Bigjabe
Member
- Location
- Vancouver BC
I don't think that would work due to the M421 Clause 4.8.2.1. The LA's need to be at the mine end of the o/h line, perhaps also at the isol sub end.
4.8.2.1
Where power feeders serving underground workings are connected to overhead lines longer than 90 m,
lightning arresters or surge capacitors shall be installed at the point of connection to the underground
feeders.
Agreed, even if it's not against code, I still don't like it.
- isol subs bonded to main sub via overhead shield wire
- 15kV AIS at the main sub
- we will have LA's at the isol sub end, and yes bonded to sub frames... but we also need LA's at the u/g mine end of the overhead line, at least such is my interpretations of M421.. I think connecting LA's at the mine end to an isolated bed is the only way to prevent GPR at that the mine, but lightning strikes on fans, etc will still cause problems underground. I will consider moving isol subs to right near the boreholes, then connecting NGRs and u/g ground conductors via insulated wire to a remote bed. Power cables going u/g would need armour, shields and ground wire isolated at the surface end.
