Development of a performance based functional integration policy

Scottish Power´s Transmission business has implemented the integration of protection, control and auxiliary functions within IEDs over a number of years. However, this has been an unstructured incremental process which did not take full advantage of the facilities offered by the current generation of IEDs and a formalised approach was required. This paper describes the motivation and the constraints of the functional integration process. It presents the analysis for an example circuit type and sets out the proposed acceptable arrangements. Consideration is given to the capability of the current generation of IEDs but future developments are anticipated. The paper details the approach to determining the acceptable levels of functional integration which was based on the performance of the protection and control system after integration was applied, compared with the present arrangement of discrete devices which is considered the baseline acceptable level.