Neutral Isolation Devices

Isolating transformers have been used, rather extensively, to create a separate grounded neutral system on the farm. An isolating transformer represents a $1,000 to $3,000 investment plus the operating losses of the transformer. They must be properly installed and meet the prevailing codes and recommendations, particularly for overcurrent protection, bonding, and grounding.

Several types of conventional low-voltage lightning arresters can also be used for neutral isolation. Since most of these devices have low-current capacities, their use may be restricted to systems with appropriate limitations on fault currents.

Saturable Reactors designed to give an impedance-change threshold in the range of 10 to 24 VAC are also in use. Below saturation voltage, the high impedance provides isolation. Above saturation, the impedance drops to a very low level to provide neutral interconnection.