Your whey powder is almost certainly still good.
Unless the container you have it in isn't air tight or you've had it opened a lot. Water pulled out of the air (humidity) is what bacteria would use to digest it. Heat can also degrade things. Without water or heat, it's basically inert. Expiration dates are estimates based on average use/care.
Example - How long would your milk last if you put it in the freezer? (assuming the carton didn't explode on you first..)
If you've kept it air tight and away from heat, it's still good.