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remote control equipment - Indian Railways Institute of Electrical ...

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The configuration used in Railway SCADA system is party line one-on-a-few<br />

configuration. Here master station communicates with the RTUs via party line (shared)<br />

communication channel. In this case a unique address is required for each RTU on the<br />

channel.<br />

This Configuration has the advantages <strong>of</strong> sharing the master station communication<br />

logic and the advantage <strong>of</strong> sharing the communication channel.<br />

7.2.4.2 Communication Media<br />

Availbale communication media options are<br />

* Metallic cable pairs<br />

* Power line carrier (not used in indian <strong>Railways</strong>)<br />

* Microwave<br />

* Leased circuits<br />

* Fiber optic cable<br />

* Satellites (not used in <strong>Indian</strong> <strong>Railways</strong>)<br />

As on date only metalic cable pairs and fiber optic cable are <strong>of</strong> interest, only these<br />

options are discussed below :-<br />

7.2.4.3 Metallic cable pairs<br />

Cables have the advantage <strong>of</strong> involving little new technology and so it is easy to<br />

consider the use <strong>of</strong> cable pairs for data transmission, where typically, one such pair can be<br />

used for simplex or half duplex transmission at speeds upto 2400 bits per second.<br />

Cables, as with S&T installations must typically be protected against induced voltage<br />

surges or lightening strikes by protective devices such as gas tube protectors and in addition<br />

if entering a high voltage substation, must be protected from huge difference in adjacent<br />

ground mat potential during substation fault current conditions through the use <strong>of</strong> addtional<br />

devices such as neutralising transormers.<br />

7.2.4.4 Fiber Optic Cable<br />

Fiber optic cable sytems that are used for communications are made <strong>of</strong> three basic<br />

components. The first component is a long fiber <strong>of</strong> very pure glass or plastic that permits light<br />

to travel from the transmitor to the third component i.e. receiver. The reveiver converts the light<br />

signals back into electrical signals. The signals can be either analog or digital.<br />

In addition to these three components, there are repeater where the light signals are<br />

converted to electrical signals amplified and converted back again. Splicing devices are also<br />

necessary in order for signals to travel from one fiber to the others with minimum attenuation.<br />

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