Electric Power Generation, Transmission, and Distribution

The equipotential lines are circles in case of one conductor above the ground. The voltage difference
between the conductor and the equipotential line is constant.
From a practical point of view, the voltage difference between a point in the space and the ground is
important. This voltage difference is called space potential. Figure 19.8 shows the electric field lines and
equipotential lines for a charged conductor above ground.

19.4.1 Electric Charge Calculation

Figure 19.9shows a three-phase, horizontally arranged transmission line. The ground in this figure
is represented by the negatively charged image conductors. This means that each conductor of the line is
represented by a positively charged line and a negatively charged image conductor. The voltage difference
between the phase conductor and the corresponding image conductor is 2Vln. The electric charge on an
energized conductor is calculated by repetitive use of the voltage difference equation presented before.

E

D 1 D 2

Q

X

FIGURE 19.7 A charge generated electric field.

Electric Field

Lines

Equipotential

Lines

Conductor

Ground

FIGURE 19.8 Electric field around an energized conductor above the ground.