IEC cable voltage ratings

[TMD]

Can anyone tell me, or direct me to info on, IEC cable voltage ratings? I've seen IEC cables rated 6/10(12) kV. What do these numbers refer to? And how does it relate to the North American 100%/133% ratings? The first number*SQRT(3) equals the second. But what is the number in ()? And how does this apply to single core cables?

 

[jbartos]

Suggestion: IEC cable standards are available at:

http://www.iec.ch

 

[jbartos]

Suggestion: Visit

http://www.ewh.ieee.org/soc/pes/icc/subcommittees/subcom_a/wg_a14/wg2_14_1998.htm

etc. for more info

 

[sdlloyd]

6/10(12)kV

6kV = phase to earth voltage
10kV = Phase to phase (line voltage)
12kV = Um maximum line voltage

This notation applies to single core or 3 core cables.

http://www.cableconsulting.net

 

[cuky2000]

Q1] What do these numbers refer to?
A1] Standard cable nomenclature based on IEC Std 183 used to designate cable voltage rating as follow:
Uo/U (Um)

^{Were
Uo = rated rms power frequency voltage, core to screen or sheath ~(VLN)
U = rated rms power frequency voltage, core to core. (VLL)
Um = max. rms power frequency voltage, core to core. (max VLL ~1.05 to 1.10 VLL)}


Q2] How does it relate to the North American 100%/133% ratings?

A2] Even though there is not a through equivalent IEC also provides 3 categories similar to 100% 133% and 173% as follow:
-100% time to remove fault < 1 min ~ CATEGORY A: Phase conductor in contact with ground fault is automatically disconnected from the system.
-133% time to remove fault < 1 hr ~CATEGORY B: Under fault condition, a cable will operate for short time (<8hrs) with one phase grounded without exceeding 125 hr during 12 months period.
-173% continuous time ~ CATEGORY C: System that does not fall into category A and B.

 

[TMD]

sdlloyd:

This is clear to me in terms of multicore cables. I still struggle with the theory of how a l-l voltage can be specified for a single core cable, particularly a screened cable.

I don't have IEC 183, maybe a clue to the next question is there. Is there a method to convert a &quot;North American&quot; specified cable (15 kV) to an IEC equivalent? Effectively, the l-gnd rating is 15 kV.

Thank you all for your responses.

 

[sdlloyd]

At high voltages, phase to phase line voltages are quoted for single core cables as at these voltages the cables are almost always used in three phase systems (one exception being railways).

A 345kV cable is the accepted way of describing a screened cable working on a 345kV LINE voltage system. A single phase system at this voltage just doesn't exist. (Unless you know otherwise!).

IEC is an international standard which gives voltage ranges in order to group together cables of similar constructions/purpose.

If 15kV is your conductor to ground voltage then the phase to phase (line voltage) is 15kV x Root3 = 26kV.

If you were to buy from a European manufacturer then you need a 30kV cable, probably to IEC 60502 or similar. (By the way, IEC 183 has been renumbered IEC 60183.)

IEC use sq.mm as opposed to kcmil so make sure you convert conductor sizes and dimensions when looking at IEC cables.

You can find the standard conductor sizes and a dc resistance calculator at:

http://www.cableconsulting.net/design/design_dc_resistance.htm

Hope this helps.

http://www.cableconsulting.net