Rhys McCabe gave the hosts a 20th-minute lead with a superb volley and Jeremy Helan added a second in stoppage time with a good, angled finish.
Sutton's failure to award a penalty after Yann Kermorgant appeared to be fouled in the area was one of the incidents which frustrated Powell and he was forced to watch the second half from the directors' box, although he was told by the referee that it was not an official sending-off.
Powell said: "There were a number of incidents that angered me during the first half and I went to the referee at half-time and asked him about a penalty we didn't get.
"There was a goal ruled-out for off-side which was actually on-side and there were also a number of fouls on my players.
"I was asking for consistency and fairness but I didn't swear at the referee or point at him. He sent me to the stand because he said it was for the image of the game. He said I'd left my technical area but it was half-time so what was I meant to do?"
Sheffield Wednesday manager Dave Jones had some sympathy with Powell's point of view over the Kermorgant incident, saying: "It looked a penalty but the referee has got to make a quick decision and maybe it's that little of luck we've been missing."
But Jones felt the result was fair and said: "We had a shaky start and they could have scored a goal in the first two or three minutes but after that we sorted ourselves out and I thought we were worthy winners in the end.
"Rhys McCabe scored a great goal and he's certainly capable of doing that. We've seen him do it a lot in training and I'm just pleased for him because he's a good young player who's learning his trade.
"There's a long way to go and we're fighting for our lives. What we maybe lack sometimes in terms of a little bit of quality, we make up for in endeavour and commitment and that's all you can ask for. As today shows, if they work hard and keep that going, they'll win more than they lose."
- Sports & Recreation
- Yann Kermorgant