Unlike Test cricket, the fielders are spread out to save runs in limited overs cricket. The powerplay rule (Restrictions on the placement of fieldsmen), along with a number of other factors, has contributed to the big scores (300+) in modern One Day Internationals.
ODI and Twenty20 differ in terms of the number of overs where mandatory powerplay rules apply. The rules below apply only when a match is uninterrupted.
The first six overs of an innings will be a mandatory powerplay, with only two fielders allowed outside the 30-yard circle. Beginning with the seventh over no more than five fielders will be allowed outside the 30-yard circle.
Fielding restrictions evolved through the 1970s, notably in World Series Cricket, and were first introduced in ODIs in 1980 in Australia. The most common rule was for only two fieldsmen to be allowed outside the circle in the first fifteen overs, then five fieldsmen allowed outside the circle for the remaining overs.
The powerplay moniker was introduced by the International Cricket Council in 2005, when the fielding restrictions were split into three blocks: the mandatory ten overs at the start of the innings and two further five-over powerplays with the bowling team being able to choose the timing of both. In practice though, both were generally taken as soon as possible, effectively leading to a single block of 20 overs of fielding restrictions. To counter this, in 2008, the batting team was given discretion for the timing of one of the two powerplays.
From October 1, 2011, the ICC brought additional changes to the bowling and batting powerplays. Under the new rules, in a 50-over match, neither powerplay may be taken before the start of the 16th over and both must be completed before the commencement of the 41st over, so overs 11 to 15 and 41 to 50 cannot be powerplay overs. Should either or both teams choose not to exercise their discretion, their powerplay overs will automatically commence at the latest available point in the innings (e.g. in a 50-over innings with one unclaimed powerplay, it will begin at the start of the 36th over).
On October 29, 2012 The International Cricket Council made further amendments on powerplays, reducing the number of blocks of Powerplays from three to two.
From 1992 to 2012, during non-powerplay overs a total of five fielders were allowed outside the circle. This was changed to four in October 2012. Moreover, from 1992 to 2005, two fielders were required in catching positions in the first fifteen overs. This was reduced to first ten overs (Powerplay 1) in July 2005.
From July 5, 2015 The ICC further amended the Rules making the whole innings as a composition of 3 Powerplays, thus removing the Batting Powerplay introduced last time. Furthermore, the restriction of two catching fielders in first powerplay was relaxed.
Content from Wikipedia