Either what pinhead said, maybe volt reg? Those normally do the opposite though. Its sure not anything normal other than bad battery or bad volt. reg.  o you have a manual? My haynes has got a ton of alternator/charging system troubleshooting methods. Might want to run through those.
I didn't say you wouldn't fry anything!
30 amps flowing into your battery when its not needed is not good. Might want to get out the multimeter and see if there really is 30 amps flowin out of the alternator, maybe something is lying to you.
I had the same a year ago, which is bad for the battery. Cause was a bad voltage regulator. It is possible to adjust the (mechanic) regulator according to the engine manual. But I replaced my old regulator with an electronic type. Works fine now.
I'm a '74, it may be the same, its mounted to the engine side of the firewall, stand next to the DS front tire and look under the brake/clutch master cylinders. Black nondescript metal box with a 3 wire plug, sticks out about 3 inches from firewall, 1.5 inches wide, about 3.5 inches long. Since your's may have the ps mounted alt. not sure where your volt. reg is.
Here's a pic. Kinda close up but should give you an idea. Napa has it, $20-30. If I were you I would try the solid state swap listed in Tech while you're at it. Less fluctuation, more sensitive, temperature senstive as well.