• Skip to primary navigation
  • Skip to main content
  • Skip to primary sidebar

JMK Engineering Inc.

Solving problems and asking the right questions

  • Home
  • About Us
    • Jeffery MacKinnon, P.Eng., PE
    • Mission
      • Founding Principles
    • Areas of Expertise
  • Webinars
  • Blog
  • My account
    • My Courses
    • Member Benefits
  • Contact
  • Show Search
Hide Search
You are here: Home / Archives for Jeff MacKinnon

Jeff MacKinnon

Data Requirements for Power System Studies

Jeff MacKinnon · Apr 3, 2015 · Leave a Comment

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 pLineup ready to start gathering data for a power system study.lay.
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.

Advertisements

Data Collection For Power System Studies

Jeff MacKinnon · Mar 2, 2015 · Leave a Comment

What Is Needed When Gathering Data For Power System Studies

Data Collection is about gathering the data necessary for building an accurate model of your power system. This model will be the basis for the various studies that we mentioned last week, and without accurate data the model will not be as useful as you need it to be.

Time to stat gathering that data.
Time to stat gathering that data.

Why having complete and accurate data is important

First the results from the power system model are only as good as the data that is used to create it. If the data is not correct, then the model that is created will not be accurate. In fact incorrect data will lead to poor results in the incident energy study which is very sensitive to the fault levels on the system. It is very important to get accurate impedance information, this includes cable configurations, transformer data, etc.
Collecting the data for the first time is a very labour intensive prospect, and can account to 50% of the cost of getting the initial study completed.  That’s one of the reasons I mentioned before about getting the data together, and getting more than one report completed at the same time.  The incremental cost in negligible compared to the total cost of the project.
When your facility has good single line diagrams, manuals, and data in other forms, this will speed up the collection process.  However it is always a good idea to verify all this data in the field, especially for larger, active facilities where changes are being made on a constant basis.  When this is completed once, the model can be used as a change management tool. One of the software vendors have a great webinar describing how you can use their software to manage change in the entire facility

How long to expect?

Data Collection can cost a lot of money
Managing cost and time is important

You can expect that the data gathering stage of the project will take about 2hours for every substation, switchgear lineup and MCC, and 0.1 hours for every load, including motors, panels, etc.  If your facility is spread out or has a lot of specialty equipment these numbers may need to be increased.  This will give you an idea on how long you can expect to take to gather all the data for your facility.
We have included forms in the content library that will help you gather this information. We based the information required on the recommendations of ETAP.

How much do you need to gather?

Depending on what set of studies you are planning to have completed, the detail of the data that needs to be gathered will be slightly different. It is my opinion that you have at least the 4 studies completed that we mentioned last week in, The Critical 4, they are Short Circuit, Protection Coordination, Incident Energy and Load Flow. These 4 studies build upon each other, and as such they need increasingly more and better detailed information.  Lets start at the top, what do they all need?

  • Utility information (MVA, X/R min and max)
  • Nominal system voltage levels
  • System configuration with the following equipment:
    • Transformers (with impedance, voltage and configuration),
    • Configuration switches and circuit breakers
    • Switch gear, 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.

What’s Coming Up

On Wednesday I will lay out the specific data that is required for each of those critical four.  They all build upon each other, and will require collecting data in the field and interviewing operators and maintenance to understand how the facility operates.
If you liked this article be sure to share with the buttons below and sign up for our newsletter (the form is below) 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.

3 tips to use electricity safely at home

Jeff MacKinnon · Nov 24, 2014 · Leave a Comment

The more connected we become, and the more DIY projects we take on, the more aware we need to be of the hazards of electricity. There are two hazards directly associated with electricity: shock and arc flash.  This said, there are many more indirect electrical hazards that can arise from misapplication, such has heat causing fire from overloaded circuits.
Staying safe with electricity at home is really easy; you should never do electrical work by yourself.  Always have a qualified electrician do any work in your home if it requires removing a plate or fixture.  There are three things that you need to do to stay safer at home:

1. Only plug in approved appliances

Recognized-Certification-Marks-October-2014Counterfeiting is a much larger concern in Canada than most realize. This has nothing to do with that movie you downloaded in university (or last night). We are talking about counterfeiters importing common electrical equipment like phone chargers, lamps, etc. These devices are likely not approved, tested or suitable for use.  They may over heat and cause fires, or become a shock hazard.
Whenever you buy something to be plugged into a wall outlet, be sure that the device has a suitable, approved mark.  For example, ESA in Ontario has a great list of all the recognized certification marks in Ontario http://www.esasafe.com/consumers/productsafety/marks

 2. Don’t overload your circuits

Overloaded Power Bar
In North America, the typical wiring in a house is designed to carry 15 Amps – anything above that will cause the breaker for that circuit to trip.  The wire in an extension cord or power bar, on the other hand, is designed to carry much less, depending on the gauge of wire used.  Overloaded wires will heat up, and can cause fires.

3. Household safety inspections

Develop a routine where you go around the home and check your various electrical components to be sure they are still safe for use.  This includes the cords on your TV, appliances, lamps, etc, any extension cords and your GFCI and AFCI breakers and receptacles
GFCIInspect all your cords.  Look for damage to the cord in the form of nicks, scratches or bare wires.  A cord that is warm to the touch is a sign of overheating.  In the case of an extension cord, unplug and replace it, or have a licensed electrician fix or replace the cord.  When discarding, be sure to cut the cord through to ensure that an unsuspecting person doesn’t try to use the defective equipment.
Test your GFCI receptacles by pushing the TEST button. If it works properly you will hear a click and the power will be turned off. Press the reset to put back into service.  If you have GFCIs in your panel, do the same thing.  If it is working, you will see the breaker trip.  Reset the breaker and you are done.
AFCI breakers and receptacles are tested in the same way as GFCI.

Electrical Safety in General


In general, electrical safety at home is all about using certified/marked appliances, with maintained cords, without overloading the circuits at home.  By doing this you will lessen your chance of an electrical fire, or shock to you or your loved ones.  If you have any questions, please comment below or post a question in our new forums.  If you don’t want to register, please tweet us at @sparkyresource
If you found this article useful, please sign up to our newsletter and share it with your networks.

  • « Go to Previous Page
  • Go to page 1
  • Interim pages omitted …
  • Go to page 4
  • Go to page 5
  • Go to page 6

Primary Sidebar

Cart

Privacy & Cookies: This site uses cookies. By continuing to use this website, you agree to their use.
To find out more, including how to control cookies, see here: Cookie Policy

Copyright © 2019 · Monochrome Pro on Genesis Framework · WordPress · Log in

  • Accessibility
  • Terms of Service
  • Privacy Policy
  • Book a Free Consultation
  • Account details
  • Orders