Thanks for the replies.
If I should start over I would use a busbar system, but now I am stuck with cables.
I am on an IEC system and might need 8 cables depending on parameters used.
My basic problem is the current sharing.
I have seen more installations where the cables are in flat formation...
Hi Engineers
I have a 11/0.4kV 2500kVA trafo where I need 7 parallel single core cables to carry the current.
Ideal installation is 7 bunches of trefoil cables of equal length, installation conditions etc.
But the distance to LV swbd is only 5m and the phase sequence is opposite, so this...
Hi ScottyUK
I am in the early phase of a platform design and is on the limit of the 76 MVA that is a result of 11 kV and 4000 A. And when the project develops the load normally increases.
I would like to keep 11 kV and connect the generators directly to the main SWBD and I also would like to...
Hi-
I am looking for a switchboard produced after IEC62271-200 for an 50Hz - 11kV offshore installation.
General limit for most vendors seem to be 4000A nominal and 50/125kA short-circuit.
Does anyone know a vendor with higher values on one or both parameters which has a reference list for...
Hi all,
I have an offshore installation with seven 50Hz generators (3 to 7MW) that can run in parallel on a 6kV distribution system. They are all grounded by NER. (8,2 to 17,3 ohm)
The original installed generators has a winding pitch that produces 3rd harmonic and the new installed generator...
The IEC61892 series apply for offshore oil&gas installations and IEC61892-2 §11 gives the lighting requirements. The series does not give secial rules for normally unmanned installations and praxis in the Danish North-sea is to have general service light.
Best regards
Preben
Hi
According to IEC60079-14 §6.3 all exposed and extraneous conductive parts shall be connected to the equipotential bonding system which is normally the steel structure.
It is however not required to use seperate conductors if the parts are firmly secured and in conductive contact whith the...
Hi ScottyUK
As you predicted I haven't found any permissions in IEC / EN standards (untill now :) )
I have however found Offshore S
tandard DNV-OS-D201 Electrical installations which in sec.2 §202 item i) states:
When a switchboard has two incoming feeders, necessary interlocks shall be...
In the offshore sector there is tradition to supply 400V sub switchboards by two transformers each able to carry the full load. Often a "2 of 3" scheme is selected where either the bus coupler or one of the feeders are normally open (NO) which will allow lower rating of the switchboard.
If the...
Sibeen -
I agree with you that the fault is unlikely, but I find it strange that the issue is not addressed by vendors or in literature.
In my case i have an offshore installation where discrimination is a damand in safety critical systems, and protection against indirect contact is always...
Hi YuriB
If the UPS is 200kVA and a SC is made at the end of a 50m, 2,5mm2 cable the voltage will be nominal on the UPS distribution panel!
Preben Jakobsen
When calculating minimum SC value on the output side of a UPS I don't think we can use the normal IEC60909 approach.
Inverter current will be limited:
When bypass is not available the inverter alone shall supply the SC.
If SC occurs close to the UPS the impedance in the loop is low, and the...
Thanks for the posts.
My relay has an instant trip function but also a time dependant function which i would like to test at different points.
I have found a page www.relaytech.com/symcomp_calculator.htm which can do the calculations, but a spreadsheet for quick calculations on site would be...
Hi
Does anyone know where to find a simple spreadsheet that can calculate negative sequence current from a set of 3phase currents?
I am preparing a test of a Siprotec 7UM62 with a Omicron CMC256 and Siemens doesent specify how to test the function.
If I e.g. injects 1.2pu on two phases and...
