Triplett Mitigator Loop Coil – 3232 - Manual (Page 22)

Unfortunately, the earth ground also creates a path for the Ground Return Currents to flow through.
What if current flow could be confined to the neutral wire? If this were possible, a canceling magnetic
field would be generated by the neutral and the induced noise in the telephone line should drop.
How can this be accomplished? Well, the obvious way is to remove ALL of the earth grounds from the
neutral wire. This would force the current to flow in the neutral wire. It would also present a serious
safety hazard.
However, the hazard could be minimized by removing just SOME of the earth grounds. By choosing the
grounds where most of the harmonic currents are flowing into the earth and modifying the path of these
currents so that they flow in the neutral wire, a magnetic canceling effect can be achieved that will result
in reduction of the Power Influence.
Since this technique compromises the safety of the power lines, the fewest number of disconnected
earth grounds is desirable. This means that the semi-floating method is really only usable in situations
where the Power Exposure is relatively short. Figure 10 shows an example where semi-floating may be
of some help.
Figure 10
Removing the earth ground at the capacitor has been found to be effective in providing the desired
noise reduction in some cases. But, often, the harmonic current simply flows to the next ground rod
and completes its circuit to ground. In such a situation, several grounds may need to be removed. It
must be understood that current flow in the neutral and earth ground, together, make up the total
unbalanced load current and harmonic current that must flow back to the substation. This total amount
of current divides between the neutral and the earth, the ratio depending upon a variety of conditions
(mostly, neutral resistance versus earth resistance).
If a large amount of the total current is flowing in the earth, and the bulk of that current flow is coming
through the ground rod connection at a capacitor bank, removing the single ground rod connection at
the bank may produce a significant reduction in the total Ground Return Current (which means an
increase in the neutral current and magnetic canceling field) and reduce telephone noise accordingly.
The technique of lifting (removing) the ground connection is very useful, but in some areas of the coun-
try, it is not permitted, or if it is permitted, it is done reluctantly by the power company. The actual
procedure itself is quite simple. Just remove the earth ground connection at the capacitor bank, i.e.
disconnect the “vertical” below the neutral wire. The neutral remains connected to the capacitor bank.
Although the danger of injurious shock is significantly less with a semi-floated capacitor bank, and
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