Power play is when the fielding restrictions come in. There are three. The first Power Play is the first 10 overs.. the second and third, however, are at the discretion of the fielding captain. In some cases these have been used "off the cuff" (meaning a change from 15 to 20 overs at the start of the innings)... but what tends to happen when you've got an opener running riot is 10 overs off the cuff.. and then a Power Play at the fall of a wicket (when batsmen might look to consolidate).

Australia make 293 off 50 overs: http://uk.cricinfo.com/db/NEW/LIVE/f...09OCT2005.html