Metal sheathed cable designed on the basis of torque balance and design method thereof
A metal sheathed cable includes an optical unit and a control unit helically twisted together, a grounding wire unit distributed in the gaps between the optical unit and the control unit to form an inner layer cable core, a filler watertightly filled into gaps among the optical unit, the control unit and the grounding wire unit, and a taped covering arranged outside the inner layer cable core; a power unit and a filling core helically twisted around the inner layer cable core, the grounding wire unit distributed in the gap between the power unit and the filling core, the filler watertightly filled into gaps among the power unit, the grounding wire unit and the filling core, and the taped covering arranged outside the outer layer cable core; an inner protective layer wrapped outside the outer layer core, and a sheathing layer twisted outside the inner protective layer.
1. A metal sheathed cable designed on the basis of torque balance, comprising: an optical unit, a control unit, a power unit, a grounding wire unit, a filling core, a taped covering layer, a watertight filler, an inner protective layer and a sheathing layer, wherein the optical unit and the control unit are helically twisted together, the grounding wire unit are distributed in gaps between the optical unit and the control unit to form an inner layer cable core, the filler is watertightly filled into the gap among the optical unit, the control unit and the grounding wire unit of the inner layer cable core, and a taped covering is arranged outside the inner layer cable core; the power unit and the filling core are helically twisted around the inner layer cable core, the grounding wire unit are distributed in the gap between the power unit and the filling core to form an outer layer cable core,
the filler is watertightly filled into the gaps among the power unit, the grounding wire unit and the filling core of the outer layer cable core, and a taped covering is arranged outside the outer layer cable core; an inner protective layer is wrapped outside the outer layer core, and a sheathing layers is twisted outside the inner protective layer, the sheathing layer ( 9 ) adopts the design method of torque balance, and
wherein the design method of torque balance for the metal sheathed cable is as follows:
T
=
P
*
D
2
sin
θ
=
P
W
E
=
W
A
ɛ
P
=
E
*
A
*
ɛ
*
sin
θ
T
=
E
*
A
*
ɛ
*
D
*
sin
θ
2
∑
T
=
N
*
E
*
A
*
ɛ
*
D
*
sin
θ
2
R
T
=
∑
T
o
∑
T
i
=
N
o
*
E
0
*
A
0
*
ɛ
0
*
D
0
*
sin
θ
0
N
i
*
E
i
*
A
i
*
ɛ
i
*
D
i
*
sin
θ
i
E of the inner steel wire is the same as ε of the outer steel wire, then
R
T
=
N
o
*
A
0
*
D
o
*
sin
θ
0
N
i
*
A
i
*
D
i
*
sin
θ
i
A
=
π
4
d
2
R
T
=
N
o
*
d
o
2
*
D
o
*
sin
θ
0
N
i
*
d
i
2
*
D
i
*
sin
θ
i
in which, A—area of the single steel wire;
d—diameter of the steel wire;
D—pitch diameter of the sheathing layer;
E—elastic modulus of the steel wire;
N—numbers of the single steel wire;
P—circumferential force of the steel wire;
RT—torque coefficient;
T—torque;
W—tensile strength of the steel wire;
θ—stranding angle of the steel wire;
ε—strain of the steel wire;
o—outer steel;
i—inner steel.