Cable experts guidence please ......... 1

[elecsun]

One of the cable manufacturers catalogue specification says 3C,Cu?XLPE/SC/Cu-tape screen/SWA/PVC rated 18/30kV(36kV) manufactured as per IEC-60502.Can i use this cable for 34.5kV rated system. What does their specified 18/30kV rating means? What does the above IEC standard says? Can some experts brief me in details?

 

[rbulsara]

It should mean
18 kV - Line to ground
30kV - Line to line..

So essentially its suitable grounded, 4-wire 30kV Y system.
Not suitable for say ungrounded or corner groudned 30kV delta system where during a fault full line-line voltage is impressed between ground and the line.

I don't know what exactly IEC-60502 reads...

 

[rbulsara]

If your system is grounded Y and impedance groudned, you still can't (or should not) use 18/30kV cable or 100% insulation rated cables.

If your system is solidly grounded, you may consider a cable with 133% insulation (which this cable won't be otherwise it won't say 18/30kV). Check with mfr. There would be a cable which says just 36 kV or 133% insulation.

I personally won't use a cable whose published rating is 30kV on a 34.5 kv system. I hate making border line decisions on such important and medium/high voltage system that deserve respect. You obviously are doing right thing by asking questions here, but the cable mfr.'s opinion should be very important.

 

[RajT]

34.5kV is not a standard system voltage in Europe, though common in some middle east countries and china.The nearest standard voltage to this in Europe is 33kV and therfore the cable supplier will normally only state the value of 33kV in their standard supply catg detail.
Some will however supply cable rated at 35kV ( and stamped accordingly) to IEC . This they will do so by increasing the insulation thickness to suit.
You should try following suppliers
General cable
Pirelli
Riyadh cables
Saudi cables

 

[TMD]

I'm not an expert, elecsun, but I'll give you some info.

The first bit describes the construction:
3C = 3 conductors
Cu = copper conductor
? = not sure, but it should be a semi-conducting layer
XLPE = crosslinked polyethylene
SC = semi-conducting screen
Cu-tape screen = copper tape screen ;-|
SWA = steel wire armour
PVC = polyvinyl chloride overall jacket

10/30(36) kV = 10 kV phase to ground, 30 kV phase to phase, 36 kV maximum system phase to phase.

For use in a 34.5 kV system, I can't say for sure, but I suspect 'no' because the cable is rated at only 30 kV l-l.

The IEC standard is lengthy. You can buy it at

http://www.iec.ch.

 

[RRaghunath]

Are you sure your system is rated at 34.5kV. It could be 33kV rated system with 34.5kV as no-load voltage and 36kV highest system voltage. This is popular in India and came from British practice.
Appropriate cable for the system would be one rated for 33kV with highest system voltage of 36kV.

Hope the above is useful.

 

[benlanz]

elesun,

This advice does not directly relate to your question but you might find it useful. Although tape shielded cable has been a standard for a long time there is something you should know about it.

If you go with tape shielded cable you will limit the types of tests you will be able to perform in the future. 10 years from installation the tapes will more than like corrode at the overlaps. This will prevent you from using TDR (radar,) to measure the length and locate joints, arc-reflection fault location equipment, should you have a fault, and the latest in cable diagnostics like PD measurements for repeating the factor baseline test.

Of course if you are 100% sure that your installers will do a perfect job there isn't any reason to be concerned, but if you are in the business of reliability you may want to consider my advice for the long term.

-cheers

 

[sdlloyd]

Elecsun,

You can use IEC60502 but it's a bit of a blunt instrument, it is a document written by manufacturers and users from around the world and thus in trying to cover such a diverse range ends up as the lowest common denominator of them all.

The specification does not, for instance, describe the cable build but rather states what tests are required for any functionallity you require. If you use IEC60502 without care you could end up with a cable suitable for use, say, in a tunnel when you actually want one suitable for buriel in wet saline soil. In oredr to avoid getting a perfectly good cable that is useless for the application you need to know what you want the cable to look like and what you want it to do in the installed environment, before you identify specification requirements.

You are probably going to be better off using a national specification, some of these have build requirements. Can I ask in which country the cable is to be installed and the environment you want the cable installed within? I may be able to give you a "better" specification.

Hope this helps.

http://www.cableconsulting.net

 

[gcameron]

You should not use a 18/30 kV cable with maximum Line voltage of 36kV on your 34.5kV system. The 34.5 kV system is popular in the US and use to some extent in Canada. You can definetly get 34.5kV rated cable in the US and Canada, you can check one of the following manufacturers:
1. Nexans
2. Pirelli
You should also note that the maximum Line voltage expected on a 34.5 kV system is 38kV which means that if you should use the above specified 18/30 kV cable on your 34.5kV system there is a possibility that it will be exposed to higher voltage than it was designed for.

Hope this helps.

Greig