Check Your Shorts
New member
I am an electrician with industrial and commercial experience and have recently started working at a mineral exploration site that will become an underground hard rock mine at some point. The former electrician installed a lot of substandard work which I am trying to correct in accordance with the NEC as it applies to the above ground and surface areas of the operation. The problem I am addressing currently has to do with a generator-fed power station that supplies the sumps and drill rigs underground.
The MLC is fed from a 480v IR G570 generator, capable of up to 683 amps; safety switch fused at 400a. The MLC feeds a 480v-4160v transformer which transmits power to a 4160v-480v MLC/transformer combination unit underground. The former (self-proclaimed) electrician had driven some 1" rebar into the ground around each of these units and wrapped them in wire mesh (what you would find reinforcing concrete) to act as fencing. This is noncontinuous sections tie-wired together and stands at about 5.5 to 6 feet high. The gates are also jury-rigged. Each MLC and the stand-alone surface 4160 transformer have one piece of # 1/0 stranded bare copper wire running to a ground rod and no grounding/bonding provided for the fencing. I also suspect a complete lack of anything remotely resembling grounding grid.
Can anyone assist me by pointing out some resources I need to research in order to correct this atrocity? I have worked around many transformers but have not had the experience with a high voltage power station since doing work for the Big 3 automakers as an apprentice nearly 15 years ago.
Additionally, the grounds are attached via bolt-on mechanical lugs and are also in a very salty sea-air environment in the Pacific Northwest. Am I right in guessing this grounding and bonding needs to be exothermic (Cadweld)?
Thanks a million.
The MLC is fed from a 480v IR G570 generator, capable of up to 683 amps; safety switch fused at 400a. The MLC feeds a 480v-4160v transformer which transmits power to a 4160v-480v MLC/transformer combination unit underground. The former (self-proclaimed) electrician had driven some 1" rebar into the ground around each of these units and wrapped them in wire mesh (what you would find reinforcing concrete) to act as fencing. This is noncontinuous sections tie-wired together and stands at about 5.5 to 6 feet high. The gates are also jury-rigged. Each MLC and the stand-alone surface 4160 transformer have one piece of # 1/0 stranded bare copper wire running to a ground rod and no grounding/bonding provided for the fencing. I also suspect a complete lack of anything remotely resembling grounding grid.
Can anyone assist me by pointing out some resources I need to research in order to correct this atrocity? I have worked around many transformers but have not had the experience with a high voltage power station since doing work for the Big 3 automakers as an apprentice nearly 15 years ago.
Additionally, the grounds are attached via bolt-on mechanical lugs and are also in a very salty sea-air environment in the Pacific Northwest. Am I right in guessing this grounding and bonding needs to be exothermic (Cadweld)?
Thanks a million.
