Ungrad - ABB-Relays Switzerland
Kristensson - ABB-Relays Sweden

It is a trend to introduce digital technigues for control protection and several other tasks in the substation. Advan rages are achieved in speed, capacity, flexibility, selfsuper vision, availability, and other characteristics. Also a reduction of the required space for hardware and cabling can be achieved. At the same time it becomes possible to interchange in formation by means of a data link vetween the substation's sec ondary equipment and also with the network control System . A survey has shown the different tasks of secondary equipment in substations, and the increasing requirements. The survey has also shown the possibilities to match them with digital techniques. Examples of systems available today are given and the possibilities future systems will give listed. A user is confronted with different systems available on the market. New digital equipment must be combined with existing analogue equipment. Different combinations can be made , according to the proposed multi-use of inputs, the degree of integration of different functions, the used standards , the service structure and the division of responsibility within the user's organisation etc. A lot of details, normally not included in the data sheet, are to be ovaluated. Therefore a checklist made by a user is presented, listing the necessary information to be collected.