Plotting a three-core cable

In this notebook we make a three-dimensional plot of a section of power cable. There is an outer sheath, which we represent as a wireframe plot. Inside, there are three separate cores, called earth, neutral and line, which twist around each other. The neutral core is blue, the line core is brown, and the earth core has yellow and green stripes.

import numpy as np
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt

%matplotlib widget

def show_cable():
    w = 5
    R = 2
    r = 1
    s = np.sqrt(3)/2 * r
    u, v = np.meshgrid(np.linspace(0, 1, 100), np.linspace(0, 1, 100))
    ua = 2 * np.pi * u
    va = 2 * np.pi * v
    x = 10 * u - 5
    y_sheath   = R * np.cos(va) # edge of the sheath
    z_sheath   = R * np.sin(va) # edge of the sheath
    y0_earth   = r * np.cos(ua)              # centre of the earth core
    z0_earth   = r * np.sin(ua)              # centre of the earth core
    y0_neutral = r * np.cos(ua + 2*np.pi/3)  # centre of the neutral core
    z0_neutral = r * np.sin(ua + 2*np.pi/3)  # centre of the neutral core
    y0_line    = r * np.cos(ua + 4*np.pi/3)  # centre of the line core
    z0_line    = r * np.sin(ua + 4*np.pi/3)  # centre of the line core
    y1_earth   = y0_earth   + s * np.cos(4*ua+va/4)            # first green section of edge of the earth core
    z1_earth   = z0_earth   + s * np.sin(4*ua+va/4)            # first green section of edge of the earth core
    y2_earth   = y0_earth   + s * np.cos(4*ua+va/4+  np.pi/2)  # first yellow section of edge of the earth core
    z2_earth   = z0_earth   + s * np.sin(4*ua+va/4+  np.pi/2)  # first yellow section of edge of the earth core
    y3_earth   = y0_earth   + s * np.cos(4*ua+va/4+  np.pi)    # second green section of edge of the earth core
    z3_earth   = z0_earth   + s * np.sin(4*ua+va/4+  np.pi)    # second green section of edge of the earth core
    y4_earth   = y0_earth   + s * np.cos(4*ua+va/4+3*np.pi/2)  # second yellow section of edge of the earth core
    z4_earth   = z0_earth   + s * np.sin(4*ua+va/4+3*np.pi/2)  # second yellow section of edge of the earth core
    y1_neutral = y0_neutral + s * np.cos(va)                   # edge of the neutral core
    z1_neutral = z0_neutral + s * np.sin(va)                   # edge of the neutral core
    y1_line    = y0_line    + s * np.cos(va)                   # edge of the line core
    z1_line    = z0_line    + s * np.sin(va)                   # edge of the line core

    fig = plt.figure()
    ax = fig.add_subplot(projection='3d')
    ax.axis('equal')
    ax.axis('off')
    ax.set_xlim(-w, w)
    ax.set_ylim(-w, w)
    ax.set_zlim(-w, w)
    ax.plot_wireframe(x, y_sheath, z_sheath,   color='#888888', rstride=5, cstride=5, alpha=0.5)
    ax.plot_surface(x, y1_earth,   z1_earth,   color='#00ff00', rstride=5, cstride=5, alpha = 1)
    ax.plot_surface(x, y2_earth,   z2_earth,   color='#ffff00', rstride=5, cstride=5, alpha = 1)
    ax.plot_surface(x, y3_earth,   z3_earth,   color='#00ff00', rstride=5, cstride=5, alpha = 1)
    ax.plot_surface(x, y4_earth,   z4_earth,   color='#ffff00', rstride=5, cstride=5, alpha = 1)
    ax.plot_surface(x, y1_neutral, z1_neutral, color='#0000ff', rstride=5, cstride=5, alpha = 1)
    ax.plot_surface(x, y1_line,    z1_line,    color='#964b00', rstride=5, cstride=5, alpha = 1)

show_cable()

Figure