Methods For Cable Laying

→ British Standard 7671.

Mr Bar Man,

Thanks

Above ground or overhead tray/channel runs are normal but practical limitation is that these usually obstruct.

One method extensively used near sea shore is to use underground ducts (PVC pipes) terminating in manholes, usual water sealing mothods are effective.

Local electrical standards and regulations applicable to your site are a good place to start. It is fairly common to place cabling in ducting (or similar tunnels) with access points above ground, rather than direct bury (requiring civil works if cables need to be accessed), it is also fairly common to cable tray cabling above ground for access or other benefits, but again it depends on what the relevant local electrical standards and regulations dictate (as well as the site standards, which can be an issue).

If flooding or seepage are an issue then there are ways around reducing and/or preventing it or its effects, but it really depends on the site, the trenches and their construction/maintenance, etc.

British unstandard 7622

I can see your problem. But generalizing it and saying that it should be mostly laid above ground is not correct. Both systems of cable laying have their merits and demerits. It is upto an engineer to adopt the most suitable method of cable laying. For example, in your case the overhead cable is quite suitable. It means laying cables on structural towers of the height of 6M or so atop which heavy duty prefabrcated/ site fabricated trays in tier formation have been welded. In my job I use both types of cable laying based on site condition and techno-economically feasibility. This is probably the best method for your site but may be costly. You are the best judge of the situation.

BB Raina

You did not mention the type of cable whether steel armoured,pvc,xlpe etc.If water seeps into trench it might increase the current rating of the pvc/xlpe cable by lowering its temperature.You should consult the manufacturer.If armoured corrosion will take place.Another weak point is joints.