What you'll need to do is use a filter barrier to limit the results (a condition barrier would cause your upstream trace to not locate a source). Its pretty typical to look for the upstream transformer, protective device, etc but I'm not aware of a way to find the first upstream feature.
If you really do want the first upstream feature than one potential workaround would be to do an upstream trace using the connectivity results type and just look at the features that are directly connected to the current feature. In the case of loop or bi-directional flow this may be multiple features.