NECA Services - WHS
EASY GUIDE
TO ARC FLASH
ANALYSIS
ELECTRICAL SAFETY
PROGRAM
When working, testing or fault finding
on energised electrical equipment,
a fault current of up to 20 times the
rated current of the supply transformer
can flow for short duration during fault
conditions.
Arcs can have the energy to cause
an explosion and/or melt metallic
switchboard cubicles and equipment.
Arcs may cause severe burns to the skin
and flash burns to the face and eyes.
Inhaled hot gases and molten particles
can cause serious internal burns to the
throat and lungs. Injury can also occur
through the impact from flying debris
and dislodged components. Circuit
protection devices may not operate in
such circumstances.
WHS Regulation 158 and 161
both states that if electrical work is to
be carried out on energised electrical
equipment an electrician must ensure
that risk assessment is carried out by
a competent person who has tools,
testing equipment and PPE that are
suitable for the work and have been
properly tested and are maintained.
To clarify what work on energised
electrical equipment means, it is any
task that includes the following:
• Isolating
• Switching
• Removing fuses or links
• Isolation verification (testing for
dead)
• Testing
• Fault finding
• “Live” work
This is work that electricians do every
day. Having a “No Live Work” Policy
cannot rule out all the circumstances
when electrical hazards exist in the
electricians environment. If you employ
electricians, you cannot say that they
never work live.
A risk assessment involves considering
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what could happen if someone is
exposed to a hazard and the likelihood
of it happening. Risks associated
with electrical work may arise from
the properties of electricity. Electricity
is particularly hazardous because
electrical currents are not visible and do
not have any smell or sound. The risk
assessment should also consider how
and where the electrical work is carried
out. Electrical work may be carried out
in difficult conditions, including in wet
weather conditions, confined spaces
and in atmospheres that present a
risk to health and safety from fire or
explosion.
It is becoming more and more
common for larger transformers to be
used to power domestic installations.
This has created a situation where
the short circuit currents are much
higher than they used to be. A typical
transformer to power a street of
houses may have been 100kVA. Now
it is not uncommon to see 300kVA
or even 500kVA transformers. This
can result in short circuit currents of
20kA and above. To make matters
worse, a number of well known
manufacturers sell cheap low quality
circuit breakers that have a rating of
only 3kA. Electricians are continuing to
use these without understanding the full
ramifications of their decision.
The proliferation of solar panels,
energy storage and uninterrupted
power supplies (UPS) used in industrial,
agricultural, commercial building and
even the residential sector increases the
risk of exposure to safety hazards that
are inherently associated to nonlinear
power sources. With more complicated
systems being installed increasing the
likelihood and severity of an electrical
arc flash the need for a systematic
approach to managing occupational
health and safety in the electricity
industry is needed more than ever.
All electrical contractors and
businesses should have in place an
Electrical Safety Program which includes
training, procedures, electrical risk
assessments, appropriate rated PPE
and the right tools and equipment to
do the task. Clothing should be flame
resistant. Do not settle for minimal
performance, make sure you do your
homework and have options that meet
the needs of work. Components of an
Electrical Safety Program include:
• Defining safe work practices and
use requirements for all people who
work with electrically energized
equipment as part of their normal
job / research duties.
• Establishing training requirements
for "qualifying" and "authorising"
persons who work on or near
energized electrical circuits and
components, and establishing
"qualification" requirements for
electrical contractors.
• Establishing a process for
evaluating and calculating the
hazards of every potentially
energized electrical work task and
for determining appropriate hazard
controls.
• Establishing a formal process for
controlling energized electrical
work through an assessment and
documented "energized work"
process.
• Chartering an "Electrical Safety
Committee" to oversee work
practices and procedures.
• Consulting with electrical safety
experts at NECA, Safety Regulators
and Network providers.
A good risk assessment process will
include a calculation of incident energy
which is used for the selection of PPE
and controls. Most electricians are
daunted by the prospect of an Arc Flash
calculation and normally bypass the
important risk assessment procedure
because they have never been trained
on how to undertake it. Sure, to get
super accurate results you probably
need to have an engineering degree and
some complex software. However, a
basic calculation to determine a safety
control is much easier to complete.
Calculating incident energy also has
other benefits, it helps identify one of
the most common design faults found
in electrical circuits by distinguishing
incorrectly sized circuit breaker fault
current ratings (commonly called
the kA rating). You can also use this
calculation to know when to implement
other traditional controls such as safety
observers, low voltage rescue, insulation
mats etc.
Once it is determined that PPE is
required, choosing the PPE that is
best for the situation seems like a
daunting task. Working around electrical
equipment ranging from 100-amp
residential panels to 4,000- amp
commercial and industrial switchgear
offers a wide range of available fault
current that could lead to injury in the
event of an arc flash or electric shock.
Although this type of basic calculation
is useful as a guide to select PPE where
there is no other information available,
it is clear that assumptions will have
to be made and may not necessarily
be applicable to the systems you may
be analysing. As such, they will often
lead to over classification of protective
gear for work on a specific piece of
equipment. However, it is of even more
concern that there is a potential for
under classification of the protective
gear recommended for work on a
specific piece of equipment. Therefore
this advice should be considered as
guidance only and the table below
should not be blindly accepted.
1. Time of Day
The time of day is important when
undertaking this risk assessment, you
should pick a time when the property is
at full load and solar array systems are
producing the most wattage.
2. Site Walkabout
Because conditions may have
changed since the original installation,
it is critical that the existing conditions
be field verified to ensure that the
arc flash analysis is performed using
accurate breaker settings and field
conditions. Start by walking around the
site identifying locations of transformers
or substations and their proximity to the
equipment to be worked on. Also, look
for solar array systems, inverters, battery
backup/storage and UPS equipment.
Include power floor plans showing
locations of electrical equipment, and
single-line diagrams indicating the
overcurrent protective devices and cable
sizes for all relevant areas.
3. Make an Assumption about
Fault Levels
prospective fault current requires
the testing of energized circuits, it is
important that sufficient PPE be in
use before this test is undertaken,
but without the calculated value of
incident energy, you will need to make
an assumption. To err on the side of
caution you should over classify your
level of protective gear for the initial test.
Once the calculation is complete, you
will be able to predict the level protective
gear actually needed.
To make this assumption use the kA
rating of the main circuit breaker in the
switchboard that you are working. The
value of the kA rating determines how
much current the circuit breaker can
withstand under fault conditions. The
circuit breaker only has to withstand
this for a brief period, usually the time it
takes for the circuit breaker to trip. For
example, a value of 6kA means that
the circuit breaker can withstand 6,000
amps of current during the brief time it
takes to trip.
If this is still not available, you can
assume 12kA for single domestic
dwellings or 40kA for all other
commercial, industrial or residential
units.
4. Select your PPE
Line up your kA rating with the most
appropriate row in the table below and
utilise the recommended PPE.
Continue next page 
Because the process of calculating
Prospective Short Minimum Arc
Circuit Current
Rating Protection
(KA) Range
Range
Under Garments
Base Garments
0-10.5
•wool or cotton
•ATPV of min
5.6 Cal/cm2
•Safety Glasses
•ATPV of min
5.6 Cal/cm2
•Face Shield with
chin cup of ATPV
min 10 Cal/cm2
•Fire resistant
gloves
•Rubber Mat
•ISSC 14 Electrical
First Aid kit
•Face shield with
chin cup of ATPV
min 10 Cal/cm2
•Fire resistant
gloves
•Safety Observer
•LV Rescue Kit
•ISSC 14 Electrical
First Aid kit
•Rubber Mat
•Hood ATPV min
20 Cal/cm2
•Insulated gloves
with leather or fire
resistant outers
Gloves
•Safety Observer
•LV Rescue Kit
•ISSC 14 Electrical
First Aid Kit
•Rubber Mat
10.5-20.45
20.45 - 43.3
0-3 Cal/cm2
3-5 Cal/cm2
5-10 Cal/cm2
•wool or cotton
•wool or cotton
• ATPV of min
5.6 Cal/cm2
Outer Garments
• Overall ATPV
of min 8 Cal/
cm2
• Switching suit
ATPV of min
20 Cal/cm2
43.3 - 85.3
10-20 Cal/cm2
• ATPV of min
•wool or cotton
5.6 Cal/cm2
85.3Ka+
20+ Cal/cm2
Hold Point
Expert Arc Flash and shock hazard analysis required
Face & Hand
Protection
Other
March/April 2016 Issue 1
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NECA Services - WHS
Continued from page 63
5. Test for Prospective Short
Circuit Current
Perform a short-circuit analysis at the
most upstream point of the exposed
equipment being worked on or the
switchboard— the prospective short
circuit (PSC) or fault is the current that
would flow in the circuit if no circuit
protection operated and a complete
short circuit occurred. The supply
voltage and the impedance of the path
taken by the fault current determine the
value of this fault current. Measurement
of PSC can be used to check that
protective devices within the system will
operate within safety limits and as per
the safe design of the installation. The
kA rating of a circuit breaker is a very
important safety aspect to consider
when designing a circuit. Without it,
there is a good chance that a serious
accident will occur. PSC is also used to
determine Incident Energy (IE), which
is the purpose of this test. Ensure you
follow the instructions of your testing
device to obtain the PSC.
6. Calculate Incident Energy
IE of an arc flash is dependent upon
the length of the flash, the available
PSC, and inversely (and exponentially)
related to one's distance from the origin
of the flash.
NENS 09 proposes the following
formulas to calculate the incident energy
likely to be developed 450mm directly in
front of the conductors, where:
IE: Incident energy (cal/cm2)
t: Fault duration (sec) – this is typically
0.1 for molded circuit breakers, 0.4
A PROSPECTIVE SHORT CIRCUIT (PSC) OR FAULT
NECA INCIDENT ENERGY CALCULATOR
Prospective Three Phase Bolted Fault Current (lrms) in amps
Insert prospective three phase symmetrical bolted fault current in this box.
Note - Arcing current is assumed to be 30% of the bolted short-circuit fault current.
Fault Clearance Time (t) in seconds
Refer to upstream protection device time current-curves
Default Fault Clearance Time = 0.1 seconds
Distance (r) in metres
5400
0.1
The distance of the individual from the arc source.
Default Fault Clearance Time = 0.45m
0.45
Calculated Incident Energy (IE) in calories/cm2 for COPPER
0.74
Calculated Incident Energy (IE) in calories/cm2 for
ALUMINIUM
0.85
Minimum Arc Flash Protection value
2.05
WHS Regulation 158 states that if electrical work is to be carried out on energised electrical equipment a person
conducting a business or undertaking must ensure before the work commences that:
• a risk assessment is conducted by a competent person in relation to the proposed work
• and recorded
• the area where the electrical work is to be carried out is clear of obstructions so as to allow for easy access and
exit
• the point at which the electrical equipment can be disconnected or isolated from its electricity supply is:
• clearly marked or labelled, and
• cleared of obstructions so as to allow for easy
access and exit by the worker who is to carry
out the electrical work or any other competent
person, and
•capable of being operated quickly
• the person authorises the electrical work after consulting with the person with management
• or control of the workplace.
Requirements relating to the point of supply under the third dot point above do not apply if the work is to be carried out
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March/April 2016 Issue 1
for fuse protected equipment and
0.5 seconds for HV – check the fuse
clearing time for the circuit involved.
r: Distance from arc (metres) this is
typically 450mm
Irms: three phase fault current
(amps).
The formulas are:
• Copper electrodes: IE = 3.8 x 10-4
x t x Irms1.12/r2
• Aluminium electrodes: IE = 4.4 x
10-4 x t x Irms1.12/r2
IF this seems to hard, you can
complete this calculation using the
NECA incident energy calculator found
on the NECA NSW website
www.neca.asn.au/nsw.
7. Add a Safety Factor
due to the time of day and connected
load, it is important to add an additional
safety factor to your target score.
This safety value will also compensate
any changes to the field conditions
as maintenance and upgrades occur
during the year. By adding 1.2 Cal/
cm2 to the calculated value should
be sufficient to compensate for any
variation for your target safety/PPE
value. If you are using the NECA
incident calculator this will automatically
be calculated. This new value is known
as the ‘Minimum Arc Rating Protection’
value. PPE protection must be greater
than this value.
8. Repeat Step 4 to Select Your
PPE
Repeat step 4 but now use the
appropriate Cal/cm2 column instead of
Because variation in the PSC value
the kA column
9. Document your findings
Assemble a report including floor
plans, calculation, risk assessment and
provide to client and keep on file for
length of job or 5 years.
10. Label the board
Label the board/equipment that you
were working in. Labeling will help the
next time you work from that board or
help other electricians with their PPE
choices. You can download a ready to
print label from the NECA NSW website.
Owen Leslie
Work Health & Safety Manager
NECA NSW & ACT
Ref: 1601-WHS-62/65
Sample ARC Flash & Shock Hazard Appropriate PPE Required label - ready to download FREE
from the NECA NSW website www.neca.asn.au/nsw
ARC FLASH & SHOCK HAZARD
APPROPRIATE PPE REQUIRED
DANGER
Minimum Arc Rating
Protection (cal/cm2)
Tested by:
Prospective
Short Circuit
current (KA)
Range
Minimum
Arc Rating
Protection
Range
0-10.5
10.5-20.45
Under
Garments
Base
Garments
Outer
Garments
0-3 Cal/cm2
• wool or cotton
• ATPV of min
5.6 Cal/cm2
• Safety
Glasses
3-5 Cal/cm2
• wool or cotton
• ATPV of min
5.6 Cal/cm2
• Face Shield
with chin cup
of ATPV min
10 Cal/cm2
• Fire resistant
gloves
• wool or cotton
• ATPV of
min 5.6 Cal/
cm2
• Overall
ATPV of min
8 Cal/cm2
• Face shield
with chin cup
of ATPV min
10 Cal/cm2
• Fire resistant
gloves
• Safety
Observer
• LV Rescue
Kit
• ISSC 14
Electrical
First Aid kit
• Rubber Mat
• ATPV of
min 5.6 Cal/
cm2
• Switching
suit ATPV of
min 20 Cal/
cm2
• Hood ATPV
min 20 Cal/
cm2
• Insulated
gloves with
leather or
fire resistant
outers Gloves
• Safety
Observer
• LV Rescue
Kit
• ISSC 14
Electrical
First Aid Kit
• Rubber Mat
Licence:
Test date:
Test due:
MINIMUM SAFETY REQUIREMENTS & PPE
Cotton or wool underwear
Safety observer
Base garments ATPV min 5.6 Cal/cm2
long sleeve shirt and trousers
Face shield with chin cup of ATPV
min 10 Cal/cm2
Overalls ATPV of min 8 Cal/cm2
ISSC 14 electrical first aid kit
Switching suit ATPV of min 20 Cal/cm2
Arc rated gloves
Safety glasses
Insulation gloves
LV rescue kit
Rubber mat
Reference:
NECA NSW Arc Flash
Protection Safe Working
Procedure
Incident energy calculator
available on the NECA website
T: 1300 361 099
F: 02 9744 1830
W: www.neca.asn.au
20.45 - 43.3
5-10 Cal/cm2
43.3 - 85.3
10-20 Cal/
cm2
• wool or cotton
85.3Ka+
20+ Cal/cm2
Hold Point
Expert Arc Flash and shock hazard analysis required
Face & Hand
Protection
Other
• Rubber Mat
• ISSC 14
Electrical
First Aid kit
on the supply side of the main switch on the main switchboard for the equipment and the point at which the equipment
can be disconnected from its electricity supply is not reasonably accessible from the work location.
WHS Regulation 161 requires a person conducting a business or undertaking must ensure that electrical work carried
out on energised electrical equipment is carried out:
• by a competent person who has tools, testing equipment and PPE that are suitable for the work, have been
properly tested and are maintained in good working order
• in accordance with a safe work method statement prepared for the work, and
• subject to the exception explained below—with a safety observer present who is competent:
• to implement the control measures in an emergency
• to rescue the worker who is carrying out the work if necessary, and
• has been assessed in the previous 12 months as competent to rescue and resuscitate a person.
A safety observer is not required if the work consists only of testing and the risk assessment shows there is no
serious risk associated with the proposed work.
The person must ensure, so far as is reasonably practicable, that the person who carries out the electrical work uses
the tools, testing equipment and PPE properly.
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