Top disc: Dummy – never measured Second disc: Sampled every two years Third disc: Sampled once a year Fourth disc: Sampled at 6 month intervals Fifth disc: Sampled at 3 month intervals Sixth disc: Sampled monthly Bottom disc: Dummy
Table 1: Link Between Pollution Index & Pollution Class |
Pollution Index(µ S / cm) |
Pollution Class |
0 – 75 |
I: Light |
76 – 200 |
II: Medium |
201 – 350 |
III: Heavy |
> 350 |
IV: Very Heavy |
Photos: INMR © as well as to the individuals responsible for each substation as well as their supervisors.
One of the DDG and reference string sites that form part of Watson’ s monthly‘ circuit’ is 400 kV Aurora Substation, located several hours drive north of Cape Town. Already about 40 years in service, the site is surrounded by mostly barren land but still classified as polluted due to nearby steel mills as well as the coastline.
Not every DDG and reference string site is at a substation. For example, these are also installed at a place called Haksteenpan, in the Kalahari Desert bordering Namibia. The area is mostly wilderness with no major substations nearby but is still considered important to monitor from a pollution standpoint since a new transmission line is planned to pass nearby. Watson points out that the specific location selected for the DDG in this case is on the crest of a hill which feels the full impact of dust blown from off a nearby dried salt lake bed. also equipped with a full-scale meterological station enclosed in a shipping container, provides a good example that unpredictable events can sometimes occur, such as a herd of passing cows knocking into and tipping the DDG.
I |
Steps in measuring ESDD level on different discs in reference string. |
Another similar test location is outside the northern city of Uppington, where a new solar generation facility will be built using concentrated sunlight to drive turbines. The site, which was |
I |
Reference string at cement plant shows impact of localized very heavy pollution. |
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