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WEBINAR EXECUTIVE SUMMARY

IEEE 1584 REVISIONS

Significant changes on the way for arc flash calculation analysis.

KEY TAKEAWAYS

  • The New IEEE 1584 should be more accurate and complex than the 2002 version.
  • The new version of the guide adds three new electrode configurations.
  • The new model introduces a new calculation method.
  • IEEE 1584 2.0 has a number of new variables improving calculation accuracy.
  • Considerations for implementing the new IEEE 1584 in the real world.

In 2002, the Institute of Electrical and Electronics Engineers (IEEE) developed a model for incident energy, which was published in IEEE 1584-2002: Guide to Arc Flash Calculations.

The IEEE is now in the process of updating that guide, with IEEE 1584 2.0 expected to be released in late 2018 or early 2019. The new standard is expected to be more accurate than the original version, accounting for more variables within the hazard-causing event. Although it is more representative of actual conditions, it doesn’t account for all real-world situations and use cases that can occur.

Presenter

Marcelo E Valdes

Electrification Products division, ABB

Arc Flash Codes & Compliance

What you need to know to deliver both protection and performance.

In our recent webinar, Marcelo Valdes reviewed the major changes in IEEE 1584 2.0 and shared considerations for implementing the new standard in the real world. Watch the webinar and download a pdf of the webinar to learn more as you dive into this interactive summary.

IEEE 1584 2.0 is a more accurate but more complex model than the 2002 version.

When it was released in 2002, IEEE 1584 defined the science of arc flash for the process of risk assessment when working near electrical energy operating below 15,000 volts. But this was not intended to be a perfect definition of all real-world situations. It was an estimating tool for situations, most applicable where the situation was similar to the test protocol used. The new testing project had increased funding and more tests and allowed for a more varied set of test protocols. This led to a more complete, more accurate, but more complex model that improves upon the science, yet still has the potential for accurately reflecting real-world situations in some cases.

Testing and Complexity Differences in IEEE 1854

Area of Difference 2002 Version Version 2.0
Funds for testing $100,000 Several million dollars
Number of experiments < 300 Approximately 2,000
Pages of math formulas Approximately 3 page of math formulas 17 pages of formulas, coefficients, and exponents
Variables Includes more variables for a more representative model of actual conditions

“[IEEE 1584 2.0] will not be a perfect replica of the real world. It’s important that people realize what the potential errors are and how they relate to the real-world situation.”

– Marcelo E. Valdes P.E, Electrical Products Division, ABB

The new version of the standard adds three new electrode configurations.

The biggest difference between the current model of IEEE 1584 and the new model is the number of electrode configurations: the electrical conductors that can sustain the electric arc. Three new configurations were added, along with a new direction allowing for horizontal electrodes.

Five Electrode Configurations and Considerations

  • Assumes the arc is aimed within the box, reflecting heat and smoke created by the event within the box, with the plasma not directed at the worker.
  • No attempt was made to take into account materials within the box, such as cables and insulating materials, that could impact the direction of the energy, or possibly creating more hazard than the model predicts.
  • Assumes electrodes are near the bottom of the enclosure or there is a barrier, constricting the arc, generally resulting in a higher level of energy directed toward the worker.
  • Common in larger equipment, an example may be switchgear runbacks.
  • In this configuration the electrodes act to propel the arc (plasma) toward the worker.
  • Typically used outside, such as in outdoor switch yards.
  • Electrodes are vertical, but the worker may be directly beneath them; whether the electrodes are perpendicular or parallel to the worker may be more important than whether they are vertical or horizontal!
  • Tested with electrodes in a horizontal row.
  • An example of where real world is different may be transformer terminals arranged in a triangular pattern. The arc may be more stable, will the energy be more? How much more if so? The guide does not address this!

The old model focused only on vertical electrodes, while the new model adds in horizontal electrode configurations and vertical with constricted space at the end. With horizontal configurations, the worker is expected to be perpendicular to the electrodes and more likely to be in the direct path of the plasma in an arc flash event. The worker is parallel to the electrodes in most, but maybe not all, vertical configurations, which can decrease the impact of the heat and plasma.

In any one cubicle or space the worker is exposed to there may be multiple electrode configurations, each with different arcing current and incident energy predictions. Each may need to be considered for proper risk management implementation.

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The new model introduces a new calculation method.

The new model uses a two-step process to calculate arcing current, incident energy, and arc flash boundary. The calculation uses a different method for 600 volts (V) and higher and 208V to 600V. Similar in concept to the old model, which set the threshold at 1000V and lower, and 1000V and higher, this new model differs in that the results are not discontinuous as they were previously. The new calculation also allows for correction factors for enclosure size variation from the normalized values used for the initial prediction.

Working distance guidance is similar to that from before but a clear definition of a minimum distance for which the calculations are applicable was added (12 inches). For most work, the recommendation is that the working distance should be 18” since 24” implies the electrodes are deep within a cubicle where they are hard to reach. A risk assessment can best determine the right working distance, which should be no less than 12”.

When developing new labels, it should be considered that the label is valuable data to be used for a future risk assessment and PPE selection. Confusion caused by multiple labels or excess information or complexity may increase the risk of an error. The label should generally reflect a realistic and conservative assumption of the worst-case scenario for that piece of equipment.

“Realize that the investments you make to increase safety can also result in better maintenance, communications, HMIs, diagnostics and controls.”

– Marcelo E. Valdes P.E, Electrical Products Division, ABB

IEEE 1584 2.0 has a number of new variables improving calculation accuracy.

The new model includes a number of new variables, as well as some changes to existing variables, that improve the overall accuracy of the calculation.

The new model will still yield an arcing current, incident energy, and an approach boundary, just like in the old model, but with more accuracy.

Calculation variable differences: Current model vs. new model

Existing variables
• Gap, typically equipment-driven
• Working distance
• Operating voltage
• Available short current
• Box (yes/no)
• Grounding
New variables
• Electrode orientation
• Electrode environment; e.g., barriers
• Box size considerations
• More variable gap considerations
• Arcing current
• Incident energy
• Approach boundary
Removed variables from 2.0
• Grounding; determined not to have an impact

Considerations for implementing IEEE 1584 in the real world.

Guidance in IEEE 1584 is more accurate because of the significant number of tests run to develop the new standard. However, even with updates and changes in the model, it does not completely reflect all real-world applications.

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A number of ways to approach application in the real world are:

  • Understand the test protocol and model and how they compare to the real world and the real equipment that needs to be modeled.
  • Know that protection sensitivity and speed become more important, especially as some modes of arcing faults will yield more energy and potentially less arcing current.
  • Use Prevention through Design (PtD) techniques, products, and processes.
  • Understand the direction of possible error and the effect of the difference, and determine how to take that into account.
  • Decrease exposure of workers and keep them further away from live conductors, when possible, using communications, a human-machine interface (HMI), diagnostics, controls, and conditioned-based maintenance.
  • Turn off equipment, use proper lockout and tag-out techniques. Look to personal protective equipment (PPE) as the last resort.

Note: Direct Current (DC) is not yet included in the guide but is under consideration. Those interested in this topic should contact the IEEE 1584 working group to provide input.

Hierarchy of Hazard Controls and Examples of Arc Flash Incident Energy Control

Hierarchy of Hazard Control Measures (ANSI Z10) Examples of Arc Flash Incident—Energy Control Mechanisms
1. Elimination of the Hazard Secured and Verified De-energization
2. Substitution of Less Hazardous Equipment or Materials Smaller Transformers, Lower Voltage, Insulated Bus Bars, Internal Barriers
3. Engineering Control to Reduce Exposure or Severity Faster Overcurrent Protection, Energy Shunting Devices
4. Warnings, Signs, and Other Communicators Signage, Training, Indicating Lights
5. Administrative Control, Including Safe Work Practices Maintenance Switch, Specific Work Practices
6. PPE PPE per Applicable Standards, Temporary Barriers

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