High volatge cable selection 1

[makbhure]

Can anyone guide me for selection of cables for HV transformer and motors.AS per catalogues there are two types of cables earthed and unearthed where to use which and what is the criteria for that.
Can anyone guide me or where in I should look for it.
Is the calculation similar to the low volatge or anychange
Thanks in advance

 

[busbar]

Could you please follow up with circuit voltage, system-grounding method and anticipated cable size?

Does your query involve shielded [screened?] versus non-shielded [unscreened] cables?

 

[gordonl]

In Canada (and the US I beleive) there are three grades of cable used with low resistance grounded systems as we call them.

100% insulation - ground faults clear within 1 minute
133% insulation - ground faults clear within 60 minutes
173% insulation - ground faults can persist indefinitely

An unearthed system would presumably use 173% because ground faults usually don't automatically trip.

 

[cuky2000]

To be able to help you, please be more specific with your question describing the application, system parameters, major apparatus, rating and type of the load.

If you are not sure how to start, probably a good advise to hire an experience-consulting engineer and work together designing the system to operate safe, economical and efficient manner. This is a great way to learn.

 

[makbhure]

Thnaks busbar
The system voltage is 11KV and anticipated cable size is 50 mm2.

 

[sunilji]

The cross section of HV cables are usually selected on the basis of short circuit current withstand capacity in addition to current carrying capacity. This data is usually given by cable manufacturers. After calculating the prospective short circuit current, select the appropriate cable from the chart. Cross check the estimated voltage drop for the given length and ensure it is within limit.
If you are using :
a) 3 core 11kV armoured cable and
b) jointing kits to terminate the cable and
c) it is possible to earth the outer sheath,
then you may select Earthed cable which is generally cheaper

Usually when you are using 11kV cable for giving connection to a step-down transformer, motors, metering equipment and switchgear, Earthed cable is used.
When you are using HV cable for joining two sections of overhead 3 wire, 11 kV feeder you may use Un-Earthed cable.

 

[RRaghunath]

IEC 60502 also has similar classification like IEEE. There the cables are known as Category A, B and C for 1min, 1hr and indefinite withstand under single earth fault condition.