This example models the situation where an E-field receiver is operating
near to a 50Hz overhead power line, as in the adjacent photo. The top
wire carries 240V, the middle wire is neutral and the lower wire is earth.
This example models the situation where an E-field receiver is operating
near to a 50Hz overhead power line, as in the adjacent photo. The top
wire carries 240V, the middle wire is neutral and the lower wire is earth.
The model sets up a moveable E-field probe consisting of a single sphere
at 3m height above ground. This height is chosen because it is close to
the effective height of the actual E-field receiver.
A file pwrline.in contains
line_len = 118 ; Total length of line
line_height = 6 ; Height of top wire above ground
line_space = 0.2 ; Vertical spacing of the three wires
probe_dist = 60 ; Distance of E-field probe from power line
probe_height = 3.0 ; Height of probe sphere
electrode {
name live_wire
wire {
end1 -line_len/2, 0, line_height
end2 line_len/2, 0, line_height
wirad 5mm
tiles 500
}
}
electrode {
name neutral_wire
wire {
end1 -line_len/2, 0, line_height - line_space
end2 line_len/2, 0, line_height - line_space
wirad 5mm
tiles 500
}
}
electrode {
name earth_wire
wire {
end1 -line_len/2, 0, line_height - 2 * line_space
end2 line_len/2, 0, line_height - 2 * line_space
wirad 5mm
tiles 500
}
}
electrode {
name probe
sphere {
center 0, probe_dist, probe_height
radius 0.2
}
}
ground {
center 0, 0, 0
axis 0, 0
}
A Spice sub-circuit is generated with
lcng -o spice pwrline
A test circuit puts 240VAC on the live wire and then measures the potential of the probe sphere at 50Hz. pwrline-test.spice contains
Powerline .OPTIONS NOMOD NOPAGE .AC LIN 1 50 50 .PRINT AC V(1) .INCLUDE pwrline.spice * 240 volt AC on live wire Vin 0 200 DC 0 AC 240.0 X1 0 1 0 0 200 pwrline RB 0 1 100G .ENDThis is run with the command
ngspice -b pwrline-test.spice > pwrline-test.outA simple shell script is easily employed to repeatedly run lcng and ngspice with a range of probe distances up to 150m. The results are plotted in the graph below.
This example models a real receiver case. The antenna has an effective height of about 3m and is located 65m from the power line. The 50Hz signal at the antenna terminal is around 140mV RMS. Some of this is coming from more distant power lines.