The Hungarian defender, recalled this week into his national team squad, was given a straight red card for a challenge on Darius Henderson.
"I had the ball, everybody can see that," Gyepes told the Echo.
"I'm always honest and it was a great tackle, the ball goes off in the other direction, but the referee did not see that.
"Even Henderson got up and told Jay Bothroyd that he thought it was not a penalty.
"I just can't understand it.
"I took the ball away from Henderson and the ref gives a penalty - it's crazy.
"I've never been sent off in my life, so I can't understand how this has happened.
"How the referee can make a decision like that from the halfway line I don't know.
"The referee killed the game and the club will be appealing on my behalf."
Since winning a place in the starting line up Gyepes has become a fans favourite and one of the best defenders in the Championship. The red card awarded against him was quickly followed by a second red for Ross McCormack effectively ending the game as a contest. Cardiff are appealing both red cards.
"You cannot play 11 against nine, no way," Gyepes continued. "We are all disappointed and know that the result would have been different 11 against 11.
"Now we have to pick ourselves up the next time we play and get a win to put us back on track.
"It is so disappointing because it was not a good game and the referee spoilt the whole game."