JMK Engineering Inc.

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Arc Flash Risk Analysis

What Can I Do With Incident Energy Studies?

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esp into featured imageToday, I will outline three things you can do with a completed incident energy study. Completing these tasks is an important part of any electrical safety plan, and will reduce the risks to employees performing work on energized equipment. This will also reduce the risk of an arc flash incident occurring.

Identify Key Problem Areas

An incident energy study will show you where the incident energy is dangerously high in your facility. Now that you know the incident energy on a particular bus is high, you can analyze your power system with this information in mind, and try to answer the following two questions:

  1. Why is the incident energy at this location so high?
  2. Can the incident energy at this location be lowered somehow to provide a safer working environment?

Establish Working Boundaries and Select Warning Labels

arc-flash2
An example of a warning label

Once you’ve answered the questions about your key problem areas, you might determine that the incident energy level cannot be reduced any farther. From here, what you can do is use the information in your incident energy study to establish safe working boundaries and acquire warning labels. The incident energy study should indicate the likelihood of an arc flash event occurring. Knowing the risks, you can assign appropriate working boundaries for the tasks involved with energized equipment. The incident energy study should have different “levels” assigned to each piece of equipment that is a part of the study. These levels correspond to recommended working distances, and you can use these levels to label all of your equipment so that every worker understands the risks of working on energized labelled equipment.

Select Appropriate PPE For the Job

Now you can use your newfound knowledge of the safe working boundaries to select the appropriate PPE for any job that takes place in your facility. The same levels that you used to

An example of PPE

determine working boundaries can also be used to determine PPE requirements. If for example you must work closer than the recommended working boundary, the incident energy study will recommend the level of PPE required for doing energized work at different working distances.
In order to determine what PPE you need, you’ll have to use the relevant standards. CSA Z462 in Canada and NFPA 70E in the USA both have extensive tables describing what
appropriate PPE is for the various levels of incident energy on a work site. It is important to also adhere to any and all local and regional standards for your area.
An incident energy study is required for determining safe working boundaries and PPE for the work site. Thanks for reading! If you enjoyed this article, sign up for our newsletter for more content like this, and share this article with your colleagues with buttons below.

Power System Study Deliverables

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Now that you have decided on the project framework that you are going to go with and you understand the scope of the power system study, you need to prepare the list of deliverables.

Power System Report drafting
Let’s outline the power system study report

There are 3 items that must be included in every report, and there are some things that should NEVER be included in a power system study report body. There are some sources of information that are important to have as backup to both you as the client to evaluate the consultants expertise in the area, and also to educate the non-electrical workers and managers in your company.

Power System Study Deliverables

The 3 overall deliverables that should be included at the end of the project are:

  • Power System Study Report, complete with recommendations
  • Updated drawings with any new information – onelines, switchgear drawings, etc.
  • Power System model in the software of your choice – complete with any custom libraries.

Depending on the scope of the study, you may want to include the following:

  • Capital Budget estimates to implement selected recommendations
  • Updated Electrical Safety Program Documents
    • Typically labels from the incident energy study
    • Updated information for Energized Work Permits

Now lets describe the critical parts of each of these.

Power System Study Report

We outlined the sections that will be included in the report when we discussed scope, but there we only mentioned the specific study results and a section for recommendations.
The report isn’t the place to educate the reader about what the different studies are, the pro and cons of different methodologies, or discussing why it was a good idea to have the study completed. If the report will be distributed to people that don’t have an electrical background and need to be brought up to speed, here’s the tip I use at JMK Engineering:

Include appendices with articles and short whitepaper reports describing what the studies are and how they can be used. This keeps the report on topic, but expands the audience of the complete report.

Introduction

The introduction is the place in the report where the reader is orientated as to what this report is all about. The introduction should include the purpose and scope of the report, the methodology used to gather data and study the system, and standards that were referenced during the work. The sub-headings include:

  • Purpose
  • Scope
  • References
  • Definitions
  • Assumptions and Limitations
  • Project Methodology

Study Analysis Sections

Each study – short circuit, protection coordination, incident energy and load flow – will have their own chapter in the report.  Each of these will have the following sub-sections:

  • Introduction
    • Study specific scope items
    • Study specific source information – utility supply, motor loading assumptions for load flow, system configurations reviewed, etc
    • Thresholds used for warning and critical for the results.
  • Study Results
    • This is only a summary of the results including separate tables for the warning and the critical items.
  • Study Recommendations
    • These recommendations are for the what needs to be done, not the how.  It could be that all the critical lines need to be addressed, but it could be a procedural change (don’t put the system in that configuration)

Appendices

This is where the report starts to grow. The appendices will include the complete analysis outputs for the various studies, including all TCCs for the protection coordination studies. The appendices should also include any pertinent source information that was used in developing the model and report. Here is an example list of appendices that I have included in past reports:

  • Original Proposal (including scope, etc)
  • Data Collection Sheets
  • Relevant Correspondence
    • With the client, utility, suppliers and anyone else that provided useful information that was used in the analysis.
  • Incident Energy Labels
  • What is Short Circuit, Selective Coordination, Incident Energy and Load Flows.
    • This is 4 different articles in one appendix.

Updated Drawings

Next the drawings that are affected by the study and its recommendations need to be updated. What I have found is the drawings lag behind the changes in the field over time, and during the data collection effort we find a number of conflicts, equipment added or removed and settings changed.  The power system study is the perfect opportunity to as-built all these drawings.
The oneline is always caught, but there are other drawings that should be looked at for inconsistencies.  These can include:

  • Threeline diagrams
  • Motor Schematics
  • Switchgear and MCC Drawings
  • Panel Schedules

Power System Model

If you are having an outside resource develop the model, we still recommend you receive a copy of the model and any custom library items electronically. Ideally this will be included on a thumbdrive and included in the report as an appendix.  The best reason for this is that the power system study report is not a static thing, as the system changes it will be updated, and per CSA Z462 and NFPA70E it should be updated no less than every 5 years. After doing all the work – and spending the money – to get the original completed, it is much easier to update with changes than go through the entire process every 5 years.
If the contractor moves along, or doesn’t have good data retention practices, you will lose this data. Get a copy for your records.

Optional Deliverables

The list of deliverables is not exhaustive, and depending on the scope of the power system study you will include others.  Two that I recommend are capital budgets and electrical safety program updates.

Capital Budget Development

You likely have a capital budget cycle that is used to determine what capital projects will be completed in the coming years.  Based on the recommendations outlined  in the report, there are typically additional engineering and installation that will be needed to fulfill the recommendations and make the system safe. To develop these budgets there is some initial engineering design required, but the entire design does not need to be completed in most cases. To present a complete package to management, and allow business decisions to be made, the capital budget report should include the following for each recommendation:

  • Recommendation and why it is needed (Scope)
  • Options – if there are any
  • Capital cost for each option in today’s dollars
    • This should include engineering, procurement, and installation/construction

If there are similar recommendations, like setting changes to relays, these can be grouped.

Electrical Safety Program Updates

If you included an incident energy study in your report, and you have an existing electrical safety program, you will want to make any necessary updates. This may include adding information to the energized work permits, adding new labels and updating the training information

Conclusion

The deliverables related to a power system study are not just labels and an output for the software. To be useful, informative, and actionable we need to include everything mentioned above.  A good consultant will include all the critical deliverables even if you haven’t included them in the RFP, however the lowest price may cut out most of them and provide the bare minimum.
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Power System Studies – The Why and How

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In the first part of the Power System Study series I told you what a power system study is, and in the second I described what power system analysis I consider critical for every facility, plant, building, etc, no matter how large or small.
These are:

Now, assuming you have these studies in your hands, what do you do with them? In Part 3 I will give ideas on why power system studies are important for your facility and business, and how different areas of you company can benefit from a comprehensive power system study.

Who can leverage a power system study

It’s not just engineers

Once you have a power system study in place you can starting thinking about how to leverage it and make decisions to improve your facility.
There are four perspectives that the study can be viewed from, and most companies have them.  Whether it is one person with many hats, or groups of dedicated personelle.
They are

  • Management
  • Operations,
  • Maintenance,
  • Capital projects.

Management

With the Incident Energy report in hand, critical information can be added to the Arc Flash Risk Assessment and areas that are found to be high risk can be looked at closely.  Mitigation techniques can be implemented in these areas starting with eliminating the risk entirely, or adding engineering controls that lower the incident energy to an acceptable range. This may be a relatively simple setting change in a relay, or replacing an old protection scheme with a modern relay with multiple sets of settings.  One for normal operation and another for energized work.
Management will integrate this information into the facility’s electrical safety program, and the general safety program.  They can update the risk assessments associated with their electrical system.

Operations

Second,operations can use the reports to identify areas that are a higher risk to cause outages, and determine how the system reacts to faults.  The two studies of particular interest are the protection coordination and incident energy.
The protection coordination lets the operator know what areas of the facility will be affected in the case of an outage, and if the area is too large, or not large enough, modifications can be made to optimize the selective coordination scheme.
The incident energy study helps the workers on the floor stay prepared, within the greater electrical safety program.

Maintenance

Maintenance will look at the short circuit and load flows to help prioritize where preventative maintenance budgets should be focused. The short circuit study will determine if there is any existing equipment that is over-dutied. Meaning that it is not designed to handle the fault currents that it could be subjected to in the event of a bolted fault.  If there is any over-dutied equipment identified, maintenance will start the process of replacing, or mitigating the fault currents by changing system configuration, such as not operating with transformers in parallel, or adding current limiting reactors that increase the short circuit impedance on the system.
The load flow report can help schedule maintenance schedules for major equipment such as motors and distribution transformers.  If a newer transformer is close to its design load most of the time, versus a older transformer being lightly loaded, the probability of failure may lean toward replacing the newer transformer before the older one.  Without the load information the older transformer would be replaced sooner, costing more from the maintenance budget if the newer transformer failed around the same time.

Capital Projects

Finally capital projects can use the model to make improve decisions for capital improvements. When capital improvements are in the early stages, modifications to the greater power system, other than the new equipment being added, is sometimes neglected.  This oversight may increase the cost greatly when the service entrance needs to be replaced, or other major changes have to be made.
With a current short circuit and load flow study, most of these issues can be accounted for early in the capital project cycle and power system improvements can be accounted for at the start.  Without a current power system study you will not know, and it will likely cost too much to have one completed just for a capital project budgeting.
Along the same lines the model can be used to save money, one way is by making improvements to the power system to increase efficiency.
Utilities, especially when they are dealing with a large load, may have power factor and demand changes that are much higher that the energy charge.  With a load flow study in hand, it is a relatively easy task to determine where pf correction could be added to keep the PF charges low, or if there are any buses in particular that can be controlled differently to prevent new demand charges.

Conclusion

This concludes our three part series on Power System Studies. If you missed Part 1 on Monday, it defines what a Power System Study is, and Wednesday I talked about what the critical power system studies every facility needs.
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