Stray Voltage: Sources and Solutions

Stray voltage is caused by voltage drop and ground faults and may have its origin on the primary electrical distribution system or on the customer´s secondary electrical system. The rms value of the neutral-to-earth voltage along a primary distribution line may be at a value of zero some distance from the substation depending on the condition of the conductor resistances, grounding resistances, and the amount of load. Neutral-to-earth resistance is not the cause of stray voltage; however, the value of this resistance to earth at a particular location will affect the level of stray voltage. A four-wire single-phase feeder system supplying farm buildings from a single metering point is effective in preventing on-farm secondary neutral voltage drop, provided the four-wire system is extended to all farm loads, and provided no high-magnitude ground faults are present. Isolation of the primary and secondary neutral systems at the distribution transformer is effective in preventing off-farm sources from entering the customer´s system. This separation may be accomplished using a number of commercially available devices.