hi charlotte, it sounds like they have inproperly installed the equipment, if that is indeed the source of the interference. Contact the REC (regional electricity company) and report the interference to them, it may be arcing somewhere in the equipment in which case they will want to repair it
can you pinpoint the interference to that substation using a portable receiver? im in the process myself of tracking down a wideband pulse noise that wipes out 17m and makes 20m difficult, so i sympathise!
Martin G7MRV