Abstract :
As modern protection, instrumentation and control devices are microprocessor-controlled (“numeric”), they can support remote communications in addition to their main protection, monitoring, control or logic functions. The benefits of remote communications are numerous. Information and statuses from a number of substations can be accessed at a central point remote from them. Information is presented on computers for operators to monitor and respond to as appropriate. This information may be displayed graphically on mimic diagrams or trends, or in prioritised lists, or in alarm banners, and can be archived. Displaying information centrally means some instrumentation need not be used at the substation, reducing instrument costs and panel space requirements. Remote communications reduce the need for site visits, as maintenance visits can be organised only when necessary, as plant can be controlled from the central point, and as events such as protection operations can be analysed at the computer. A protocol defines the commands and requests which can be sent to the remote equipment and the allowed responses and data formats which can be returned from it. The protocol allows the remote control centre to both access and poll information from the substation equipment, and to send commands and control actions. The features of substation protocols are discussed as are the need for standardisation and integration of remote equipment
