Harmonic filters

Why dont you try unearthing and see the response? A world without earthing?

Six of one, half-dozen of the other.

Very much so, read the following and check out this link.

Remote earth is defined as an earthing or grounding point that is at the same voltage potential as other points on the earth in the surrounding area. Electrical current flowing through grounding or neutral conductors, or even through earth itself, will cause voltage variation from point to point. The remote earth point is hypothetically "beyond" or outside of the influence of these current paths. Thus, the remote earth point is at zero potential with respect to the voltage source and provides a consistent and repeatable reference point.

Neutral-to-earth voltage (NEV) is a measure of the voltage potential between a neutral-to-ground bonding point and a remote earth point. In essence, any time current is flowing through a neutral conductor, there will be a voltage potential with respect to the earth. This voltage potential can be metallically transmitted over to a remote earth point through code-required grounding and bonding of water pipes, neutrals and other metallic objects. It is important to note that NEV is a normal occurrence caused by the intentional grounding of the power system.

Passive harmonic filters A recent area of research into NEV concern relates to triplen harmonic currents flowing on distribution system neutral conductors. These odd multiples of the fundamental 60-Hz current add instead of canceling out on the neutral conductor, thereby creating harmonic NEV levels. The causes of these harmonic currents include harmonic generating equipment owned by the end user and circuit resonances created by distributed capacitor banks. Harmonics due to customer loads is expected to increase over time as more equipment such as variable frequency drive washers and air conditioning equipment proliferate and as more televisions, PCs and other home entertainment equipment use increases.

While filters for harmonic load mitigation is not necessarily a new concept, applying passive harmonic filters to mitigate NEV impacts on the entire utility distribution circuit is new. In under an ongoing research project, EPRI is working with some U.S. electric utilities to determine how well filters tuned to the third harmonic reduce NEV levels on circuits where the neutral-to-earth voltages have been found to be nearly all harmonic in makeup. The approach used is to convert existing distribution capacitor banks to filter banks by employing a combination of capacitors and one or more inductors. Modeling results demonstrate up to a fivefold improvement with installation of harmonic filters in conjunction with grounding modifications. Harmonic filters appear to be a promising way to reduce NEV impacts on the entire utility distribution circuit instead of at the traditional single point of interest.

Good Luck!