I'm afraid this one is certainly a case where if you need to ask what you need know, then you're not going to get the job.
I've worked with HV in electronics regularly, e.g. measuring 1 to 4kV supplies for high-power transmitter stages, etc. and feel quite comfortable doing so, but that's still a world apart from 4kV power distribution systems. I would certainly need to learn from those more-experienced for the latter.
