I have been searching the web, codes and standards for more than two days looking for help and I feel frustrated. I need the grounding design requirements for a 13.8KV/480V substation located on an upper building floor. I have the IEEE Std 80-200 "IEEE GUIDE FOR SAFTY IN AC SUBSTAION GROUNDING" but this standard is mainly applicable for outdoor substations. In addition, the NEC falls short for this application. Has anyone come across this situation before?