The wide spread development and implementation of IEC 61850 based Substation Protection, Automation and Control Systems (SPACS) using predominantly GOOSE messages and client/server communications has raised the awareness of the industry regarding the benefits of communications based systems. At the same time, the last years have seen a significant change in the availability of stand-alone and embedded Non-Conventional Instrument Transformers (NCIT) with IEC 61850 sampled values interfaces.For this reason, the testing of fully digital functional chains has become an important issue with the deployment of IEC 61850-based substations using Stand Alone Merging Units (SAMU), and/or NCIT and featuring both station bus (IEC 61850-8-1) and process bus (IEC 61850-9-2).This Brochure covers all test related aspects of a fully digital SPACS and equipment, including NCIT/SAMU Certification tests, SPACS level Interoperability tests, Factory Acceptance Tests, Commissioning and Site Acceptance Tests and Maintenance tests after commissioning