Grounding resistance in mine area
Grounding resistance in mine area
(OP)
We are trying to limit Ground potetial rise in mine area to 100V or less. The system ground fault is 500A in 69kv system. The only way of achieving it is to limit Mine Substation resistance to 0.2 Ohms. We have only 2 substaions in mine area, fed from 69KV Substation via overhead lines. We could ground some poles or drill deep ground wells, or add a isolated ground bed. Want to know the pro and cons of each option. Thanks in advance.






RE: Grounding resistance in mine area
1. Put the step-down transformer outside of the mine area, and install a resistor in the neutral to minimise the fault current. Ensure that there are no connections between the mine earth grid and the step-down transformer substation.
2. Ignore the utility contribution to ground potential rise and adopt a "head in the sand" approach.
Neither has tried to lower the earthing resistance to such a low level.
RE: Grounding resistance in mine area
RE: Grounding resistance in mine area
RE: Grounding resistance in mine area
RE: Grounding resistance in mine area
Just a thought.Can't we have a high resistance grounded system?
RE: Grounding resistance in mine area
RE: Grounding resistance in mine area
I cannot explain the 25 feet requirement other than it is a law. However, if the three phase power from the station stays on the surface (portal building, ventilation fan, water pumps, etc.), and does not enter the underground area of the coal mine, there is no requirement to establish this 25 foot separation distance, whether it is resistance grounded or solidly grounded.
I am not sure what type of mining you are involved with, but the laws that govern coal mining in the US can be found in 30CFR (Code of Federal Regulations) - Part 75 (Underground) and Part 77 (Surface). The website is www.msha.gov. MSHA is the Mining Safety and Health Administration.
Dave