I'd be amazed if the ipad still works. Buy new connector and try. You could plug connector in first then power second. Don't touch anything. May want to connect to surge protector. Protector will drop before power line. I wouldn't be surprised if there was a fuse on the 5volt line.
The charger reduces the voltage down to what the iPad can accept. From this page, it looks like the iPad accepts 5volts. In my knowledge of electronics, 5 volts is safe.
http://www.wired.com/2013/12/charging-devices-faq/
Here is all about the use of the thirty pins. Light on how charging works. USB charging is at 5 volts. See comments.
http://irq5.io/2012/06/25/the-apple-30-pin-dock-connector/
google search of ipad 30 pin connector
connectors from a-z.
Take to a computer repair stop and see what they have to say.