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IEEE 1584 2.0 Changes Highlights

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More analytical complexity,

more effort,

more decisions,

more inputs required �

more opportunities for mistakes…

IEEE 1584 2.0 model is more complex than the 2002 model

30/03/2019 Slide 2

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Current Model (2002):

Contains approximately 3 pages of math

New Model:

• IEEE 1584 2.0 contains 17 pages of formulas, coefficients

and exponents.

• Also, more variables for a more representative model of

actual conditions… but more representative does not

mean “exact”

IEEE 1584 2.0 model is more complex than the 2002 model

30/03/2019 Slide 3

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IEEE-2002 vs. IEEE 1584 2.0

30/03/2019 Slide 4

Current (2002) calculation variables:

• Gap (G) (equipment type driven)

• Working distance (D)

• Operating voltage (Voc)

• Available short circuit current (Ibf)

• Grounding (yes/no) (not new model)

• Box (yes/no)

What is the difference?

New model (2019) will add:

• Electrode orientation

• Electrode environment (barriers?)

• Box size considerations

• More variable gap considerations

• Results may vary significantly

• Arcing Current (Ia)

• Incident Energy (Ei)

• Approach Boundary

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• The orientation and arrangement of the electrodes used in the testing evolved.

• Electrodes placed in open-air (“OA”) or enclosed (“B”) (open front).

• Electrodes were also oriented vertically (“V”) or horizontally (“H”).

• Open space & barrier-terminated (“B”) electrode configurations also used.

Electrode configurations defined and listed in the model:

VCB: Vertical electrodes inside a metal “box” enclosure.

VCBB: Vertical electrodes terminated in a “barrier,” inside a metal “box”.

HCB: Horizontal electrodes inside a metal “box”.

VOA: Vertical electrodes in open air.

HOA: Horizontal electrodes in open air.

Electrode configuration is a big change!

30/03/2019 Slide 5

From 2 event modes to 5

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Horizontal electrodes aim plasma at

the worker!

Common sense � more dangerous…

“plasma rail”

aiming at worker!

The data confirms it!

Biggest difference is electrode direction

30/03/2019 Slide 6

Horizontal versus vertical makes a big difference.

Heat & plasma bounce around the

box & get pushed out via radiation

& pressure

Lorentz force pushes arc (plasma)

away from “end” of electrodes

Heat & plasma focused on worker

OLD MODEL

Additional in NEW

MODEL

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Vertical electrodes inside metal

box enclosure.

Illustration of VCB

30/03/2019 Slide 7

Worker is mostly parallel to the

direct plasma stream

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Vertical electrodes terminated in a barrier inside a metal box

Reduced space “under” the circuit breaker

Illustration of VCBB

30/03/2019 Slide 8

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Horizontal electrodes inside a metal box

Best examples are probably the runbacks on any switchgear

Illustration of HCB

30/03/2019 Slide 9

Worker is mostly perpendicular to

the direct plasma stream

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Vertical electrodes in open air

Frequently an outdoor issue

Illustration of VOA

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The electrodes are vertical.. But

where is the worker?

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Horizontal electrodes in open air

• This equipment shows a “triangular” pattern

• Which produces more energy

Illustration of HOA

30/03/2019 Slide 11

• Dry data in software may not be enough…

need to assess situation for worker’s risk &

know it’s covered

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Two methods

• Model for 600 ≤ Voc ≤ 15000 Volts

• Model for 208 ≤ Voc < 600 Volts

But no discontinuity in arcing current or energy function like old model at 1000V

Two-step process

1. Intermediate values of average arc current, incident energy and arc-flash boundary are

interpolated, or extrapolated to determine final values

2. Correction factors for enclosure (box) size and arc current variation are applied to adjust

results.

Similar to 2002 regarding current variation, box size variation is a new twist!

2 step process continuous over voltage range

30/03/2019 Slide 12

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Three equations, one at each of the three Voc (600, 2700 & 14300 V)

must be solved with 10 different coefficients each

600 V - 14.3 kV, Intermediate Arcing Current Value

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600 V - 14.3 kV, Intermediate Arcing Current Value

30/03/2019 Slide 14

Example of coefficient tables (1 of 6)

k1 k2 k3 k4 k5 k6 k7 k8 k9 k10

600V -0.04287 1.035 -0.083 0 0 -4.78E-09 1.96E-06 -0.000229 0.003141 1.092

2700V 0.0065 1.001 -0.024 -1.56E-12 4.56E-10 -4.19E-08 8.35E-07 5.48E-05 -0.003191 0.9729

14300V 0.005795 1.015 -0.011 -1.56E-12 4.56E-10 -4.19E-08 8.35E-07 5.48E-05 -0.003191 0.9729

600V -0.017432 0.98 -0.05 0 0 -5.77E-09 2.52E-06 -0.00034 0.01187 1.013

2700V 0.002823 0.995 -0.0125 0 -9.20E-11 2.90E-08 -3.26E-06 0.0001569 -0.004003 0.9825

14300V 0.014827 1.01 -0.01 0 -9.20E-11 2.90E-08 -3.26E-06 0.0001569 -0.004003 0.9825

600V 0.054922 0.988 -0.11 0 0 -5.38E-09 2.32E-06 -0.000302 0.0091 0.9725

2700V 0.001011 1.003 -0.0249 0 0 4.86E-10 -1.81E-07 -9.13E-06 -0.0007 0.9881

14300V 0.008693 0.999 -0.02 0 -5.04E-11 2.23E-08 -3.05E-06 0.000116 -0.001145 0.9839

600V 0.043785 1.04 -0.18 0 0 -4.78E-09 1.96E-06 -0.000229 0.003141 1.092

2700V -0.02395 1.006 -0.0188 -1.56E-12 4.56E-10 -4.19E-08 8.35E-07 5.48E-05 -0.003191 0.9729

14300V 0.005371 1.0102 -0.029 -1.56E-12 4.56E-10 -4.19E-08 8.35E-07 5.48E-05 -0.003191 0.9729

600V 0.111147 1.008 -0.24 0 0 -3.90E-09 1.64E-06 -0.000197 0.002615 1.1

2700V 0.000435 1.006 -0.038 0 0 7.86E-10 -1.91E-07 -9.13E-06 -0.0007 0.9981

14300V 0.000904 0.999 -0.02 0 0 7.86E-10 -1.91E-07 -9.13E-06 -0.0007 0.9981

VOA

Table 1, Coefficients Iavg, V 2.6.2

HOA

VCB

VCBB

HCB

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Values calculated at 3 voltages, 600,

2700 & 14300V… then interpolated

to actual Voc

Intermediate values of energy

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Box Correction Factor

30/03/2019 Slide 16

Logic rules select formulas for CF from normalized data… not intuitive

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• Single phase method: use single phase current & 3 phase formulas!

TOO conservative? Can probably divide energy by 3.

• DC arc research starting now!

Single phase and DC

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Working distance, important

for energy, no effect on Iarc

36” for hot stick work

18” for manual work

24” for deep cubicles

Working distance

30/03/2019 Slide 18

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Same:

Ibf (rms, 50/60Hz):

208–600V: 500A-106 kA

601V– 15kV: 200A- 65 kA

Sustainable arcs are possible but are less likely in 240V 3-phase systems with Ibf < 2kA

Different:

Conductor Gap

208– 600V: 6.4mm (0.25in) - 76mm (3in)

601V – 15kV: 19mm (0.75in) - 254mm (10in)

Different:

Working distances:

minimum 305mm (12”),

LV tests to 47”, MV to 36”

Different:

Fault Clearing Time:

2 S. rule still in but its only guidance!

Model Range

30/03/2019 Slide 19

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If the total protective device clearing time is longer than 2 seconds; consider how long a

person is likely to remain in the location of the arc-flash. It is likely that a person exposed to

an arc flash will move away quickly if it is physically possible, and two seconds usually is a

reasonable assumption for the arc duration to determine the incident energy. However, this

also depends on the specific task. A worker in a bucket truck, or inside an equipment

enclosure, could need more time to move away. Use engineering judgement when applying

any maximum arc duration time for incident energy exposure calculations, since there may

be circumstances where a person’s egress may be blocked.

Also in 70E-2018, D.2.4 (2) ! Part of the risk assessment portion of the analysis

2 second rule

30/03/2019 Slide 20

In 6.9.1 General

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The more absolute the more secure

The more automatic the more secure

The less it depends on actions by the person becoming safer, the better

Humans make mistakes!

Do not forget - Hierarchy of Hazard Controls

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1. Elimination of the hazard

2. Substitution of less hazardous

equipment or materials

3. Engineering control to reduce

exposure or severity

4. Warnings, signs, and other

communications

5. Administrative control, including

safe work practices

6. Personal Protective equipment

Secured & verified de-energization

Smaller transformers, lower voltage,

insulated bus bars, internal barriers

Faster over-current protection,

energy shunting devices

Signage, training, indicating lights

Maintenance switch, specific work

practices

PPE per applicable standards,

temporary barriers

Hierarchy of Hazard Control

Measures (ANSI Z10)

Examples of Arc Flash Incident

Energy Control Measures

In order of most (1) to least (6) effective

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Summary

30/03/2019 Slide 22

More complex, more data, decisions, judgement, knowledge, i.e.… more risk required for the new accuracy

• Inputs � wide variance in Iarc & Ei

• 2002 based study: possibly, wrong vs. new model

• NFPA 70E: update model with new information?

• Horizontal vs. vertical seems obvious

• Small vs large box seems obvious

• But model reflects a laboratory test protocol… regardless how accurate, it may not be a perfect replica of reality

• How to account for possible error ? Understand the effect of variance & take it into account!

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NFPA 70E 2018 EDITION CHANGE HIGHLIGHTS

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• OHSA is the law

• NFPA 70E outlines how to comply with OSHA’s electrical safety requirements

• OSHA is “What”

• NFPA 70E is “How”

Relation Between OSHA’s Standards & NFPA 70E

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• New Annex Q has been added

• Risk Assessment Procedure requires you to address human error

• Negative consequences of human on people

Human Error

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• The hierarchy moved into standard’s mandatory text

• First priority must be the elimination of the hazard

• Each method is considered less effective than the one before

Hierarchy of Risk Control Methods

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• Article 120 includes a restructured procedure to help how to set a program

Establishing an Electrically Safe Work Condition

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• Table 130.5C is used for arc flash assessment

• Table now applies to the incident energy analysis

Estimate of the Likelihood of an Occurrence of an Arc Flash

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• Use incident energy analysis method

• Table 130.5G moved into standard mandatory text

• Table revised to select gear when using incident energy analysis method

Selection of Arc-Rated Clothing

30/03/2019 Slide 30

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• Employers are required to establish ESP for employees to follow

• This includes training to perform task safely

• NFPA 70E is about preventing the worker from being injured

Electrical Safety Program (ESP)

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