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Radio modems in a system of heat distribution centres monitoring
11.07.2006 14:25
This application example relates to a district heat supply network, which comprises sixty heat distribution centres. The automation of them is based on programmable controllers, and practically all of them are included in a data transmission system. In the past, the communication media used included commuted telephony network and multi-paired cable connection.
Radio modems provide a new alternative
Wireless transmission possibilities were recently examined, with many trials of different equipment. The ever-recurring problem was connected with the rigid communication protocol between the network and the controllers. The questioning and waiting times of the controllers are fixed, and the tested radio modems could not toggle between transmission and receiving modes as quickly as required.
The trials of SATEL radio modems (SATELLINETM) were completely successful. The switchover times are so short that the SATEL radio modems operating between the computer and the controllers could be compared to a transmission cable. Their simple configuration is an additional advantage; no special software is needed, an ordinary terminal suffices. The radio modems, after careful configuration of the transmission speed and length of character, are therefore ready to operate immediately upon incorporation into the existing transmission system.
Currently, three SATEL radio modems are used in the heat distribution system. One of them is equipped with an omnidirectional antenna and located at the district dispatch room. A computer installed at that site facilitates on-line monitoring of several distribution centres. There are wireless connections via SATEL radio modems between the district dispatch centre and two group distribution centres, located at a distance of ca. 1 km and ca. 2 km, respectively. The transmission quality is excellent, in spite of heavily built area and uneven land.
The future is increasingly wireless
The earlier connections to the specified sites were based on ‘off-line’ transmission (commuted telephone network). The advantages of the new on-line technology are self-evident: easier access to and better control of individual parameters, better organization of the alarm system, possibility of registering and analysing parameters on one terminal, facile operation and enhanced transparency of the entire system, and lower failure rate compared to rather high rates with telecommunication lines and telephone modems.
In particular, in areas where the cables are yet to be laid, and such enterprise were to prove impossible or too costly, radio modems are the best choice. Thanks to them, the entire system can be standardised.
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Heat distribution (in pdf form)