The RTU Communicator is a server for communication with remote terminal devices which use the communication protocol HioCom or HioCom2 (RTUs, RPS II, diagnostic cards MPC), communication protocol IEC 60870-5-101 or IEC 60870-5-104 (IEC 61850 optionally). It collects a data from the connected terminal devices and enables the control of these devices. It runs in the background of the operating system as its service. The actual status of the signals and measurements (only for these transmitted via protocols IEC 60870-5-101/104) can be browsed on the service web interface. The communicator itself does not have a user interface; it is implemented by the RTU User center. This pair of applications must be completed by the database server Microsoft SQL.
- server for communication with the RTUs and similar equipment (redundant power supply RPS II or diagnostic cards MPC),
- communication gate or concentrator between the control and visualization system and the RTUs,
- communication with RTUs through the TCP/IP network by TCP and UDP communication protocols,
- communication with RTUs through the RS485 network and RS232 line,
- standards DDE and OPC, communication protocols IEC 60870- 5-101, IEC 60870-5-104, IEC 61850 (optionally),
- operation on the background as OS service,
- configuration in the database and/or in XML file,
- storage of records from RTUs into files,
- recording of values into daily files,
- recording of communication with units into the file,
- recording of communication with control and visualization system into the file,
- recording of fault and operating messages into the file,
- option of redundant application in hot backup mode.
Communication on the line
The RTU Communicator, in addition to the standard implementation of the IEC 60870-5-101 protocol, has implemented a special optimizing algorithm for communication on the line. The line communication is optimized for the radio network with high latency where commands from the control station must be sent preferably before less critical data. During the command, the stated communication channel is reserved only for the control which ensures the shortest possible time for the execution of the command and gathering back information about the execution. For communication on the line, it is not necessary to implement any additional configuration. The Communicator itself detects a way of communication with slave devices on the basis of the presence of one or more devices under one communication interface.
External data interfaces
The communicator can provide a collected data to other applications through its external data interfaces. The applications can also control terminal devices by means of these interfaces.
The Communicator has three interfaces:
- DDE – interface uses DDE technology,
- OPC – the interface uses OPC technology. The interface is implemented through the DLL library which operates without the license only for the first 30 minutes after start of the Communicator. For full operation, the Communicator with OPC license must be purchased,
- IEC-104 – operates according to the standard IEC 60870-5-104, in the role of TCP server.
Implementation of the RTU Communicator
The most common implementation of the RTU Communicator is use as a part of the Communication set delivered to the RTUs (including the SQL server in the Express edition). In this implementation, the Communicator is used as a parametrizing tool, so external data interfaces are not used. The configuration of the parameterized units is stored in the database or in an XML file. No extended license is provided for the Communicator, at the stated moment it is possible to communicate only with one RTU. All Communication set programs are installed on one computer and the Communication set is a single user.
A further type of implementation is the independent concentrator or communication gate. The Communicator is used this way if there is demanded a mediator between RTUs and SCADA. It is presumed that the number of terminal units is static. Then it is possible to apply the Communicator independently without the User center and without the MS SQL server, to set it for using an XML file as a storage area for configurations of RTUs and to exploit some of its external interface. In this case, it is necessary to purchase the Communicator with the expanded license for the appropriate number of terminal units. To achieve the redundancy, the Communicator can be doubled.
If the mediator is required between the SCADA system and the RTUs but it is presumed that during the operation the system will be expanded or decreased or that the configuration of the units will be changed during the operation, it is recommended to apply the whole Communication set in the role of the concentrator or the communication gate. The Communicator is then installed on the central server and is set so that the storage of the configuration only uses the database. The SQL server is installed either on the same computer as the Communicator or on another central server. The User centers are installed on client computers. Such an implemented Communication set is multi-user and it is necessary to purchase the Communication set with the expanded license for the appropriate number of terminal units and for the appropriate number of the User centers installations. By doubling the Communicator, eventually also the MS SQL server, it is possible to achieve a redundant character of the operation in the hot backup mode (the detailed description is in the chapter about the RTU Communication set).