Occasionally, when power quality problems are related to other loads, to excessive impedance, or to other factors, a “dedicated line” is a reasonable solution.
Other times, when the power issues are related to the utility or the source – not so much. In fact, sometimes power issues get worse when a sensitive load is coupled directly to the source, with no other loads to attenuate higher frequencies.
Here are two snapshot waveforms from a recent site, one from a shared distribution panel, the other from a dedicated line. Can you tell which is which?
The harmonics are visibly worse in the first waveform (3/6/15) – which was a dedicated feed. The shared feeder (3/3/15) still had harmonics but they were attenuated somewhat, presumably by other loads.
The problem here is at the service entrance or facility level – not restricted to a single distribution or sub-panel. The “dedicated line” actually made problems worse!