3-Phase Power Cable
A 3-phase power cable is modelled using hshear355 type of elements. The 500 mm^2 power phases each consist of 1+6+12+18=37 copper wires, an isolation layer, a layer of 52 screening wires OD 2 mm, and finaly an isolation layer.
Outside of the 3 conductors there is a plastic sheath, a layer of steel armour and another sheath, all of them modelled by use of hshear363 elements.
One pitch length of the cable length is represented. The applied loads are
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external pressure on the cores
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tension - applied by pre-straining a help system in the cable center, element type pipe31
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bending - applied by end rotations. The help-elements are stiff in bending to ensure a fairly constant curvature.
The layers within the conductor are all modelled using hshear355 elements. One element is in this case used to represent the layer regardless of the layers beeing helical components or tubulars. If the layer is a helix layer, axisymmetric effects are obtained analytically and a moment-curvarure approach is used to calculate the bending stresses on the individual components of the layer. The moment-curvature relies on the relevant contact pressure between the layers, which are modelled and obtained using contact elements of type hcont464.
Model description
Nodes
6 different groups of nodes are defined for this model:
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The center nodes which will be referenced by the helix elements, and also applied by the help system elements
Nocoor Coordinates
1 -0.8977 0.0 0.0
41 0.8977 0.0 0.0
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The helix center nodes, that all the layers within one core will be connected to:
# x0 y0 z0 b1 b2 b3 R node xcor theta
Nocoor Polar 0.0 0.0 0.0 0.0 0.0 0.0 0.025 30001 -0.8977 -3.1416
30041 0.8977 3.1416
repeat 3 41 0.0 2.094
For users familiar with the use of hshear353 helix elements elements, this is the eqivalent of the helix nodes applied for that element.
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The nodes that will keep track of the radial deformation of each concentric layers with reference to their common center point. Each layer must have a uniqe node:
# no x y z
Nocoor Coordinates
40001 -0.8827 0.0 0.0
40080 0.8678 0.0 0.0
40081 -0.8827 0.0 0.0
40160 0.8678 0.0 0.0
40161 -0.8827 0.0 0.0
40240 0.8678 0.0 0.0
The section above defines the radial nodes required for the center wire of the three conductores. Additional groups of nodes must be defined for all the other layers of the conductor.
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Three groups for the radial nodes of outer sheaths and armour.
Conductor structural elements and contact within the conductor
The inner wire (copper0), and first layer (copper1) of copper wires of the conductors are connected as follows
# group elty material no n1 n2 n3 n4 n5 n6
Elcon copper0 hshear355 coppermat 30001 1 2 30001 30002 40001 40002
30040 40 41 30040 30041 40079 40080
30041 1 2 30042 30043 40081 40082
30080 40 41 30081 30082 40159 40160
30081 1 2 30083 30084 40161 40162
30120 40 41 30122 30123 40239 40240
Elcon copper1 hshear355 coppermat 31001 1 2 30001 30002 41001 41002
31040 40 41 30040 30041 41079 41080
31041 1 2 30042 30043 41081 41082
31080 40 41 30081 30082 41159 41160
31081 1 2 30083 30084 41161 41162
31120 40 41 30122 30123 41239 41240
The first element in each of the three conponents of both layers share the same two center nodes (n1 and n2). Further for each of the three components, the two layers belonging to the same helix share the same two helix center nodes (n3 and n4). The last radial nodes (n5 and n6) are unique for each of the layers.
To capture the contact pressure between the the core wire and the first layer a set of contact elements is required. This contact connects the outer radial node (n6) of the inner wire to the inner radial node (r5) of the layer outside.
#ELCON ELGR ELTY MATNAME ELID NOD1 NOD2 REPEATAT N NELINC NODINC]
Elcon coppercontact1 hcont464 contmat-1 50001 40002 41001
50040 40080 41079 repeat 3 40 80
The same approach is used for the remaining layers in the conductor.
Contact between conductors
Contact elements are defined between the three power phases by using the hshear455 element. Note that the gap parameter of the contint is used to control which friction effects to be include in the contact.
Contact from conductor to outer sheath layer
The contact from the three power cores to the sheath outside is modelled using hshear463 element. This is the same element which is applied for contact between a helix353 layer and concentric hshear363 or hshear364 elements.
It is noted that when this is used in combination with hshear355 as in this case, the contact forces acting will also be felt as a (distributed) pressure outside of the outer layer of the power phase component.
Relevant files
User manual for reference
Processing of files from command line
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bflex2010 -n bflex2010_04