Creation of SSD and Excel signal list: Once the single line diagram, bay and station level functions are specified a substation specific list of required signals can be produced. Ideally description fields and SCL extensions could be used to deliver non IEC 61850 information in the library (such as Vattenfall process names and operator texts) to the supplier within the Substation Specification Description (SSD) file. However, most gateway and SCADA engineering today is based on using Excel templates and Vattenfall engineers are most familiar with reviewing gateway configuration in this format. To adapt to today’s work practices the specification is therefore also exported in Excel format. An excerpt of the signal list at specification phase is shown in Figure 7