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  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

    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...
  4. 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...
  5. 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...
  6. 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...
  7. 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...
  8. 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...
  9. ctpt

    Inrush current for two transfomer in series

    There is a system where two transformers are connected in series. There is an existing transformer of 150 kVA (480V/4.16kV) in an offshore platform. This transformer feeds a new platform at 4.16kV through subsea cable and connects to a new transformer of 200kVA ,4.16kV/480V. (I have no idea why...
  10. ctpt

    IEC-Armour as grounding conductor?

    Hi everybody, My questions are for experts in the IEC world. I understand that as per NEC, a separate grounding conductor is run with phase conductors (as a fourth core in a three phase cable or as a separate grounding conductor) especially for grounded systems <1000V. Please correct me if I...
  11. ctpt

    IEC - armour as grounding conductor?

    Hi everybody, My questions are for experts in the IEC world. I understand that as per NEC, a separate grounding conductor is run with phase conductors (as a fourth core in a three phase cable or as a separate grounding conductor) especially for grounded systems <1000V. Please correct me if I...
  12. ctpt

    Differential CT grounding

    Hi everybody! It is recommended that for a differential relay connection, the CT’s should be grounded at one end only and not at both ends. I will really appreciate if someone explains me in detail what problem is encountered if the CT’s are grounded at both ends. Is the relay going to trip...

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