20 : 10 : 39 : 22 . Use of remote reference electrodes. In preparation for testing, a remote reference electrode must be installed and penetrate the soil to a depth of approximately 30 inches. When practicable, the remote reference electrode shall be installed at least 25 feet away from the nearest underground conductive electrical equipment, of any type, or at a distance equal to three to four times the buried depth of any metallic structure connected to the service entrance neutral. When practicable, the remote reference electrode must be located no closer than 25 feet from the centerline of a primary electrical conductor right-of-way and no closer than 100 feet from the edge of a transmission line right-ofway.

The remote reference electrode shall be checked for remoteness before being used for tests or measurements, and, if found to be insufficiently remote, a new location for the remote reference electrode shall be found and retested for remoteness. Remoteness of the remote reference electrode is determined by measuring the voltage from the transformer grounding electrode to the remote reference electrode. The ground electrode resistance and current at the transformer are also measured.

Remoteness is adequate if the measured voltage between the transformer grounding electrode and the remote reference electrode is within 20 percent of the voltage calculated by multiplying the transformer grounding electrode current by the transformer grounding electrode resistance.

If the transformer grounding electrode is within 25 feet of other primary or secondary grounding electrodes, the remoteness test shall be conducted at the first primary system grounding electrode upstream of the transformer that is greater than 25 feet from other primary or secondary system grounding electrodes.

Source: 42 SDR 174 , effective June 21, 2016 .

General Authority: SDCL 49 - 47 - 2.

Law Implemented: SDCL 49-47-2 , 49 - 47 - 3 .