Assistant engineer interview questions – 7

  • Where is the buckles relay used ?
  • Mock Interview questions -relay circuit

    In power tranformer and voltage above 750KVA

    Mock Interview questions

  • How to differentiate the 220 kv and 110 kv tower with out any specification ?
  • Calculate the number disk in the insulator .Each disk can handle the 11kv
    Number of insulator calculation for example 220 KV line .

    Number of insulator =120/(11*root2)+1

    so the Number of insulator :10

    Here root2 for the insulation depends on the peak voltage
    +1 for the more protection

    Lighting surge voltage,switching surge voltage

    lighting surge voltage:

    when the electrical equipment like fan ,tv etc are on off . Over voltage transient surge can occur in the AC power lines .Near by any lightening strike on the transmission line .Nearby lightning strikes can also generate transient surges in AC .

    switching surge voltage:

    when the sudden interruption in any circuit surges will produce .Switching surge is sudden hike in voltage level because of switching.When switching is done suddenly, there is increase in voltage for some seconds.You can see when heater is switched off, voltage surge occurs and there is change in brightness of bulb for second.

    Application of zig-zag connection in the transformer
      Harmonic voltages suppression
      Provides low impedance to zero sequence currents
      Less cost compared to Scott transformer
      It provides perfect isolation between ground and component
    full form of EHV,HVDC ?

    EHV: Extra High Voltage transmission line .It will carries 345kv – 500kv
    HVDC;High Voltage Direct current transmission line

    What is IDMT relay

    Inverse definite minimum time rely .IDMT relay is operating inverse to the current carrying by it.its minimum time relay.

    what is the need of Busbar protection

    Minimising damage at the fault location
    Maintaining power system stability
    localising isolation to avoid wide spread disruption

    Performance required for the protection relays ?
      fault clearance performance
    Disadvantage of HVDC
      power faults
      radio noise
      difficult grounding


    Hi, Myself Tony George. An Electrical Engineer by Education, a Software Developer by Profession and an Education Blogger by Passion. In the past, I had been working as an Engineer in KSEB. The knowledge that I have acquired I would like to share here with you. I will be happy if these articles can give you a way to your career growth. Feel free to contact me.

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