The interface between HV and LV at the “consumer end” of a power system (“distribution”) is an important part of any earthing designer’s scope of work. Typically, the choice is between a bonding (common) connection between the earths and segregated (or separated) earths. The former is common in kiosk (or “pad mount”) substations whilst the latter is sometimes used with pole-mounted transformers.
For a segregated earthing scheme, Clause B3 in normative Appendix B of AS 2067:2016 states “A minimum separation distance of 4 m is suggested between the HV and LV earthing systems”. This clause goes on to state “In some instances the required separation may be much larger”.
The aim of this paper is to present a systematic computational study of segregated earthing systems and to arrive at a formula that provides a better separation distance than the simple “4 metre rule” in AS 2067:2016. This formula will have soil resistivity (and soil profile) as the dominant variable.