with inadvertent movement, for personnel working in close proximity to the

live part.

Prohibited Approach Boundary: An approach limit at a distance from an exposed

live part within which work is considered the same as making contact with the live

part.

2.0 Literature Review

This section contains a brief review of literature helpful for understanding the
material presented in this work. The references in this section are relevant to
the work as a whole and several textbooks outside the field of power
engineering were particularly useful for this work.

In the context of this research work, the literature review provides a

background to the Arc flash mitigation and power system security design. It

emphasizes fundamental concepts and principles of power system dynamics

and it shows how these principles are applied.

Prior to 1982 it was assumed that electric shock was the major risk associated
with live electrical work (Graphic, 2009). In 1982, Ralph Lee published a work,
The Other Electrical Hazard, Electric Arc Blast Burns, where he describes the
thermal event associated with an electric arc and its effect on the human body.
In this work he defines the 1.2 cal/cm2 “curable burn level” that is still used
today and the calculations to determine the curable burn distance for an arc in
air. Lee’s work is considered by many people as the first research assessing
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 the hazards associated with arc flashes. In 1987 Lee published a second work
regarding arc-flash hazards, Pressures Developed from Arcs. In this work he
describes the sound and pressure effects of an arc in air. He also provides
charts to determine the pressure wave forces at distances from an arc based
on the fault level (Inshaw, et al, 2005). In 1990, the threat of an arc flash was
well-established, and Occupational Safety and Health Administration (OSHA)
updated 29 CFR-1910 Subpart S to recognize the need for arc-flash safety
(Graphic, 2009; Floyd, 2011).

Two other works have been published that look at the energies in arcing faults.
The first published in 1997, Testing Update on Protective Clothing and
Equipment for Electric Arc Exposure, uses empirical test data to determine the
incident energy at distances from a low voltage arcing fault. This was the first
work to address the directional effect of an arc in an enclosure. The second
work published in 2000, Predicting Incident Energy to Better Manage the
Electric Arc Hazard on 600-V Power Distribution Systems, provided equations
to determine incident energy based on the fault level, working distance and the
clearing time for arcs in air and in an enclosure on a 600 volt system.

Over the past ten years, papers presented at IEEE conferences have identified

the opportunity to harmonize or otherwise influence the globalization of electrical

safety-related standards. Cole et al, demonstrated improved safety and cost savings

in the design for hazardous classified locations (Cole, 1999; Roberton, 2005).

Mastrullo et al. provided a detailed comparison of U.S. and European standards

related to electrical safety for workers ( Mastrullo, 2002). Parise et al. compared

electrical design practices in Europe and the United States that impact worker

safety ( Parise, 2005). Nabours and Parise proposed the creation of an Electrical

Consulting Board to aid in advancing global h a r m o n i z a t i o n of

e l e c t r i c a l safety standards ( Nabours, 2006). Marx identified a complimentary

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 difference in European and U.S. standards ( Marx, 2008). Floyd noted that all

these papers share the common view that there are opportunities to improve

workplace safety through understanding differences in various global standards

and applying these differences in ways to enhance and augment all standards

( Floyd, 2009).

Floyd, has stated that in the comprehensive management process, the 2009

revision of NFPA 70E and the 2008 first edition of CSA Z462 include

reference to ANSI Z10-2005, Occupational Health and Safety-Management

Systems, (in NFPA 70E) and CSA Z1000-2006, Occupational Health and

Safety Management, (in CSA Z462) for a comprehensive approach for

managing exposure to hazards in the workplace. This is in recognition that

safe work practices, which are the primary content of NFPA 70E and CSA

Z462, are just a part of a comprehensive electrical safety program. IEEE 902-

1998 does not provide a detailed treatment of safe work practices as found in

NFPA 70E and CSA Z462 but provides a broader and higher level treatment

of the comprehensive elements of an electrical safety program. In further

recognition of other measures critical for optimizing electrical safety

performance, CSA Z462 includes a new annex, Annex A - Aligning

Implementation of Z462 with Occupational Health and Safety-Management

Standards. These references provide insight for aligning requirements in

different electrical safety standards to the Safety-management system

standards are based on the proven principles that are fundamental and

essential for robust safety programs and sustainable safety performance.

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 While strict implementation of requirements in individual electrical safety

standards can enable an organization to realize performance (Floyd, 2011).

The fundamentals of modeling electric power systems are covered in (Bergen,

1986), (Wood, et al, 1984), (Kundur, 1993) and (Sauer, et al, 1996). Bergen,

1986) is the most understandable. (Kundur, 1993) is the most comprehensive

and contains a good analysis of generator reactive power limits. (Wood, et al,

1984) best describes utility interconnections and economics. (Sauer, et al,

1996) has the clearest explanation of small signal stability, the effects of load

models, and Hopf bifurcations. (Golub, et al, 1996) is an excellent reference

for matrix computations. (Guckenheimer, et al, 1983) is a popular reference

for bifurcations but is not as accessible to the engineer as (Seydel, 1988).

(Seydel, 1988) is a valuable reference concerning computations and

bifurcations and is most frequently cited in power systems papers concerning

voltage collapse computations. (Garcia, et al, 1983) presents an exceptional

explanation of the path following, or continuation methods, that form the

backbone of the methods in this report.

(Peschon, et al, 1968), Van Cutsem (Cutsem, 1991), (Cutsem, 1993),

(Cutsem, 1995) & (Cutsem, et al, 1997) has forwarded an approach to steady

state stability analysis influential to this thesis. Specifically, Van Cutsem

embraces the use of loading margins that are path dependent and account for

discrete events, utilizes sensitivities and promotes the use of path following

methods as static simulation tools. Van Cutsem also provided the useful

interpretation of margin sensitivities in terms of the Lagrange multipliers of an

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 optimization problem. The new text (Cutsem, et al, 1998) contains the

aggregate of Van Cutsem’s work and a complete description of voltage

stability theory and application.

The publication of (Ibe, et al, 2004) explains the significance of Short-circuit

Current calculation in the Selection of electrical equipment. It explained that

fault current levels are compared with equipment ratings to ensure that every

device in the system is used within its fault interrupting rating. It summarized

that fault current magnitude influences the choice of electrical equipment. This

paper is well written; it has addressed all the associated issues with

equipment selection and sizing but could not emphasize the control aspect of

the Power System like the relay setting and coordination which could lead to

Power System instability if not addressed

The papers of (Ibe, et al, 2005) examined the use of Load-Flow Study as

common tools in power system analysis of the steady-state performance from

the perspective of planning, design and operation more detailed in (Nagrath,

et al, 2006). This paper describes a simple and very reliable Load-Flow study

for Power Distribution Upgrade, using asymmetrical V-bus matrix. This is a

non-linear system model and algorithm suitable for analysis of voltage angle

and real power flow referred to as the Static Load-Flow (SLF) Equation were

discussed. The recommended upgrade configuration also factors in an

estimated annual load growth of 5% in every 5 years, to prevent more severe

power interruptions or system failures in the future as demand for more power

Ph.D Research Work Page 26 of

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 grows with the present equipment ages even further. This publication

adequately addressed the issues related to Power System failure and made a

robust provision to cushion the effect of future expansion or demand. On the

other hand, the paper lacks the merit of not sufficiently addressing the

dynamic nature of Motor Starting as often experienced in Power System

network. Also Power system consumer behavior was not considered.

(Birinchi, 2004) covers Distribution System Planning Criteria, Construction

Practices of a distribution line both Overhead and Underground, Earthing

Practices, High Voltage Distribution System (HVDS), Modernization of

Distribution System, Methodology of Energy Auditing etc.

(Repo, 2004) evinces new ideas for on-line voltage stability assessment of

black-box model. The requirements and the proposed solution of all steps are

presented to provide a step-by-step procedure for the use. The thesis

describes for first time an application of linear regression models to

voltage stability margin approximation. The contributions of the thesis also

include the improvement of maximum loading point algorithm, development of

new voltage stability contingency ranking methods, and application of

data analysis methods to voltage stability studies. The main results obtained

in this thesis are an algorithm to compute the most critical voltage stability

margin, a method to create a black-box, modelling approach for on-line

voltage stability assessment and a method to approximate the most critical

voltage stability margin accurately.

Ph.D Research Work Page 27 of

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 The aim of (Nwohu, 2009) is to enhance voltage stability using Static Var

Compensator at the event of occurrence of fault in the system. In this paper,

the basic structure of an SVC operating under typical bus voltage control and

its model are described. The model is based on representing the controller as

variable impedance that changes with the firing angle of the Thyristor

Controlled Reactor (TCR), which is used to control voltage in the system.

Simulations carried out confirmed that Static Var Compensator could provide

the fast acting voltage support necessary to prevent the possibility of voltage

reduction and voltage collapse at the bus to which it is connected. Actually,

the basic control strategy is typically to keep the transmission bus voltage

within certain narrow limits defined by a controller droop and the firing angle α

limits (90° < α > 180°).

(Hodge, et al, 2009) explained the origin of DC power system constant power

instability and emphasized its highly non-linear nature. The advantages of

applying a control engineering analysis to this essentially electrical power

engineering problem have been demonstrated as the process of linearization

around a set point. The advantages of adopting this traditional analysis

technique are considerable and allow accurate assessment of the boundaries

of stability and provide useful data with respect to the dynamics of the

system’s time domain performance.

Ph.D Research Work Page 28 of

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 It has been demonstrated that by using a resistor of small value in series with

the compensating capacitor, the stability of the demonstration example can be

improved with great effect. The corresponding transient response can be

dramatically improved with respect to its form and to its time to settle.

Although this resistor is power consuming, its effect on energy-efficiency is

trivially small. This implies that this resistor does not need special cooling

arrangements to be made.

An interesting observation is that, although this arrangement introduces a

zero into the transfer function (between load voltage and the input voltage),

this zero improves the transient performance which is most agreeable. One

area the author fails to analysis is the advantage of the absence of I2t.

The International Electrotechnical Commission (IEC) has developed the IEC

61482 series of standards for clothing to protect against the thermal hazards

of an electric arc. Papers by (Schau, 2006) and (Borneburg, et al, 2008)

discuss the various test methods. However, these standards do not address

electric shock hazards, effects of noise, UV emissions, air pressure, shrapnel

or other possible projected substances such as hot oil, the consequences of

physical and mental shock or the toxic.

(Nagrath, et al, XXXX) presents an exceptional explanation of stability of an

interconnected power system as the ability of the power system to return to

normal or stable operation after having been subjected to some form of

disturbance. Conversely, instability means a condition denoting loss of

Ph.D Research Work Page 29 of

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 synchronism or falling out of step. Stability considerations have been

recognized as an essential part of power system planning for a long time.

With interconnected systems continually growing in size and extending over

vast geographical regions, it is becoming increasingly more difficult to

maintain synchronism between various parts of a power system. This book is

very good; it basically analyzed the 3 essential causes of instability in Power

System in general terms. It also explained the different types of studies

required to analyze Power System behaviour. The book reveals that stability

consideration is essential for planning because the more complex a power

system network is the more difficult it is to maintain synchronism within the

various components of the power network. However, the author should have

laid more emphasis as in (Machowski, et al, 2008) on a large range of

disturbances which may occur on a power system, because a fault on a

heavily loaded line which requires opening the line to clear the fault is usually

of greatest concern. The tripping of a loaded generator or the abrupt dropping

of a large load may also cause instability. This research would have

considered other forms of disturbances with a view to mitigating against their

occurrence.

(Machowski, et al, 1999) examines severe power system faults like short-

circuits occurring near power stations that may result in system instability. In

order to prevent asynchronous operation of the system, an automatic

generator tripping is often used but this method of transient stability

enhancement disturbs the power balance in the system and starts a long-term

Ph.D Research Work Page 30 of

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 dynamic regulation process. This paper proposes a new control algorithm

which may be used instead of the automatic generator tripping. The algorithm

identifies the transition to the asynchronous operation and acts on the turbine

governing and the excitation systems in order to stabilize the generator.

Simulation results show that stabilization can be achieved after one-two

asynchronous rotations. In this paper, the author has described excessively a

coordinated excitation and turbine control to prevent generator tripping

following severe faults. A major setback of this system is that it is difficult to

predict how many generators should be tripped in order to save the

synchronism of the remaining generators in the station. Therefore the simple

circuits with pre-determined logic have to be conservative, i.e. they usually trip

more generators than it is necessary. This is obviously a serious

disadvantage.

(Machowski, et al, 2008) gave a qualitative explanation of the underlying

physical Phenomena of power system dynamics using a simple model of the

generator, coupled with the basic physical laws of electrical engineering. This

was followed by introduction of full mathematical model of the generator.

The objective of the book (Rebennack, et al, 2010) is to investigate the

various power system stability problems, the effect of fault on the stability

condition of the system and also the post-stability condition of the system.

Another objective of stability studies according to the Author is to determine

whether the rotors of the machines being disturbed return to the original

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 constant speed operation after the disturbance. The author attempted to

examine few basic methods used to construct the Lyapunov functions for

nonlinear systems but did not give as in (Machowski, et al, 2008) sufficient

analysis of the Lyapunov functions because of its relevance in stability

studies.

Deshpade in (Deshpade, 2006), gave an overview of the need to properly

control power system for effective function. The paper identified the main

items to be controlled in a power system as the voltage, frequency and power

factor. It further explained that the transmission lines and the distribution lines

need voltage control at various stages to maintain the voltage at the last

consumers’ premises within permissible limits which will help the load

dispatcher or the control engineer to control the operation of the power

system, the remote control room and thus adjust the necessary operation of

circuit breakers, voltage, kW load distribution, kVAR distribution, frequency,

etc. In this paper, the author dwelt on the use of voltage Regulator to prevent

system voltage falling below the required level that might result to voltage

instability and eventually voltage collapse. However, the author did not

consider other methods like SVC as explained in (Nwohu, 2009), Rotor Angle

control. Basically, there are 3 essential ways that instability in a Power

System can occur: Rotor Angle, Frequency and Voltage. Each of them is

distinct in nature. However, some of the basic ideas in this book will be useful

for my work.

Ph.D Research Work Page 32 of

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 Hiskens in his paper brought out a major salient point concerning Power

System failures that are not necessarily initiated by instability but due to

inability to predict operation of protective devices. It explained that

Quantitative analysis of power system dynamics, for example, matching

simulations to disturbance measurements, requires accurate load modeling.

However load model accuracy is not so crucial for qualitative investigations,

where the aim is to assess the likelihood of a certain disturbance scenario

being stable or unstable. Though, it should be kept in mind that most power

system failures are not initiated by instability, but rather by reactionary

(unanticipated) protection operation. Accurate load modeling can be very

important in predicting such behavior. Trajectory sensitivities provide an

efficient way of ranking the relative influence of parameters. Furthermore, as

systems become more heavily stressed, sensitivity to parameter variation

increases significantly. This characteristic can be used to predict disturbance

scenarios that induce marginally stable behavior (Hiskens, 2006).

(Brown, et al, 2009; ABB, 2009) presented 5 methods for reducing arc-flash

incident energy with low voltage power circuit breaker. The optimal time–

current curve selection with maintained coordination method is useful when

downstream overcurrent protection devices will allow the short-time settings of

the circuit breaker to be lowered to a level that lowers the arc duration at the

arcing fault current level without sacrificing coordination, and when the

resulting arc-flash incident energy reduction is acceptable. The zone-selective

interlocking (ZSI) method has the potential for tremendous decreases in arc-

Ph.D Research Work Page 33 of

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 flash incident energy levels without sacrificing system selectivity. It requires

the inter-wiring between ZSI-capable trip units for implementation, i.e., no

additional equipment. Although the alternate settings method is a relatively

new method for low-voltage power circuit breakers, it does have merit so long

as operational considerations are taken. It can provide slightly lower arc-flash

incident energy levels than the ZSI method. However, during the period while

the alternate settings are in effect, system selectivity may be compromised.

This method is most useful when neither the optimal time-current curve

selection nor the ZSI methods can be used, and the com- promised system

selectivity can be tolerated for the duration of the maintenance period. It is

also useful in the case that the ZSI method produces an arc-flash incident

energy level slightly above the threshold for the next lower hazard/risk

category.

If multiple paralleled power sources are involved for a given system location

under consideration, differential relaying for that location is recommended.

The use of reduced arc-flash design circuit breakers can inherently limit the

arc-flash incident energy within the circuit breaker’s protective zone. The

amount of arc-flash reduction can be substantial. The low arc-flash circuit

breaker is most effective in lowering arc-flash incident energies when the

system parameters are within the range of its manufacturer-published incident

energy equation applicability limits, and the circuit breaker is available for the

application and ampacity required. Care must be taken to ensure that system

selectivity is retained when using this type of circuit breaker and in some

Ph.D Research Work Page 34 of

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 situations acceptable selectivity may not be possible. Good engineering

judgment favors a balanced approach, rather than the exclusive use of any of

the earlier methods. By a judicious use of these methods, systems employing

low-voltage power circuit breakers for overcurrent protection can have

reduced arc-flash incident energy levels, while at the same time retaining the

advantages of using circuit breakers.

This research work is builds upon earlier work conducted by Raph Lee (Lee,

1982), NFPA70E (NFPA 70E, 2012), IEEE 1584 (IEEE Std 1584, 2002),

IEEE C37.20.2-1999 (IEEE C37.20.2, 1999).

A total of 82 books and journals have been reviewed, the table below shows

specimen of consulted research material that are key to this research work.

Title of Date of
Ref Name of Title of Problem Strength of Weakness of
Journals, Publication Methodology
No. Authors Paper Solved method method
Vol/PP
The Effects 1956 Perception The paper Created The paper
of Electric tests presented knowledge of the could not
Shock on possible possible effects of establish
Man quantitative electric current on experimentally
effects of' man as the on man
2 Charles F. electric starting point at current likely
Dalziel currents on which to to produce
man incorporate safety instantaneous
into the design of death
electrical
equipment.

The Other IEEE Trans. Theoretical The research develop a The work was
May/June methods for explained the relationship limited to low
Electrical Industrial
1982. evaluating relationship between heat voltage
Hazard: Applications,
incident between heat transfer and applications.
Electric Arc Vol. 1A-18, energy of an transfer from distance with its
4 Blast Burns No. 3, p246 arc in open hotter to effects on human
air cooler objects skin tissue
and the
Ralph Lee importance of
the distance
between them.
Richard L. Predicting IEEE, 1998 This research The testing led this testing also This proved
Doughty, Dr. Incident Paper No. detailed a to algorithms showed an important
Thomas E. Energy to PCIC-96- testing for predicting increase in because most
5
Neal, H Landis Better 36, 1998 program incident incident energy arcs occur
Floyd Manage completed to energy based when the source when a
The measure on available is in an enclosure person is

Ph.D Research Work Page 35 of

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 Electric Arc incident fault current with an open door standing in
Hazard on energy from and the versus a source in front of an
600 V 6-cycle arcs distance from open air, such as open electrical
Power on 600 volt the source an overhead enclosure and
Distribution power conductor the arc is
Systems systems. confined in the
panel-board or
switchgear
IEEE Guide IEEE Arc-Flash empirical method to This method
for Arc Standard 2002 Hazard method calculate the does not take
Flash 1584-2002 Calculations incident energy into account
Hazard from the arc due energy
Calculations to heat, which is associated
responsible for with pressure-
the most common wave effects,
IEEE 1584 effect of an arc- such as flying
6 flash event: debris. It is
Burns. applicable
only over a
given range of
system
voltages,
frequencies,
and fault
currents

Title of Date of
Ref Name of Problem Strength of Weakness of
Title of Paper Journals, Publicatio Methodology
No. Authors Solved method method
Vol/PP n
“Occupation March Fire This research The research was There is a
al Injuries 2015, Pp Protection analyzed the able established need for more
from 13 Research workplace that electrical empirical
Electrical Foundation electrical injuries do not incident data
Shock and injury take place in a on the actual
Arc Flash experience in vacuum. hazards that
Richard B. Events, the United Violations of basic may be
Campbell, Final States for a electrical safety experienced
David A. Report” period of 20 requirements when
7
Dini years and figure prominently equipment
concluded that in the federal faults or
there is a OSHA annual top adverse
general ten list of the most electrical
decline as frequently cited events occur
recorded workplace health
annually. and safety
violations

Reducing the IEEE June, Analytical Methods to Use of None

Flash Hazard," Industry 2007 protect appropriate
IEEE Industry Application workers from electrical design
11 Timothy B. Applications Magazine the changes to
Dugan Magazine devastating implement means
effects of arc of reducing
flash incident energy.
12 Practical National 2003 Presented This guide
Solution Guide Technology several presents the basic
C. Davis et to Arc Flash Transfer methods for steps for
al: Hazards. (NTT), calculating Arc performing an arc
ESA, Inc., p flash with flash hazard
3-4. assessment of assessment using
arc flash power analysis
hazards software

Inshaw C. Arc Flash Hazard IEEE 58TH 2005 Mathematical This paper It identified the This paper did
and Wilson Analysis and Annual modelling described the easiest and most not lay
R. Mitigation” in Conference process of arc cost effective emphasis on
15 58th Annual flash hazard means of limiting increased
Conference for analysis, arc flash hazards system
Protective Relay including the by limiting the reliability
Engineers] calculation of arcing time using

Ph.D Research Work Page 36 of

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 incident a dedicated arc-
energy flash detection
relay.
Pressures IEEE July/August levels in arc This paper The use of charts The
Developed by Transactions 1987 flash faults describes the to determine the interaction
Arcs on Industry and selection sound and pressure wave between
Applications, of appropriate pressure forces at various human factors
Vol. IA-23, effects of an distances based and
Ralph Lee No. 4. page arc in air. on the fault duties equipment
16 760-764 at the location malfunction is
consistently
noted during
accident
investigations
were no dealt
with

Ph.D Research Work Page 37 of

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 Title of Date of
Ref Name of Methodolog Strength of Weakness of
Title of Paper Journals, Publicatio Problem Solved
No. Authors y method method
Vol/PP n
Staged Tests IEEE March/Apri experimental The intent is to The test results The
Increase Awareness Transaction l 2000 results of improve included in the interaction
of Arc-Flash s on staged tests understanding of paper broaden between
Hazards in Electrical Industry simulating how people are the base of arc human factors
Equipment. Applications the exposed to flash research and
, Vol. 36, participation electrical and underscore equipment
20 Ray A. No. 2, page of workers in hazards in the malfunction is
659-667 the test industrial unpredictable consistently
Jones, et al
scenario settings so that nature of arc noted during
prevention flash accident
strategies may investigations
be enhanced were no dealt
with

53 Martin Infrared Windows IRISS, inc 2008 Thermograp This work Infrared IR windows
Robinson and Arc Ratings – hic introduces Arc inspections of are not
& Tim Dispelling the inspection rated switchgear electrical intended to
Rohrer. myth of “Arc- and MCCs which systems are protect a user
Resistant IR enlist a variety of beneficial to from an arc
Windows” safety reduce the flash - they
mechanisms number of are intended
such as costly and to eliminate
additional catastrophic additional
barriers and equipment triggers of an
pressure relief failures and arc flash
mechanisms. unscheduled during an
These safety plant inspection and
features redirect shutdowns. replace a
the forces and high-risk
heat of an arc activity with a
flash away from risk
the panel doors reduction/elimi
and up through a nation
series of strategy
plenums that during
systematically inspection.
reduce the
forces of the
blast and
minimize any
damage that
might have
otherwise
occurred had the
blast escaped
the confines of
the system.

Ph.D Research Work Page 38 of

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 Title of Date of
Ref Name of Strength of Weakness of
Title of Paper Journals, Publicati Methodology Problem Solved
No. Authors method method
Vol/PP on
54 Robert A. Application of Arc- 1997 This paper In conventional
Patten, E. Resistant Metal- discusses the metal-clad
John Clad Switchgear trends towards switchgear, the
Saleeby in Power arc-resistant result is
Distribution switchgear and catastrophic to
Centers describes the nearby
ABB solution for personnel and
integrating arc- equipment. The
resistant extensive
switchgear into damage also
Power means high
Distribution repair costs
Centers and down time.
60 ABB Inc. Low Voltage www.abb.u Novemb This document Fault area is This system
888-385- Circuit Breakers s/l er, 2009 sums up the precisely unnecessary
1221. Arc flash hazards owvoltage recommendation identified by the increase the
www.abb. s of the US use of Zone time delay
com/lowvo standards for all selectivity. This closer to the
ltage personnel selectivity supply source
working on live allows faster
electrical tripping times
equipment. than time-
current
selective
coordination

Ph.D Research Work Page 39 of

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2.1 Theoretical Framework

One of the most important and essential elements of an arc flash hazard

analysis is the estimation of the incident energy. These calculations help

predict the amount of energy available during an arc flash event. Incident

energy is typically expressed in (Joules) J/cm2 or (calories) cal/cm2. The

calculations detailed by NFPA 70E-2004 and IEEE 1584-2002 are used to

establish the flash protection boundary, i.e. the distance from an arc source

that would cause the onset of a second degree burn. The energy required to

produce a curable, second degree burn on unprotected skin has been

established as 5.0 J/cm2 (or 1.2 cal/cm2).

According to Ralph Lee (Lee, 1982), arc flash boundary is a function of

bolted fault MVA. This assumes the maximum possible arc power as half the

total available fault MVA or bolted fault MVA.

𝐷𝐵 = √2.65 ∗ √3 ∗ 𝑉 ∗ 𝐼𝑏𝑓 ∗ 𝑡 1

Where,
DB = distance of the boundary from the arcing point (feet)
V = system voltage L-L (kV)
Ibf = bolted fault current (kA).
t = arcing time (seconds)

This formula is applicable when definite time trip function is used to interrupt

the fault. A definite time trip function is a fixed time delay which is

independent of the fault current passing through the protective device.

Instantaneous trips are also approximately fixed time in most devices. If the

Ph.D Research Work Page 40 of

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 trip time is independent of the fault current, then making the assumption that

the arc current may have a value that will yield the maximum arc power is

justified. However, this formula needs to be modified if the trip time is a

function of the fault current. Inverse type relays, fuses, thermal trip units

and solid state trip units with I2T time delays have current dependent trip

time. Assessment for inverse time functions can be approached using the

same circuit assumptions with which the above equation (2) was derived.

Figure 6 : Equivalent circuit diagram with arc components

Fig 6 is the Thevenin equivalent circuit for the arc fault is shown.

W h e r e , V The system voltage, V, is at the point of fault, while Ra is

the equivalent arc resistance, Xs and Rs are components of the

Thevenin impedance Zs, and Iarc is the arc current. When the arc

resistance is zero (a hypothetical case), the arc current is equal to the

bolted fault current. No power is dissipated through the arc. As the

arc resistance increases, the arc current decreases. The arc power

reaches a maximum when the arc current is approximately 0.7 per unit

of the bolted fault current. This holds true only if the X/R ratio of the

system is very high (Rs is negligible). If the X/R ratio is low, then the

maximum power transfer occurs when arc current ratio (Iarc/IBF) is less

Ph.D Research Work Page 41 of

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 than 0.7, and the maximum arc power is less than 0.5 times the bolted

fault MVA. A plot of arc power as a function of arc current is shown in

Figure 7. The arc power and arc current have been normalized in this

plot.

Figure 7 : Plot of arc power as function of arc current.

Arc current is expressed in per unit of the bolted fault current and the arc

power is expressed in per unit of the maximum arc power.

Determine the Arc Flash Boundary

The flash boundary is determined as the distance from the arc fault at which the

incident energy is equal to 1.2 cal/cm2.

Empirical Method (1-15 kV):

1
𝑡 610𝑥 𝑋
𝐷𝐵 = [𝐶𝑓 𝐸𝑛 (0.2) ( )] 2
𝐸𝐵

Lee Method (15+ kV):

Ph.D Research Work Page 42 of

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 𝑡
𝐷𝐵 = √5.12𝑥105 𝑉𝐼𝑏𝑓 (𝐸 )
𝐵
3

Where:
DB = the distance (mm) of the Flash Protection Boundary from the arcing
point
Cf = a calculation factor
= 1.0 for voltages above 1 kV
= 1.5 for voltages at or below 1 kV
En = incident energy normalized
EB = incident energy in J/cm2 at the distance of the Flash Protection
Boundary
t = time (seconds)
X = the distance exponent
Ibf = bolted three phase available short-circuit current
V = system voltage in kV

3.0 RESEARCH METHODOLOGY

To fulfill the objective of this work, the following methods for modelling and

simulation of arc flash hazard will be examined and adopted.

• The application of the equations and tables used in NFPA 70E-2004. This

method uses a hazard category classification table, that is found in NFPA

70E

• IEEE 1584 equations for small radial distribution systems.

• Commercial integrated software (ETAP)

• Spreadsheet calculator

4.0 EXPECTED RESULTS OUTCOME

▪ To design an Arc Flash Resistance that will prevent worker injury or death
Ph.D Research Work Page 43 of
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 ▪ To Minimize equipment damage and system down time

▪ To develop guideline for arc mitigation for the Nigeria Electricity Supply

Industry (NESI

5.0 CONCLUSION

In summary, reduction of arc-flash hazards in equipment is an essential

requirement for electrical equipment. The goal is to minimize personnel

exposure to the arc flash incident energy by applying arc flash resistance

solutions into a modern switchgear and motor control center configuration,

minimizing arc flash energy levels. It is generally accepted that a second-

degree burn results from exposure of incident energy of 1.2 Cal/cm2 defined

as hazard category 0. The duration of the arc has a significant effect on

incident energy released and incident energy exposure to personnel. The

bottom line is to provide a system that reduces the likelihood of an arc-flash

hazard to occur. This is the main goal of this work.

Ph.D Research Work Page 44 of

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