A lot of distribution substation earthing design is standardised by utilities and can be completed in a relatively routine manner, but occasionally scenarios appear which do not easily fit the standard design mould and needs the attention of an experienced earthing engineer.
This presentation will cover two such scenarios which are becoming more common in Tasmania. The first is a temporary HV embedded generator site which was established to provide supply to a rural township, the โtrickyโ element being the proposed siteโs location being on customer land near a residence and MEN stakes. The second is a typical distribution design conundrum: the โsmall industrial customerโ supply substation, where a small isolated site requires a ground mounted supply and the designer must work through the decision of separate vs common earthed configurations, whilst keeping the site as safe as possible in the long term.
There are a couple of key lessons we will extract from these scenarios, such as:
- The design assumptions that are required in estimating the expected MEN system performance and how they can vary (wildly) in practice;
- Why reaching the negligible risk threshold is not necessarily enough to stop considering more options in your design process.
- Factors external to the immediately technical aspects of a design that affect it, like time pressures, assumptions behind customer behaviour, and long term asset management considerations; and
- The benefits on on site performance ย testingย