Triplett Mitigator Loop Coil – 3232 - Manual (Page 21)

The capacitors’ connection to the neutral and the earth ground are the culprits in this game. As already
explained, capacitors act as very good harmonic current loads. If we assume that there is a source of
harmonic current on the power line, this current will flow to the capacitor load and complete its circuit
by flowing into the neutral wire and earth ground. Since a portion of the current flows in the earth
ground, the neutral wire will not produce sufficient magnetic fields to cancel the fields of the phase
wires. The result is the radiation of excessive magnetic fields from the power lines. This is explained in
better detail in the MITIGATOR Applications Manual.
How can we prevent the flow of these harmonic currents to neutral and the earth ground? What if we
just disconnected the wye point from the neutral and earth ground? What would the consequences be?
Surprisingly, with the wye point disconnected from the neutral and earth ground, THE CAPACITORS
STILL PROVIDE POWER FACTOR CORRECTION OF THE 60HZ [50HZ] CURRENTS ON THE POWER
LINE.
Consequently, the path for the harmonic currents can be effectively interrupted, and the power com-
pany is able to maintain its 60Hz [50Hz] power factor correction.
In the ideal situation, the wire that connects the wye point to the neutral could be removed, and the wye
point would still remain at ground potential. However, in the real world, conditions are far from ideal,
and the voltage on the wye point would float around, possibly reaching several thousand volts under
certain conditions.
This is why the power company doesn’t like floating capacitors. A point which is usually thought to be
at ground potential could have hazardous voltages on it. But, as said, in some situations, this technique
results in a significant reduction in Power Influence without adding any extra devices.
Floating a capacitor bank can be effective in reducing influence problems resulting from both resonant
conditions and sink effects.
A cautionary note. This technique should only be attempted by knowledgeable craftspersons and power
engineers. The capacitors must be of the “double bushing” type. For the purpose of testing the perfor-
mance of the floated capacitor, single bushing units may be used with the proper safety precautions.
Beware, though, that the cases of single bushing capacitors will be “live” during the test. Any perma-
nent floating capacitor installation must be of the double bushing type to reduce the safety hazards.
14.4.1 “SEMI-FLOATED” CAPACITORS
A less effective method for reducing Power Influence that results from harmonic currents flowing through
capacitor banks is the “semi-floated” technique.
As detailed in the MITIGATOR Applications Manual, Ground Return Current can be a major component
in noise problems on a telephone line. This current essentially returns to the substation through the
earth ground instead of the power line neutral wire. By doing so, the Ground Return Current “steals”
neutral current and reduces the strength of the canceling magnetic field that the neutral produces. This
reduction in magnetic field cancellation translates into an increase in induction and more noise on the
telephone line.
The Ground Return Current is a side effect of the safety grounding scheme that the power company
uses. Essentially, all transformers, capacitors, etc. are earth grounded, and on long spans, the neutral
may also be grounded at intervals. These earth grounds prevent excessive voltage rise on the neutral in
the event of lightning strike or “power cross” faults.
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