Method of laying medium voltage power cables

The laying in the tunnel was introduced in the last article of The Method of Laying Medium Voltage Power Cable(?), this article is to introduce another method---Laying in Pipe.

Laying in the pipe, that is a cable laying way that when there are many cables used together, to install cables into the orderly pipeline which is safely placed underground. 

It is required that the inner diameter of the pipe is greater than or equal to 1.5 times the actual cable outer diameter, and to lay the cable under the permafrost layer.

The slope of the pipe and the direction of the work well should be greater than 0.2%, and the gaps between each pipe should be greater than 20 mm.

So that to ensure good heat dissipation. 

When installing cables, we have to make sure the entrance of the pipe is smooth, with no sharpness or sundry, to avoid the cable being scratched during installation. 

The working temperature of XLPE insulated cable is 90 ℃, when we select the pipe material, some material with good mechanical performance and heat dissipation performance shall be selected. 

Nowadays, the main pipe material is Whalen cement pipe, double-wall corrugated pipe, flame retardant PVC - C, painted plastic pipe and hot melt PE tubing, etc.

Advantages of laying in the pipe

Install cables is convenient for maintenance, and can leave room for other cables, covering area is small, and the adjustable space of the cable working well is larger, with excellent fireproof performance and strong mechanical performance. 

This cable laying way is generally used in some heavy traffic zones with many cross-links, roads, and railways, but the armored cable is not recommended to choose cable laying way. 

The shortcomings of this cable installation way are clearly, relative to the directly buried laying, its cost of cable installation is higher, and the heat dissipation performance is poorer.

And it is easy to cause XLPE insulated cable’s service life to be reduced.

Generally, XLPE insulated cable’s service life is 30 years. 

But according to statistics, cable service life will be reduced by 35% - 40% if the XLPE insulated cable was laid in the pipe improperly.

In addition, the handover head of the cable is more in such cable laying way, some hidden danger will easily occur such as leakage, small animal invasion, or tearing the cable. Also the maintenance cost is high.