Calculation of IDMT Over current & Earth Fault Relay Setting:

 IDMT Over current & Earth Fault Relay Setting:

  • Calculate IDMT Over Current Relay Setting (50/51)
  • Calculate IDMT Over Current Relay Pick up setting.
  • Calculate IDMT Over Current Relay PSM.
  • Calculate IDMT Over Current Relay Time setting.
  • Calculate Actual Operating time according to Various IES Curve.
  • Calculate Low current Setting(I>).
  • Calculate High Current Setting(I>>)
  • Calculate Actual Operating Time of Relay(t>)
  • Calculate Actual Operating Time of Relay(t>>)
  • Calculate IDMT Earth Fault Relay Setting (50N/51N) 
  •  Calculate IDMT Earth Fault Relay Pick up setting.
  • Calculate IDMT Earth Fault Relay PSM
  • Calculate IDMT Earth Fault Relay Time setting
  • Calculate Actual Operating time according to Various IES Curve.
  • Calculate Low current Setting(Ie>)
  • Calculate High Current Setting(Ie>>)
  •  Calculate Actual Operating Time of Relay(te>)
  •  Calculate Actual Operating Time of Relay(te>>)

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About Jignesh.Parmar
Jignesh Parmar has completed M.Tech (Power System Control), B.E(Electrical). He is member of Institution of Engineers (MIE) and CEng,India. Membership No:M-1473586.He has more than 16 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 Deputy Manager at Ahmedabad,India. He has published numbers of Technical Articles in “Electrical Mirror”, “Electrical India”, “Lighting India”,”Smart Energy”, “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.

26 Responses to Calculation of IDMT Over current & Earth Fault Relay Setting:


    Could u please explain selection of MCB, ELCB and cable selection for Electrical DBs?
    light, power, AC unit, single phase,three phase etc..

    • Refer Page of “Electrical Tools” of this Blog……….

      • ALI says:

        What is the settings of protection relay Micom p121 connected to 208 feeder incomer circuit breaker CT 1600/5 Transformer 2300/208v z= 6.03% 500kva. 2300v feeder supplied via oil fuse switch with 160 amps fuses. Please find me O/C & EF 208 v incomer relay settings?

      • abbas says:

        how to set for high set e/f relay for 400/1amp ct for 33kv feeder

  2. Sanjay Limbore says:

    In case of 22kv ht line, if loose or improper connection at any phase , it always show fault at LT side for Earth fault and LT breaker keeps on tripping . Observed this condition mostly when rainy seasons starts.

  3. blesson says:

    Hi Jignesh,

    You have a real good workmanship ..Aprreciate the efforts and accuracy.

    Do you have a excel sheet to do touch volatage calculation for a site.

    Also how to calculate the impedances on phase sub circuits , sub circuits earth , submains and phase..please assist me

  4. prathap says:

    hi jignesh thanks for ur wonderful work i av one request can u tel me that how to calculate impulse calculation for power transformers ,because this known only few people am also design power transformer design engineer am waiting for ur reply

  5. sami says:

    thank you very much for these useful programs

  6. Arul says:

    hello sir

    Your are awesome

    Ur dedication in Electrical field is impressive
    Thank you very much for the information on Electrical safety clearance

  7. Ashok Gupta says:

    Dear sir,
    Thanks for sharing the calculations. Can you please give me the setting calculations for 64R relay.

  8. Gaurav shah says:

    Dear sir

    we have motor of 200 kw , FLC 24 A Ht motor ABB make with we have used SPAM 140c MPR relay kindly tells us how relay setting is done.for example what value of current is set of I> I>> etc.

    Gaurav shah

  9. hardip dodiya says:

    i just want to tell u you…sir..

    you make all sense of electrical parameter to us….working and guide like god of electrical engineering….thank you so much for your support.

  10. hardip dodiya says:

    Que.1 why TR NCT ratio higher than primary side CT? might be for fast response at small fault current? nt clear.

  11. hardip dodiya says:

    Que.1 In 220/66/11 switchyard 220kv level we use Y-Y1 type vector group trafo and 66kv side as general we know Dy11 used.

    pls answer sir…

  12. tonmoy says:

    thank u so much

  13. zakeer husssain says:

    Thanks alot

  14. achyut says:

    Gud afternoon Sir.
    For elect. Designing which course will be better- to develop and calculate

  15. labh singh says:

    Short and clear calculations

  16. Arvind vaghamare says:

    sir please tell me about micom p111
    50/51/50N/50N/ micom-111L
    over current setting and earth fault protection setting

  17. ajit says:

    DEAR SIR,ction realy
    I need electrical transmission protection realy (ret650,ref 615),feeder protection relay calculation OR can you suggest me any easy reference book, we are easily understand all this things

  18. Arun kumar says:

    Dear sir,
    Thankyou for sharing the IDMT oc & ef relay calculations.

  19. hariharan says:

    Dear sir,

    I am servicing in defense sector. I recently assigned for electrical department.
    Can u pls say about working of over current & EF relays with current direction( normal & fault).

    If u refer any book or article also finr foe me.

  20. Momina Rehman says:

    Can you please explain how to do earth fault protection settings in low voltage switchgear?

  21. Vishesh Kumar says:

    We have Step-up Transformer 3.6MVA, 0.433/6.6KV, LV Delta and HV Star, Primary 4800Amp., Secondary 314Amp. What will be the CT Ratio and Burden? We should use NCT or REF CT for Earth fault Protection of Transformer.

  22. c sundarrajan says:

    Sir,iam working in power generating plant having capacity of 21MW.We are facing a problem in 11KV over head distribution(ACSR bare conductor through RCC poles around 2KM from our 11KV panel)line.If any earth fault occured in the 11KV overhead line the generator incomer tripped due to earth fault.Thanks for suggestion

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