1、外文翻译（ 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 i
2、s 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 communications, Integratio
3、n 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 amo
4、unt of integration which can be reliably achieved. Local control facilities have consisted of hardwired panels taking up much control room space. Control logic has been provided by hardwired contacts or programmable logic controllers. Until recently much of the protection equipment has consisted of
5、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 t
6、heir 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 h
7、as 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 becoming less and less necessary. Given infinite computing power it could be argued that
8、the information necessary to perform protection functions is all available or can be made available on the SCADA network. It is conceivable then 外文翻译（ 原 文） that the SCADA system could perform its own protection algorithms and issue its own trip signals through its control network. In practice reliab
9、ility 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 network. If this is
10、 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 computer can also be used to replace much of the local control system. One reason for the
11、 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 complex protection functions. When many of these are spread around a substation it is c
12、lear 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
13、 making them available to the SCADA system often requires little more than the addition of communications facilities. The ability of the protection equipment to replace much of the local control and SCADA I/O systems hinges on the ability of the protection equipment to communicate in a structured an
14、d deterministic way. It is essential that the protection performance is not compromised whilst at the same time the requirements of the local control and the SCADA systems are still met. From the local control and SCADA point of view the principal requirements are for analogue inputs for measurement
15、 and data logging, digital input data for annunciators and alarms, and digital outputs for controlling plant. Most measurement data is used for general indication purposes where an accuracy off 5% is sufficient. Analogue and digital data used for visual indications and data logging require scan rate
16、s of around once a second. Where sequence of event recording is required relative accuracy across the system is more important than absolute accuracy. Generally a resolution of 1ms should be aimed for. Control response times should be around 200ms. 2. Protective Relay Communications 2.1 Communicatio
17、ns Philosophy 外文翻译（ 原 文） The protective relays prime function remains the protection of the power system. It is essential therefore that the relays protection performance is not compromised by the requirements of data monitoring and control. For this reason it is considered necessary to provide moni
18、toring and control communications separate from any communications requirements of the protection. Thus in a blocking scheme for example, blocking signals would be transmitted over their own protection signaling link e.g. pilot wires, and not over the monitoring and control communications link. In t
19、his way the deterministic behavior of the protection is maintained. Also, there remains those users who do not yet need some or all of the features available .It is important for these users that the operation of the relay does not depend on the monitoring and control communications link and that th
20、e full protection capabilities can still be realized when such links have not been installed. The full benefits of relay communications will only be achieved if they can be installed at all the relevant points on a utilitys power system. This will not happen overnight and it is therefore very import
21、ant that any chosen system can be installed on a piecemeal basis across a system as it becomes required. One of the major factors influencing the take up of relay communications will be the cost to the user. This cost consists not just of the additional cost of the hardware on the relay but also wir
22、ing costs, set-up and configuration costs and on-going 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. 2.2 Communications Topology It is possible to connect the SCADA system and the protective relays using a number of different communications topologies. The choice of topology is important as it has a direct bearing on the communications efficiency of the system.
