Hi Kieren,
You do this by creating a CategoryComparison object, and setting it in the TraceConfiguration, like this:
CategoryComparison categoryComparison = new CategoryComparison(CategoryOperator.IsEqual, “Protective Device”);
traceConfiguration.Traversability.Barriers = categoryComparison;
If you haven't read it already, this doc walks through all of the different trace classes and how they are used. Also, we have a Load Report sample that demonstrates the use of a CategoryComparison.
I hope this helps. Please let us know if you have further questions.
--Rich