When sorting by votes, the accepted answer is promoted to the top, regardless of votes - unless it's a self-answer, in which case normal vote sort is used without promotion.
See also:
http://blog.stackoverflow.com/2009/01/accept-your-own-answers/
No change in sort order. Normally, accepted answers are “docked” under the question. This is not true for owner accepted answers; they stay in standard sort order like any other answer.
Accepted self-answers aren't pinned to the top.