Spacing Between132 kV Single Core Cables Laid in Cable Trench

There is no recommended spacing. As the separation distance between XLPE cables is reduced one has to apply higher de-rating factors accordingly.

The de-rating factor charts and other sizing criteria are provided free on request by the cable manufactures.

In your case the designer should have taken into account certain separation while selecting a particular size for the given loading and is liable to declare that minimum spacing requirement to the contractor and the supervisors.

Apart from Continuous Current rating/derating factor related issues, is there any safety related issues considering the level of voltage handled in this case?

Will it be possible to attend to a faulty cable of one circuit with out exposing the maintenance personnel to any safety hazard while the other circuit laid in the same trench continues to feed the BUS ? If not,what should be the safe distance between the two circuits ?

Will a brick or precast slab partition between the two circuits help? If yes,should it be provided all through the entire route or only at the location of cable joints ?

It is always a compromise between economy & safety. Best is to keep maximum possible seperation, but at what cost? So, a nominal spacing is maintained depending upon the site conditions and duly applying rating factors for the cables. I suppose the cables are insulated. So, what is the worry of having access to a live cable while working on a dead cable nearby? Isn't the cable insulated to the full voltage? Of course, a concrete seperation slab would definitely help from causing an inadvertant mechanical injury to the cable.

So, a nominal spacing is maintained depending upon the site conditions and duly applying rating factors for the cables.

Can you please give the value of recommended nominal spacing between the cables in our case ( refer the initial post at the top).

Vide Clause 6.3.3 of IS 1255 (Indian Standard Code of Installation & Maintenance of Power Cables): "Laying Cables Direct in Ground - Clearances: The desired minimum clearances are as follows:

Power Cable to Power Cable: Clearance not necesary; however, larger the clearance, better would be the current carrying capacity".

So, no clearance is mandated by the Standard. If you want to know the de-rating factors, you may refer to any cabl manufacturer's catalogue.

Thank you electricalexpert65 for your help.But ,the IS 1255 you have mentioned pertains to power cables upto and including 33kV only.Will it be applicable for 132 cables too ? Or there are other IS/Standards/Guide lines ? Can you or other experts in the forum throw some light on this ?

Hi,

Spacing between the power cables can consider depends up the current carrying calculation and type of bonding.

Hi,

Spacing will not solve the problem. IEC 60287 will give you the solution for the above said. Thermal resistivity of soil to be tested as per IEC requirment 1.2 degree m k/w.

If you achieve the same, i hope you can go upto minimum spacing 250mm to 300mm.

During the calculation following things to be considered

1. Open cut road crossing

2 If, any existing parallel cable circuits

3. Ambient temperature.

regards,

gopinath