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Recent content by ctpt

  1. ctpt

    Generator High Resistance Grounding connection

    This is for an offshore installation, IEC world. There are 4 gas turbine generators (4x33%) connected to a 6.6kV switchboard. The generators are high resistance grounded (20A per generator). It is a 3 Ph, 3 wire system Now regarding the connection of the resistors to the installation structure...
  2. ctpt

    Generator High Resistance Grounding Connection

    This is for an offshore installation, IEC world. There are 4 gas turbine generators (4x33%) connected to a 6.6kV switchboard. The generators are high resistance grounded (20A per generator). It is a 3 Ph, 3 wire system Now regarding the connection of the resistors to the installation structure...
  3. ctpt

    Battery & Charger Requirements for Stand-By Generator Starting

    The battery and Charger System generally comes along with the DG set as a standard vendor design. Following is generally specified by customer: -the number of consecutive starting attempts -Input supply voltage/ frequency to the charger -any metering/ lamp requirement on the charger -cable...
  4. ctpt

    Unmanned Offshore Platform Power Supply

    Is it a Wellhead Platform?
  5. ctpt

    PE conductor in Instrument tray

    Bill, The grounding conductor is for grounding Instrument equipment (DCS, Fire & Fas Panel etc.). Actually, a single core, 70 sq.mm. cable (EPR Insulated) runs across the room. Individual grounding conductor (16 sq.mm, EPR )from each Inst. Equipment is connected to this 70 sq.mm. cable. A...
  6. ctpt

    PE conductor in Instrument tray

    Hi all, With reference to an offshore project (IEC design), please inform if it is allowed to run PE (Protective Earth)Conductor on an Instrumentation cable Tray. The electrical power system is a 415V solidly earthed. The installation is an Instrumentation Technical room where it is required to...
  7. ctpt

    One breaker for multiple motor protection?

    Does IEC allow protection of more than one motor by one common breaker? I have come across a vendor drawing for a 'Davit' where there are two motors (one for hoisting and the other for slewing, both around 1 hp). And both these motors are protected by one common breaker. Is it ok?? IEC...
  8. ctpt

    AC Single core cable armour grounding one end only???

    Hi Jerryjointer, If cables are laid in a trifoil formation (in a 3 phase system), then the induction effect should mutually get cancelled and there should be no induced voltage.
  9. ctpt

    AC Single core cable armour grounding one end only???

    I posted this few days back but received no reply in the forum. Trying my luck again.... Spec. of one of the projects I am working requires that "Armour of all single core AC power cables shall be grounded at one end only”. I understand it is to do with circulating current but can't visualize...
  10. ctpt

    Single Core cable armor grounding

    Spec. of one of the projects I am working requires that "Armour of all single core AC power cables shall be grounded at one end only”. I guess it is to do with circulating current but can't visualize real problems for power cables. The project comprises of 6kV and 400V system and both systems...
  11. ctpt

    Grounding Cable Type

    Yes, I was talking about the cable from the primary wye side neutral to ground. The 30A ground fault current value through this cable is driven by the resistor put at the secondary delta corner. One would assume that the voltage drop across the resistor during fault would keep the primary...
  12. ctpt

    Grounding Cable Type

    A 6.6kV system is fed by 6.6kV generators, the generator neutrals are ungrounded. However, the 6.6kV bus is grounded by a grounding transfomer. The grounding transformer is primary star and secondary open delta with a resistor connected at the open delta to limit the gound fault current to 30A...
  13. ctpt

    MOV breaker and conductor sizing

    HI 00123456, Yes, you are correct. I'm talking about Motor Operated Valve. I should've expnaded it earlier. A single 480V supply goes to the actuator of the valve within which there are circuits for forward-reverse operation. I was refering to the single 480V supply breaker. Thanks,
  14. ctpt

    MOV breaker and conductor sizing

    Hi 00123456, Each MOV is protected by a 40A breaker. Considering the MOV size and conductor size, is the breaker rating OK per NEC? Normally a size 12 conductor should not have more than 20A breaker but is it true for MOV application?
  15. ctpt

    MOV breaker and conductor sizing

    Hi All! I have MOVs rated at 2290VA (3ea.) and 4410VA (4ea.), all 3 phase. MOVs are fed from a 480V, 3 phase panel. The MOVs are protected by a 40A breaker (short circuit protection only) and conductor size is 3C,#12. Could you please suggest 1.if the breaker is sized correctly as per NEC. 2...
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