Edw1n (Electrical)(OP)5 Sep 24 07:23
"..Need some help on the above 'ARE CABLE CLEATS NECESSARY FOR BURIED CABLES IN TREFOIL FORMATION' . Any reference materials please".
I have the following opinion for your consideration.
1. The main purpose of the cable cleats are to hold the cable on the tray being displaced when subjected to very large dynamic force during short-circuit, especially the initial asymmetrical pecks. The cables can be pulled apart and subjected to mechanic damage etc.
2. When the cables are Buried, the problem as above 1 does NOT exist. Therefore cable cleats are not required.
Che Kuan Yau (Singapore)

I agreed with Che.

Once in operation cleats should not be required.
However, a lifetime of field experience has shown that in some instances cleats may be required to ensure that the cables are in proper trefoil configuration and remain in trefoil configuration until the cables are covered with whatever fill is used.
The definitive answer?
It depends. Your call depending on site conditions.

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Ohm's law
Not just a good idea;
It's the LAW!

'..However, a lifetime of field experience has shown that in some instances cleats may be required to ensure that the cables are in proper trefoil configuration and remain in trefoil configuration until the cables are covered with whatever fill is used'.
I have the following opinion.
1. Cable cleats are of very heavy mechanically strong design including usually anchored down on a fixed position. High cost ! , but it is mandatary when cables are on cable tray/ladder in free air.
2. To ensure that the cables are in proper trefoil..., needs very simple non-magnetic material or even plastic cable tie, to hold them together during cable laying. These are relatively simple very low mechanical strength and are very low cost. They serve NO purposes after cables are buried. Therefore, Cable cleats are NOT required.
3. Cable cleats and cable-tie are of entirely different mechanical strength/design and cost. They serve different purposes.
Che Kuan Yau (Singapore)