Load Flow

Power Factor Correction

Cole Ferguson · Aug 5, 2016 ·

One of the great things to do after you get a power system study completed, is implement power factor correction. With power factor correction you will be able to properly support the voltage at your site, but more importantly you will likely be able to save some money. Large loads on a utility are charged on power factor, maximum demand and energy use. At home you will only be charged on energy (kWhr).
If you can increase the power factor to unity, you will save on energy, and any reactive power charges. The maximum demand will be slightly helped, but you will more likely need to change procedures to affect this aspect of the bill.

Power Factor Correction Capacitors — That’s a lot of capacitors

What is Power Factor Correction?

Power factor correction is any action on an electrical system that brings the power factor of that system closer to unity.

How does it work?

Power consists of both real and reactive components. The real component of power is the part that does all of the actual work. The reactive component of power is the power generated by the magnetizing current in a motor on transformer. This magnetizing current is necessary to operate machines with alternating current, but does no usable work. Power factor correction works by reducing the reactive power component while maintaining the real power component. This reduces the overall current consumption of your system. The simplest and most common way to improve your power factor is static power factor correction (adding capacitors to your system).

Capacitors

In many electrical systems the current and voltage waveforms are out of sync by a certain amount. In an induction motor, the current lags the voltage. A capacitor however is a purely reactive load, and as a result current drawn by a capacitor leads voltage. The effect this has is that as the alternating current cycles back and forth, it looks like the reactive component of the capacitor current and the reactive component of the motor current “cancel” each other out. You can see this is the phasor diagram below.

Fig. 1 is the phasor diagram of the induction motor. The current lags the voltage. Fig. 2 is the phasor diagram of the capacitor: the current leads the voltage. Fig. 3 is the result of adding a capacitor to your motor circuit: the capacitor current and motor current add together to reduce the phase angle and bring it closer in line with the voltage angle. — Three phasor diagrams of voltage (V) and current (I). Fig. 1 is the phasor diagram of the induction motor: the current lags the voltage. Fig. 2 is the phasor diagram of the capacitor: the current leads the voltage. Fig. 3 is the result of adding a capacitor to your motor circuit: the capacitor current and motor current add together to reduce the phase angle and bring it closer in line with the voltage angle.

The great thing about capacitors is that they are cheap, reliable, and come in many different sizes. If you can’t find a capacitor with the specific size you need, you can combine multiple capacitors in a capacitor bank.

Where to place the Power Factor Correction Equipment?

Since you want your capacitors to draw reactive current away from your motor load, you want to place the capacitors in parallel with your motor. “You can place the capacitors at the equipment, distribution board, or the origin of the installation. Static power factor correction must not be applied at the output of a variable speed drive, solid state soft starter or inverter as the capacitors can cause serious damage to the electronic components. ” (John Ware, IEEE Wiring Matters, Spring 2006).
So there you have it! If you want to perform power factor correction on your system to save yourself some money and possibly increase the capacity of your systems, you have to add capacitors in parallel with your loads. Thanks for reading!
If you like this post but want some actionable advice, tips and information, check out our newsletter. You can sign up here or below.
By signing up you get a free report on what an Electrical Safety Program is, and how to go about building one at your facility.

4 Ways to save money with a power system analysis at your pulp and paper mill

Jeff MacKinnon, P.Eng. · May 31, 2016 ·

Sometimes it seems that the number of requirements for running a plant keeps going up, and regulations keep changing cutting into the bottom line. This is how a lot of clients I have worked with in the past have approached getting a power system analysis completed, they needed labels on their equipment to satisfy the requirements of CSA Z462 and NFPA 70E, so they needed an arc flash study. It was an expense, nothing more.
However, if you define the scope (the first step in performing a power system analysis) smartly, you can duplicate effort without duplicating cost, and use the report to make smart decisions that will either save money immediately or identify capital projects with very fast payback.

1. Reduced number of Electrical Safety Incidents

According to NFPA (source-pdf) the average shock or arc flash injury event can cost $80k in direct costs, if indirect costs are included this can be much higher. However, according to that same paper there are no valid ratios to estimate this.
With a power system analysis in hand, an effective electrical safety program can be developed that will directly affect the number of these incidents. The number of these incidents are typically very low, however the high cost of a single incident will pay for the power system analysis and electrical safety program many times over.

2. Better preventative maintenance program

Competitive pulp and paper mills have at least a preventative maintenance program, and a lot are moving to a predictive maintenance program. The most important part of these programs, like a valid power system analysis, is the quality of input data. When going through the process of validating all the input data for a power system analysis, it would be a simple matter of gathering the information for your maintenance program without duplicating effort. It is likely the same staff that will be doing the work in anycase.
With better information, including short circuit values, expected load flow voltages, etc, you can feed this information into the maintenance program and understand when equipment may fail, allowing you to plan its replacement without affecting the process.

3. Power Quality Improvements

When going through the system and gathering all the necessary input data for the incident energy study, you have all the inputs for proper load flow study, and all you need is some existing load information that can be gleaned from the power meters throughout your mill.
This is where you will see an opportunity to get the most value from the power system analysis. Like most industrial plants you are likely charged:

a energy fee (MW-HR),
a peak charge (rolling MW) and
sometimes a power factor charge.

You can minimize your power factor and energy fees by making sure that you are running your system as close to unity power factor as possible. With a proper power flow study, you will be able to identify areas within you plant that would be best suited for adding power factor correction capacitors and quickly identify the potential payback.

4. Update Drawings of the System

Finally, and likely an over-looked part, is that you will have updated drawings as part of your power system analysis that are very accurate, current, as-built conditions. These drawings are now trusted inputs for any capital or maintenance projects that may take place in the future.
One of the biggest risks to integrating into any existing system, is the quality of the existing documents, and the cost of having a consultant on site developing as-built drawings will increase the cost of a small project quickly. Having these drawings on hand, and assuming you have a document control procedure in place, the consultant replacing a motor or adding a new system will have the best information starting, reducing the design time, construction issues, and start-up concerns.

Next Steps

If you like what you read consider joining our newsletter where you will get every post in your inbox at the start of the month. You will never miss a thing. If you would like to learn more about how a power system analysis can help you manage your system better and safer, contact us here, or visit our services page here.
And if there is someone you think would benefit from this post we appreciate any share on facebook, linkedin or the old fashioned email.

3 Power System Analysis Deliverables To Insist on During Your Next System Study Report

Jeff MacKinnon, P.Eng. · Mar 1, 2016 ·

There are 3 items that must be included and there are a few things that should never be included in a the body of a power system study report. Also – there are some sources of information that are important for you as a client to have to effectively evaluate a consultants expertise in the area. The added bonus of having these on hand as a backup is that you can also use the moment and info as an opportunity to educate the non-electrical workers and managers in your company about things they might not otherwise have cause to consider.

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

Power System Analysis Deliverables

These might be phrased differently from consultant to consultant, but generally speaking the 3 high level deliverables you want included at the end of the project are:

The Power System Analysis Report itself (complete with detailed recommendations of course)
Updated drawings with ALL new information – onelines, switchgear drawings, etc. clearly and explicitly noted and accounted for.
The Power System model within the appropriate existing or selected software of your choice. Ensure it is complete with any custom libraries!

Getting down into some “nice-to-have’s” and 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. For example:
- Labels from the incident energy study
- Updated information for Energized Work Permits
- etc.

Just knowing what the “table stakes” ought to be in any report will give you more confidence and negotiating power to get into the deeper and fuller potential deliverables and to really maximise bang for buck, not t mention the enhanced utility of the report itself.
But enough framing of the situation: lets get into the description of what each of these critical parts are!

Power System Analysis Report

Sure everyone should outline the sections that will be included in the report when scope is discussed, but typically that just means that we only mention the specific study results and a section for recommendations. If this is all you’re doing out of the gates you’ve narrowed the readability and usefulness of the report to wider audiences.
Because the report body isn’t the place to educate the reader about what the different studies are, the pros and cons of different methodologies, or even discussing why it was a good idea to have the study completed in the first place, you need to think about how the work product as a whole will be received when the report gets distributed to people that don’t have an electrical background or who 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.

Seems obvious right? But think back to your own experiences: how many times have you come across a seemingly well written, well thought out piece of work that you just could “get into” because you were missing some element of structure, or frame of reference, or explanatory note to say “this is where you in the information landscape, and this is how we’ll get through this together.”
Once you’ve got that structural component taken care of we can get into the more straightforward meat and potatoes of the report itself. Starting with:

The 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, as well as the standards that were referenced during the work. The sub-headings might vary from project to project, but JMK Engineering’s approach tends to look like:

Purpose
Scope
References
Definitions
Assumptions and Limitations
Project Methodology

A well thought out structure and intro eases a reader into the work. Then we get into…

Study Analysis Sections

Each study (eg. short circuit, protection coordination, incident energ, load flow etc.) – should have their own chapter in the report as each is speaking to a unique aspect and/or audience. Bundling them together is a disservice to anyone using the report after the fact. Each of these should 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
- Important: This is only a summary of the results including separate tables for the warning and the critical items. The point is to present the facts and keep the reader moving.
Study Recommendations
- These recommendations are for the “what needs to be done”, not the “how to actually do it”. It could be that all the critical lines need to be addressed, but it could be a procedural change (eg. “Don’t put the system in that configuration.”)

Following a well written analysis the report should naturally and organically flow into the supplemental information that all the above stems from. This work is included in well structured and well thought out appendices.

Appendices

Who doesn’t love a few dozen (hundred?) pages of detail! The appendices will include the complete analysis outputs for the various studies, including all time current curve’s (TCC’s) for the protection coordination studies. The appendices should also include any pertinent source information that was used in developing the model and report.
Here’s a sample list of appendices JMK has used in past reports:

Original Proposal (including scope, etc – good for recapturing and reemphasizing the origins and assumptions underwriting the project if needed “in the moment”)
Data Collection Sheets
Relevant Correspondence (“Remember that thing, that guy said, about the stuff?”)
- With the client, utility, suppliers and anyone else that provided useful information that was used as part of the analysis.
Incident Energy Labels
What is Short Circuit, Selective Coordination, Incident Energy and Load Flows.
- This is a synthesis of four different articles in one appendix.

Updated Drawings

Next the drawings that are affected by the study and its recommendations need to be updated. We find that drawings typically 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 further reduce and manage risk or potential for mistakes by getting these drawings in sync with what is actually in place.
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 with 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 regulations like CSA Z462 and NFPA70E require it be 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/consultant moves on, or doesn’t have good data retention practices, you will lose this data. Get a copy for your records. Pause. Now say it again with me: “Get a copy for your records”.
Excellent!

Optional Deliverables

This list of deliverables is not exhaustive, and depending on the scope of the power system study you will of course want to include others. Two that I recommend irrespective of specific needs that apply to all projects are: Capital Budget(s), and Electrical Safety Program Update requirements arising out of the report. Let’s dive into each of these next and then bring this post in for a landing.

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 (for example “setting changes to relays”) than 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 didn’t include) them in the RFP. Hopefully this post gives you some deeper insight to know when and how to test whether a low-cost bidder is planning on cutting corners in the short term at the expense of long term value. and it’s a topic we are always interested in talking about in more detail. If you have any thoughts or stories to share, please get in touch, we’d be happy to hear from you!

Originally posted on Sparky Resource

What is a Load Flow Study

Jeff MacKinnon, P.Eng. · Jul 30, 2015 ·

A load flow study is the trickiest of the critical four power system studies: it evaluates your power system’s capability to adequately supply the connected load while staying within proper voltage and current ranges. The load flow study report will determine the voltages and power factor at all your buses, as well as currents or power flow on all your feeders. A load flow study is also called a power flow study.

Why have a load flow study completed?

Completing a load flow study on an existing system will provide recommendations for system operation and optimize the system operation to minimum operational costs. Understanding the power flows on various system feeders will allow the operators to understand if there is spare capacity, if there are areas of the plant that are overloaded, and if there are operational configurations that will save energy and the associated costs.

Energy Savings

There are a few results of the load flow study that will help you understand if the power system is operating in the most efficient manner. With the rising cost of energy, it makes sense to ensure that the power system is operating in the most efficient manner for as many different configurations as possible.
One way to do this is to add power factor correction to the system that will limit the system’s energy consumption. With the load flow study you will be able to understand where a single bank of power factor correction capacitors will make the best difference.
A larger energy cost saving measure is removing new peak demand from the system. A load flow study will allow operations to understand the best way to limit the impact of a new demand peak.

Capital Expansion or Contraction

Destroyed electrical outlet and sign — Sometimes removing the lights is the best option.

The one sure thing about an operating facility is change. Whether there are plans for expansion or system contraction, it makes sense to have a load flow study available to help understand which feeders have spare capacity. If system contraction is needed, a load flow study will allow the engineers to determine which feeders can be used to consolidate the remaining load.
Consolidating existing equipment loads to a couple of larger transformers will allow the transformers to operate near their optimal efficiency. This will also allow very lightly loaded transformers to be removed from the system, removing the magnetization current that is wasted energy.

When to have a load flow study completed?

The information that is critical from a proper load flow is the voltages and power factor at all your buses, and currents or power flow on all your feeders. With this information you will be able to make important decisions on where to add or remove load, and where power factor correction can be added to increase the efficiency of your system.

How to get one completed?

As with other power system studies, the hybrid model as outlined in Getting a Power System Study Completed is the preferred method to get a Load Flow Study completed at your facility. Understanding how the facility operates is critical to creating an accurate load flow model.
We suggest to start with the most common system configuration that has meter and motor information. When the model is developed, and matches the system configuration, then the model can be built upon for the less used switch configurations.
If you liked this article be sure to share with the buttons below and sign up for our newsletter where you will get these posts in your inbox and special offers. Be sure to follow us on Twitter and like our page on Facebook.

Power System Study Scope

Jeff MacKinnon, P.Eng. · Jun 25, 2015 ·

Understanding what you will be primarily using the model for is critical.
In some cases the thought is to develop the model as part of the arc flash study and comply with NFPA70E or CSAZ462. This is not a bad idea, even though you are not in compliance – they are standards not codes. When you are completing a study for incident energy purposes, the model will be set up to ensure that you are getting worse case scenario energies. The scope will be different if you are sizing equipment for a addition to your facility.

Large Project — Flickr – No matter if your project is big or small, understanding the scope will make the process smoother.

In Power System Studies – The Why and How, I discussed all the reasons why you may need a new or updated power system study at your facility and in Power System Studies – The Critical Four we talked about the four studies I want to see every facilty address. However, you may have constraints either time or money that don’t all you to have all for completed at the same time, or you may have parts of you plant completed and others that need to be updated. The first step before starting any data gathering is to determine what you need completed.
For example, if you decide that you want to have an incident energy study completed for your facility, but don’t have any power quality concerns, you will only need to gather data for the short circuit, protection coordination and operating scenarios for the incident energy study. This has been detailed here.

Power System Study Scope Development

Don't let the power system study scope be a moving target — Nailing the moving target – Flickr

For any power system study project there are five areas that need to be addressed during the planning stage, they will determine how the project will be executed they are:

Project Scheduling
Data Gathering and verification
Model Generation
Report including the following sections:
- Short Circuit Study Results
- Protection Coordination Study Results
- Incident Energy Study Results
- Load Flow Study Results
- Recommendations to mitigate problems found in the results
Presentation of results

Project Scheduling

Determining the required project schedule and deadline will detemrine the resources required to execute the project. Depending on the budget available, this timeline can be moved by adding or removing resources. This is also the time to corrdinate facility outages with other planning groups. It is always better to know when an outage is planned and use the same time than adding another outage to the system.

Data Gathering and Verification

This is where you plant your data collection effort. Check out the link to learn more about this.

Model Generation

Does your existing drawings have a naming system that can be used by the model, does your company have a standard? Is the standard documented? Knowing this remove confusion when discussing system components for the different system configurations, etc.

The Power System Study Report

The report should include sections for all the studies that you are completing and recommendations for any areas of concern:

Short Circuit Study Results
Protection Coordination Study Results
Incident Energy Study Results (This is not an arc flash study – will be explained in a future post)
Load Flow Study Results
Recommendations to mitigate problems found in the results

Presentation of Results

Who will be interested in the results of the study? Can you get them all in the same room? How is the best way to present the report.
What you will be trying to avoid is a binder getting dusty on a shelf in an engineers office. I talked briefly why most of the groups in your facility should be interested, and how they can leverage a good study and make their business area more reliable.

Conclusion

When the sower system study scope is complete it is time to get started deciding how to execute the project. There are three different ways that this can be done, and next week we discuss the pros/cons of each, and some tips on how to use them successfully.
They are:

Complete the project internally
Outsource all the work
A bit of both.

If you liked this article be sure to share with the buttons below and sign up for our newsletter where you will get these posts in your inbox and special offers. Be sure to follow us on Twitter and like our page on Facebook.

Data Requirements for Power System Studies

Jeff MacKinnon, P.Eng. · Apr 3, 2015 ·

Now that we have an understanding about the importance of good data collection for power system studies, and how to prepare a plan for data gathering, now we need to understand exactly what is needed for each power system study type and specific pieces of equipment. However, there is some information that is needed no matter what study is being completed.

Pole mounted utility transformers. — The size and type of the utility transformers make a huge difference

What do they all need?

Utility information
Nominal system voltage levels
System configuration with the following equipment:
- Transformers (with impednance, voltage and configuration),
- Configuration switches and circuit breakers
- Switchgear, mccs, switchboards, etc down to the voltage level you are interested in
Any large motors and other generation on the site.

With this minimal information you can prepare an adequate short circuit study that will give you values for the short circuit on any of the buses above. These will be very much worse case as we haven’t gathered any additional impedance information. This study would be useful for design and specification purposes when you are purchasing equipment for a new facility.

Short Circuit

What information needs to be added to get a decent short circuit, well it is everything above and the following:

Distribution equipment short circuit withstand and full load information
Transformer ratings
Protection equipment manufacturer information, complete with full load rating and short circuit withstand ratings.
Cables connecting distribution equipment, complete with size, type, configuration and length
Lumped motor and non-motor loads at all distribution equipment

With this information you will be able to determine the worse case fault scenarios based on your system configuration and determine if there is any equipment that hasn’t been designed to withstand that level. If there is, this is the first thing that must be addressed in your facility.

Protection System

The additional information that is required for your protection system includes everything that is needed to determine how your protection is going to activate in the event of a fault as determined by the short circuit study.
For this you will need to determine the following:

Trip characteristics of all relays
Tripping times for all breakers
Complete manufacturer information for the fuses in your system
Manufacturer information for all moulded case breakers
Any large motors, and their protection broken out. This is to ensure that the protection is coordinated with the worse case starting current.
For large motors the interial load, and starting times may be required, along with any design type information.

With this information in the model, time current curves, commonly called TCCs can be developed and reviewed to determine if the system will operate in the event of a fault as intended. If there are any overlapping areas that may be cause for concern, this is where they should be addressed. If there is a fault, predictability in how it will be cleared is very important in the aftermath. If multiple protection devices activate it is much harder to determine the cause if there isn’t much visable damage.

Incident Energy

Getting into the meat and potatoes of the studies. As I mentioned in the previous episode, incident energy, and the resultant arc flash risk analysis, is the single most cited reason when I ask why the prospective client is interested in getting a study completed. This is where a lot of time and care needs to go into gathering the data necessary for the study, and where the previously stated numbers related to time come into play.
Along with all the information that was gathered for the barebones short circuit and protection coordination, more detailed informaiotn on the imedances withint the system and loads need to be gathered. All information, for any place that the electrical safety program required a detailed label, based on whether or not there will be energized work, needs to be put together.

What type of loads?

This information amounts to the following, starting at the load. All motors 25hp and above need to be broken out. The actual size whether it is 25hp or 50hp isn’t as important as they are broken out. Induction motors contribution fault current for short periods of time, and the magnitude is proportional to the motor size and intertia. This fault current, is not “seen” by the protection relay upstream and doesn’t account for how quickly the protection will clear the fault, however it does contribute energy into the incident energy value. However, it is not a linear relationship, therefore a large number of small motors will not contribute the same values as a single large motor, therefore it is important to break out the larger motors, I like to use 25hp as the break point, and then lump the remaining motor load.

How are the loads fed, what is the impedance?

The cable information, including the size, configuration, raceway material and length is needed from the load to the MCC, or distribution panel. This all contributes to the overall impedance of the cable, and affects how much energy that motor can contribute. If the length is hard to determine, walk it down and err on the shorter side. Since this fault current doesn’t affect clearing time of the protection, erring on less impedance will give you a worse case incident energy everytime. In a future episode I will discuss why this is important, in short it has to do with the time portion of the incident energy equation.
The motor protection, including overloads and MCP is good to have here, it is not critical, but since you will likely be in the bucket gathering the data, it is better to have it now. It will be important if qualified workers are needed to complete energized work at a local motor disconnect, or within the bucket itself.
If the detailed cable information mentioned for the motor feeds wasn’t gathered during the short circuit it is important to get it here.

Load Flows

When you have all this information, the load flow is mostly complete, we need to get into the operational details. We have already mentioned the motors, and breaking them out, now we need to start thinking about the non-motor loads, and just as importantly, what is a good “demand factor” that can be applied to these.
For example, for all the other studies we assume that that motor or load is running at 100% kW, however this is rarely the case. For an accurate load flow, load factor percentages need to be added to determine the loads and then the resultant report can then be checked against any metering information that you may have at your facility to determine that it is accurate.
If this information is hard to come by, a good starting point may be as follows:

Motors greater that 250hp – 100%
Motors 100hp to 250hp – 75%
Motors less than 100hp – 50%
Non-motor load – 75%

From this iterations can be made to get closer to actual values that can be used as a basis of the report.

Conclusions

Now that you know why you may need a power system study at your facility, how to get started with getting the studies completed, and with this series how to gather the data necessary for great reports. The next step is to get started.
If you need assistance send us a email with a brief description of your system and how to get back to you. We look forward to hearing from you.
If you liked this article be sure to share with the buttons below and sign up for our newsletter where you will get these posts in your inbox and special offers. Be sure to follow us on Twitter and like our page on Facebook.