High Voltage Cable Routing

[timm333]

Is there some IEEE standard which describes the procedures for the routing of 400 kV industrial copper cables in tray/duct/buried/conduit? I am looking for information about specifications for cable spacing, road crossings, interference, location of splicing, whether trefoil configuration and transposition is required, how often the screen should be grounded, etc. Thanks for help.

 

[Ingenieur]

400 kv distribution?
wow

 

[Julius Right]

In my opinion, most of answers you may find in National Electric Safety Code IEEE C2 Part 3.
file:///C:/Users/user/Downloads/previews-1914980_pre.pdf

 

[timm333]

It is not distribution. 400 kV is stepped down for distribution, but 400 kV line is underground (not overhead). So basically it is underground short distance transmission.

 

[Ingenieur]

just haven't seen 400 kv before
it's not a standard ANSI rating; 230, 345 then 500
sounds like very specialized work

perhaps foreign, like middle east

basic info:
http://www.nexans.com/Corporate/2013/60-500_kV_High_Voltage_full_BD2.pdf

 

[Julius Right]

See-also:
http://www.nexans.com/Corporate/2013/60-500_kV_High_Voltage_full_BD2.pdf

 

[Julius Right]

Sorry, I forgot this:
IEEE Std 575™-2014 IEEE Guide for Bonding Shields andSheaths of Single-Conductor Power Cables Rated 5 kV through 500 kV

 

[timm333]

Thanks, these all documents have good information. Should the transposition of phase-conductors and/or outer-cable-shield be done for short runs (less than 3 miles) of high voltage underground cables? Just thought to get opinion what you guys think about it.

 

[Ingenieur]

Thanks, these all documents have good information. Should the transposition of phase-conductors and/or outer-cable-shield be done for short runs (less than 3 miles) of high voltage underground cables? Just thought to get opinion what you guys think about it.

the first case study/example for 400 kv is <6 miles and shows transposition

the doc implies it is required
if the conductors are not, the ground should be

Earthing cable
In the case of special screen
connections, the earthing cable will
be placed in the conduit above the
cable trefoil, as near as possible to the
cables, in order to reduce induced
voltage on the cables.
The earthing cable will be transposed
if the cables are not.
In certain cases of areas with stray
currents, an auxiliary earthing cable
may be laid in the same way.

 

[Bugman1400]

Never heard of 400kV stepped down to distribution either. I'll bet the lowside fault current on that is through the roof!

 

[timm333]

When we don’t transpose the phase-conductors but just transpose the shield/screen of the cables, this is called cross-bonding of cables (as attached). If the cables are in conduits, we will have to discontinue the conduits to do the cross-bonding of shield/screen. How should the cables be mechanically protected at the point of cross-bonding, maybe cross-bonding should be done in something like a jointing chamber?

 

[Julius Right]

Link Boxes

Link Boxes

See-for instance:
Raychem[ Tyco Electronic Power Division] Link Boxes
http://www.elektroskandia.ee/pub/tooted/keskpinge-korgepinge/Brochure-EPP-1665-4-09-Link-Box.pdf
and:
http://www.coronabd.com/download/Raychem 132KV LinkBox.pdf

 

[Julius Right]

See also:
https://www.energinet.dk/SiteCollectionDocuments/Danske dokumenter/Om os/ETS-53-01-01 Link boxes.pdf

 

[timm333]

The IEEE-575-2014 Annex D Section D.2.1 gives the equation for the calculation of voltage-gradient induced in the cable sheath/shield (as attached). The solution to this equation would be a complex number which would be equal to the voltage-gradient in volts/meter. Can we just take the absolute value of this complex-number, and ignore the angular part. Or should the angular part of the complex-number also be part of the voltage-gradient? Thanks

 

[The Great Sarducci]

Never heard of 400kV stepped down to distribution either. I'll bet the lowside fault current on that is through the roof!

Probably one of the very few situations out there where one could transform a small metal object into an atomic mushroom cloud, haha.

 

[Julius Right]

Never heard of 400kV stepped down to distribution either. I'll bet the lowside fault current on that is through the roof!

A “deep" connection transformer of 110/1 kV for 6 MW D.C. supplied motor
was installed about 30 years ago in Europe steel plant for roughing slab rolling driving.
Now synchronous motor are employed instead of [ 110/3.1 kV].
http://www.abb.com/cawp/seitp202/2d959541fc5683f144257e4900661788.aspx

 

[Julius Right]

If you mean the absolute value of the complex Ea then this is what you need in order
to compare with what it is recommended in Annex C.