Electrical Thumb Rules You MUST Follow (Part 2)

Electrical Thumb Rules You MUST Follow // PART 2 (on photo: Osprey Lunch Among The Electrical Wires! by Kathleen Jackson via Flickr)


Continued from first part: Electrical Thumb Rules You MUST Follow (Part 1)


Useful Electrical Equations

  • For Sinusoidal Current: Form Factor = RMS Value/Average Value = 1.11
  • For Sinusoidal Current: Peak Factor = Max Value/RMS Value = 1.414
  • Average Value of Sinusoidal Current (Iav) = 0.637 x Im (Im = Max.Value)
  • RMS Value of Sinusoidal Current (Irms) = 0.707 x Im (Im = Max.Value)
  • A.C Current = D.C Current/0.636.
  • Phase Difference between Phase = 360/ No of Phase (1 Phase=230/1=360°, 2 Phase=360/2=180°)
  • Short Circuit Level of Cable in KA (Isc) =
    (
    0.094 x Cable Dia in Sq.mm) /√ Short Circuit Time (Sec)
  • Max.Cross Section Area of Earthing Strip (mm2) = √(Fault Current x Fault Current x Operating Time of Disconnected Device ) / K
    K = Material Factor, K for Cu = 159, K for Al = 105, K for steel = 58 , K for GI = 80
  • Most Economical Voltage at given Distance = 5.5 x √ ((km/1.6) + (kw/100))
  • Cable Voltage Drop (%) =
    (
    1.732 x current x (RcosǾ+jsinǾ) x 1.732 x Length (km) x 100) / (Volt(L-L) x Cable Run.
  • Spacing of Conductor in Transmission Line (mm) = 500 + 18 x (P – P Volt) + (2 x (Span in Length)/50).
  • Protection radius of Lighnting Arrestor = √h x (2D-h) + (2D+L).
    Where h= height of L.A, D-distance of equipment (20, 40, 60 Meter), L=V x t (V=1m/ms, t=Discharge Time).
  • Size of Lightning Arrestor = 1.5x Phase to Earth Voltage or 1.5 x (System Voltage/1.732).
  • Maximum Voltage of the System = 1.1xRated Voltage (Ex. 66KV = 1.1 × 66 = 72.6KV)
  • Load FactorAverage Power/Peak Power
  • If Load Factor is 1 or 100% = This is best situation for System and Consumer both.
  • If Load Factor is Low (0 or 25%) = you are paying maximum amount of KWH consumption. Load Factor may be increased by switching or use of your Electrical Application.
  • Demand Factor = Maximum Demand / Total Connected Load (Demand Factor <1)
  • Demand factor should be applied for Group Load
  • Diversity Factor =
    Sum of Maximum Power Demand / Maximum Demand (Demand Factor >1)
    Diversity factor should be consider for individual Load
  • Plant Factor (Plant Capacity) = Average Load / Capacity of Plant
  • Fusing Factor = Minimum Fusing Current / Current Rating (Fusing Factor>1).
  • Voltage Variation (1 to 1.5%) = ((Average Voltage – Min Voltage) x 100)/Average Voltage
    Ex: 462V, 463V, 455V, Voltage Variation= ((460 – 455)  x 100)/455 = 1.1%.
  • Current Variation (10%) = ((Average Current – Min Current) x 100)/Average Current
    Ex: 30A,35A,30A, Current Variation = ((35-31.7) x 100)/31.7 = 10.4%
  • Fault Level at TC Secondary
    = TC (VA) x 100 / Transformer Secondary (V) x Impedance (%)
  • Motor Full Load Current = Kw /1.732 x KV x P.F x Efficiency

author-pic

jiguparmar - Jignesh Parmar has completed his B.E(Electrical) from Gujarat University. He is member of Institution of Engineers (MIE),India. Membership No:M-1473586.He has more than 12 years experience in Transmission -Distribution-Electrical Energy theft detection-Electrical Maintenance-Electrical Projects (Planning-Designing-Technical Review-coordination -Execution). He is Presently associate with one of the leading business group as a Assistant Manager at Ahmedabad,India. He has published numbers of Technical Articles in "Electrical Mirror", "Electrical India", "Lighting India", "Industrial Electrix"(Australian Power Publications) Magazines. He is Freelancer Programmer of Advance Excel and design useful Excel base Electrical Programs as per IS, NEC, IEC,IEEE codes. He is Technical Blogger and Familiar with English, Hindi, Gujarati, French languages. He wants to Share his experience & Knowledge and help technical enthusiasts to find suitable solutions and updating themselves on various Engineering Topics.



5 Comments


  1. Rajan.K
    Jul 28, 2014

    The thumb rules are really great. thanks a lot for providing such information in a capsule


  2. NITIN
    May 30, 2014

    Size of Lightning Arrestor = 1.5x Phase to Earth Voltage or 1.5 x (System Voltage/1.732)
    MEANS WHAT SIZE OF THAT ARRESTER ???


  3. PARAG NIKUMBH
    Dec 16, 2013

    will reply once sure


  4. aakifnouman
    Sep 02, 2013

    A.C Current = D.C Current/0.636

    what is 0.636??


  5. sumitfloyd
    Sep 02, 2013

    A.C Current = D.C Current/0.636.
    Please clarify this relation on how do you get it?

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