GENERALLY speaking, Soy Powder is more like Soy Flour (roasted, ground soybeans) than it is like Soy Protein Isolate (ONLY the protein fraction of the soybeans). For example, there is a Fearns brand-name Soy Powder in the US. I've only ever found Soy Flour or Soy Protein Isolate or Soy Milk Powder here in Canada.

It will depend very much on where you are reading "soy powder" and (if it's on a package) what the nutritional information label says.

Have you tried doing a websearch on "Soy Powder", on www.google.com for instance? Do you have a brand name or was this in a recipe? If in a recipe, what's the context (what's the recipe)?

Very difficult to answer your question with so little information.