How many parts does the closed track circuit consist of?

Track circuit is a circuit composed of track line and track insulation, which is used to automatically and continuously detect whether this line is occupied by locomotives and vehicles, and also used to control signal devices or turnout devices to ensure driving safety. The whole track system road network is divided into many closed sections according to a proper distance, and each closed section is separated by track insulation joints to form an independent track circuit. The starting point of each section is equipped with a signal (colored light signal). When the train enters the closed section, the track circuit immediately responds and conveys to the signal that there are trains in this section and other trains are prohibited from entering. At this time, the signal light at the entrance of the road section immediately displays the information of dangerous obstacles and no driving.

1870, Dr. W. Robinson of the United States exhibited the model of control signal of open track circuit at the exhibition held in new york. Since then, he has successfully studied the DC closed track circuit, and obtained the American patent in 1872. The track circuit consists of track line, track insulation, power supply, current limiting equipment and receiving equipment. Among them, the track line consists of the track and the lead-out lines at the end of the track and the connecting lines at both ends. Rail insulation is the insulation device at both ends of the rail line, and the insulation device is installed on the track gauge plate, gauge holding rod and switch rail connecting rod. Power supply commonly used DC power supply, AC power supply, pulse power supply, etc. The current limiting device consists of adjustable resistors or reactors, and the receiving device is usually an electromagnetic relay or an electronic relay.

(1) conductor

The conductor part of track circuit includes: rail, connecting splint, lead wire, etc. Among them, the main rail adopts 60kg/M seamless long rail and the factory rail adopts 50kg/M short rail. Connecting clamp plates and leads are mainly used for factory lines, main line folding lines and storage lines.

(2) Rail insulation

The running track circuit of the main track realizes the division of the track circuits of adjacent sections in an electrically insulated way. Electrical insulation is to send/receive the center frequency of this section through the frequency selection of resonant tank circuit. The turn-back line/parking line and track circuit in the depot area are divided by mechanical insulation, including rail end insulation, tank insulation, insulation sleeve and insulation sheet.

(3) Power transmission equipment

Power transmission equipment of power frequency track circuit in rolling stock depot includes power supply, power transmission (step-down) transformer, fuse, etc. The main digital track circuit power transmission equipment includes control board, auxiliary board, power board, coupling unit, induction loop line, tie line and so on. To realize the modulation and transmission of digital information.

(4) Power receiving equipment

Power-frequency track circuit power receiving equipment in rolling stock depot includes step-up transformer, connecting cable and track relay, etc. The main digital track circuit power receiving equipment also includes control board, auxiliary board, power board, coupling unit, induction loop line, tie line and so on. Different from transmission equipment, it receives rail information, attenuates, selects frequency and decodes various digital information, and operates rail relays.

(5) Current limiting resistance

Limit the signal current at the power transmission end and adjust the signal amplitude at the power transmission end.