Powell's acrobatic effort in the 24th minute gave the hosts a two-goal cushion after Neil Danns' early opener, looping over Andy Lonergan in the Wanderers goal and into the corner of the net.
The 19-year-old forward capitalised on Chris McCann's deflected shot to score his fourth goal since starting his loan spell at the DW Stadium. Powell was booked late on, but that won't spoil his derby day celebrations. Reds striker Will Keane was an unused substitute for the Latics.
Meanwhile, in Belgium's Second Division, Davide Petrucci came off the bench as Royal Antwerp rescued a point away to Geel. The United youngster entered the match shortly before the hour mark and was therefore on the pitch as his loan club scored in the 89th and 90th minutes to force a dramatic 2-2 draw.