【正文】 bits of information concurrently over several separate wires (typically eight or sixteen). Such systems offer faster data transfer rates than serial systems but 外文翻譯（ 原 文） involve far higher wiring costs. For this reason they are not suitable as a universal solution for power system monitoring and control. Serial munications involve the transmission of streams of data one bit at a time over a single pair of wires. Clearly wiring costs are reduced at the expense of overall data transmission rates which are proportionally lower. For monitoring and control applications the slower data rates remain acceptable and serial type munications are used almost exclusively. The munications hardware most monly used by protective relays at present conforms to the EIA’s RS232 standard. This takes the form of the familiar 25 or 9 way 39。s in turn connect to the SCADA work see Figure 1. These RTU39。s power system. This will not happen overnight and it is therefore very important that any chosen system can be installed on a piecemeal basis across a system as it bees required. One of the major factors influencing the take up of relay munications will be the cost to the user. This cost consists not just of the additional cost of the hardware on the relay but also wiring costs, setup and configuration costs and ongoing operational costs. It is important therefore that steps are taken to control all of these cost areas. Set against these costs should be the savings on the SCADA system and the operational savings which result from the increase in system data available. Communications Topology It is possible to connect the SCADA system and the protective relays using a number of different munications topologies. The choice of topology is important as it has a direct bearing on the munications efficiency of the system. 外文翻譯（ 原 文） Figure 1: Simple Protection/SCADA Topology A simple form of connection is to connect each relay separately to remote terminal units (RTU39。 prime function remains the protection of the power system. It is essential therefore that the relays39。外文翻譯（ 原 文） Power System Monitoring and Control Facilities on Protective Relays Abstract: It is now possible to consider integrating the functions of the power system protection systems with those of the local and remote data collection and control systems. A structured approach to this integration is necessary. However, if the full benefits are to be realized. A solution which will solve many of the problems previously associated with this integration is presented together with an example of how it might in future be applied in a typical substation. Keywords: Digital munications, Integration 1. Introduction The current practice in power system transmission and distribution environments is to separate the functions of the local control, protection and supervisory control and data acquisition (SCADA) systems. One reason for this has been the technical constraint that has limited the amount of integration which can be reliably achieved. Local control facilities have consisted of hardwired panels taking up much co ntrol room space. Control logic has been provided by hardwired contacts or programmable logic controllers. Until recently much of the protection equipment has consisted of analogue devices, again taking up much space. Most modern protection devices using electronic and microprocessor technologies have so far concentrated on reducing the space taken to implement traditional protection functions. Generally, SCADA systems have been added more recently and have supplied their own transducers, interface units and wiring. These have grown up in parallel with the local control and protection systems despite the fact that this often resulted in much functional duplication. Where information concerning the protection operation has been required by the SCADA system this has been derived in a secondary fashion, for example, feeding the protection outputs back into SCADA digital input units. Recent technology advances have led to the realization that this degree of duplication is being less and less necessary. Given infinite puting power it could be argued that the information necessary to perform protection functions is all available or can be made available on the SCADA work. It is conceivable then 外文翻譯（ 原 文） that the SCADA system could perform its own protection algorithms and issue its own trip signals through its control work. In practice reliability requirements and the need for rapid fault clearances have limited this approach to a few specialized instances such as long time thermal overload protection. A far more viable approach is to make the information and control facilities within the relay available to the SCADA work. If this is done many of the costs associated with the SCADA analogue and digital I/O systems can be reduced. Additionally, if control facilities provided within the protection equipment are utilized, a central substation puter can also be used to replace much of the local control system. One reason for the failure of systems to integrate protection functions within an overall control package is the sheer amount of processing required. Modern digital protection relays use state of the art microprocessors to provide plex protection functions. When many of these are spread around a substation it is clear that the processing power required to absorb their functions at a central point is formidable. On the other hand the analogue and digital transducers used by the SCADA system are relatively simple devices as are the digital output units. Their equivalents already exist within the protection and making them available to the SCADA system often requires little more than the addition of munications facilities. The ability of the