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Design calculations

Design calculations establish minimum guidelines and requirements for generating electrical calculations on projects. Electrical calculations should be made for all projects that include electrical components and should be filed in the project notebook.

Electrical Design Calculations Needed For Projects
Electrical Design Calculations Needed For Projects

Design calculations may be made either manually or by computer programs. At a minimum, the following types of calculations should be made where applicable:

  1. Load calculations
  2. Conductor sizing
  3. Conduit sizing
  4. Motor branch circuit sizing
  5. Power factor improvement
  6. Transformer primary and secondary circuit sizing
  7. Voltage drop
  8. Motor starting voltage dip
  9. Short circuit analysis
  10. Lighting levels
  11. Grounding in substations (where step potentials are of concern)
  12. Harmonic distortion analysis
  13. Cable pulling calculations
  14. Generator capability/motor starting.

Load

Load calculations should be made using applicable sections of NEC Articles 220, 430, and other sections of the NEC.

The following load calculations should generally be used for sizing:

  1. Feeder conductors and protective devices
  2. Transformers
  3. Panelboard and switchboard main busses
  4. Motor control center components
  5. Service entrance devices and conductors
Load calculations must include all loads. They should be made by summing all of the loads (using appropriate diversity factors allowed by NEC Article 220) that are connected to each panelboard, switchboard, and motor control center.

An allowance must be made for future load growth. The loads for each branch of the distribution system can then be summed back to the service entrance equipment.


Generator Sizing

The following information is intended to familiarize the design engineer with terms used by generator sizing software and underlying formulas.

Generator single or multi-sets must be sized to supply maximum starting (SkVA), stead-state running (RkVA) and non-linear (GkW) demands of connected and future electrical equipment.

Information critical to the sizing and selection of generator single or multi-sets include:

  1. Environmental conditions: elevation, temperature, indoor or outdoor
  2. Noise abatement requirements: mufflers, enclosure, silent models
  3. Fuel: diesel, gasoline, natural gas
  4. Fuel storage: skid mounted tank, day and remote tanks
  5. Cooling: liquid cooled radiator, forced air
  6. Voltage regulation: maximum allowable voltage dips
  7. Operation: prime, standby
  8. Voltage ratings: voltage, 3-phase, 1-phase, solid grounded, delta, wye
  9. Connected loads: Linear, non-linear, power factor
  10. Load operation: Motor starting methods, single step, single step with diversity, multiple steps of loading
  11. Future loads

Sizing Procedures for Generator Single or Multi-sets

The following is the sizing procedure for generator single or multi-sets:

  1. Prepare a load schedule.
  2. Enter individual load characteristics in software.
  3. Enter loads in step sequence in software.
  4. Have software calculate and select a generator set.

It is a good practice to request a verifying calculation from the preferred genset manufacturer.

Title:Electrical Design Calculations Needed For Projects – Seattle Public Utilities
Format:PDF
Size:460 KB
Pages:34
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Electrical Design Calculations Needed For Projects

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37 Comments


  1. Tewodros Habte
    Mar 15, 2024

    Where shall electrical design and calculation book softcopy.


  2. Hassan Mahmood Jamal
    Nov 12, 2023

    Greetings,

    How would i get pdf copy of electrical design and calculations book


  3. Anand prakash mishra
    Sep 24, 2023

    How can I get a pdf copy of a electrical engineering design calculation


  4. M A Islam
    Jul 30, 2023

    Hi there. How can I get a copy of the pdf file- electrical design calculation needed for project


  5. Tonderai Kavhukatema
    Jul 14, 2023

    May you send me a pdf of Electrical calculations for generator sizing power factor correction and load sizing


  6. khalid Naeim
    Jul 13, 2023

    Thanks for your useful information


  7. A.GURUSABHARI
    Mar 10, 2023

    Can you send me the Electrical Design Calculation pdf.


  8. warez ali
    Jan 27, 2023

    Good


  9. Shumbulo Shuta
    Jan 27, 2023

    thank you


  10. Chris Wu
    Jan 26, 2023

    Very nice article. Can you please send me the PDF of Electrical design calculation as well?
    Thank you very much.


  11. parisa rajaei
    Jan 26, 2023

    how I can get PDF?


  12. jameel
    Dec 11, 2022

    how can get the electrical calculations laws .. i’m electrical superviosor


  13. Okafor. Eleazer
    Dec 01, 2022

    This article is very informative.
    Please send me the PDF copy.
    Thank you.


  14. AKASH A S
    Oct 27, 2022

    please send the pdf of this topic: Electrical Design Calculations Needed For Projects


  15. Juan Carlos Guiardinu
    Oct 19, 2022

    Thank, Can you send me the PDF..


  16. William
    Sep 28, 2022

    I am beginner in Electrical engineering and would like to grow in terms of design. Please assist


  17. Arockia Das Middle Name Antony
    Sep 01, 2022

    Dear Sir,
    Thanks. This article is much useful.


    • NASSER KHADOUR
      Sep 04, 2022

      Good Day dear Arokia
      Would you please to send me this file, I am interested to get this file
      Thank you in advance
      Sincerely
      Nasser


  18. NASSER KHADOUR
    Sep 01, 2022

    Hello who may concern
    Would you please to send me this pdf (electrical design calculations needed for projects)
    I am interested to get this articular
    Thank you in advance
    Best regards
    Nasser


  19. EDEDEH MARSHALL
    Jul 11, 2022

    I AM INTERESTED IN ELECTRICAL DESIGN CALCULATIONS , PLS KEEP ME UPDATED
    thanks for the good job.


    • THOMAS MATHENDA
      Mar 09, 2023

      I’m interested in electrical design calculation on AC, and DC, and Solar system


  20. oyoo francisco stephen
    Jun 24, 2022

    am interested


  21. moradi
    Feb 02, 2022

    thats good


  22. moradi
    Jan 30, 2022

    this training have very helpfull and i am very thanks to you


  23. Ismat
    Jan 26, 2022

    thank you very much


  24. peter owu
    Jan 16, 2022

    I am very much interested in the electrical design calculations


  25. Sintayehu
    Jul 12, 2021

    thanks


  26. Ahmed
    Jul 12, 2021

    THANK YOU
    Really a good reference to review or check .. in need.


  27. Shaikh Omer Ahmed
    Jul 11, 2021

    Thanks


  28. Luis Marcelo Urrutia Serrano
    Jul 11, 2021

    Gracias. si esta buenissimo


  29. NAGENDRA MATHUR
    May 06, 2021

    Thanks ! Great Help in our day to day work
    Regards


  30. PEDRO C. RIVAS
    May 05, 2021

    Muchas gracias por tan valiosa infomacion me gustaria que me ayuden con el calculos de tendidos de lineas y tablero de distribucion para 500KVA MUCHAS GRACIAS.. Atte. PEDRO


  31. Abdullahi ismail isah
    Apr 03, 2021

    Thanks


  32. Gizat teshager
    Nov 24, 2020

    I wante to share your fundametal knowlage of eletrical design


    • TWAGIRIMANA AUGUSTIN
      Dec 07, 2020

      THANK YOU VERY MUCH, HELP ME ABOUT EXAMPLE ELECTRICAL DESIGN CALCULATIONS.YOU CAN USE MY EMAIL ADDRESS: [email protected]


  33. Edgar Esparragoza
    Jul 07, 2020

    I suggest making the audio of all your excellent articles, it permits for no English spoken to familiarized with the electrical sound and vocabulary. Thanks for the excellent work


  34. Abdalrahman
    Jun 07, 2020

    I think Good subject

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