Components Track circuits UM71

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Myra Ferguson
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1 Components Track circuits UM71

Track circuits UM71 An essential element of railway safety, the track circuit detects the presence or absence of any vehicle on a given stretch of track.

3 Track circuits UM71 An essential element of railway safety, the track circuit detects the presence or absence of any vehicle on a given stretch of track. Jointless track circuits avoid the mechanical cutting of rails, the traditional insulating joints being replaced by tuned circuits. Ansaldo STS France offers a comprehensive line of UM 71 products allowing the use of jointless track circuits under a variety of conditions. Advantages High reliability: proven by more than track circuits in service. Safety: equipment agreed by the SNCF. Low cost: reduced impedance of traction power return circuits, thus avoiding power losses; no requirement for heavy and costly inductive connections; reduced track maintenance. Immunity: total for all types of electric traction as a result of the frequency- modulated signal. Quality: each item of the UM 71 product line is delivered with its factory test report. Use Un-electrified track, DC or AC electrified track with the traction current return circuit through both rails, version adapted to the cabsignal function. Principle of Operation A UM71 track circuit is generally terminated at each end by an electrical joint to a transmitter or receiver via a matching unit (Tad). An insulating joint may also be used in place of the electrical joint at each end or at both ends of the track circuit. Electrical joint The length of track included in the electrical joint is terminated at each end by a tuning unit (BA) or (BU). Each tuning unit consists of an inductor and capacitors for obtaining: parallel resonance with the track inductance (impedance pole) at the frequency of the involved track circuit. serial resonance at the frequency of the adjacent track circuit. this serial circuit shunts the track, thereby preventing propagation of the signal beyond the limits of the track circuit. A track air-core inductor connected (SVa or SVac) to the midpoint of the electrical joint optimises performance and balances the return traction current between the two rails. Termination on an insulating joint This is provided by the connection in parallel of an air-core inductor and a tuning unit. The continuity of the traction current return circuit is provided by: the mid-point of the track air-core inductor (up to a permanent load of 200 A) in the case of AC electrification, a matched inductive connection in the case of DC electrification. Alternation of frequencies The track circuits use different frequencies to avoid crosstalk between adjacent sections of track. our types of track circuit are thus used: 1700 Hz track circuits and 2300 Hz track circuits on one track, 2000 Hz track circuits and 2600 Hz track circuits on the parallel track. Compensation This process developed by Ansaldo STS France increases the maximum length of UM 71 track circuits. It consists in improving transmission along the track by connecting capacitors of appropriate values between the two rails and buried in the ballast at given intervals. Since 1980, compensated UM 71 track circuits installed by the SNCF have proven their excellent reliability over more than 3000 km of track. 1

Application and performances The typical application illustrated below corresponds to ballast having a minimum resistance of 2 ohms per km and a maximum theoretical shunt resistance of 0,25 ohms

4 Application and performances The typical application illustrated below corresponds to ballast having a minimum resistance of 2 ohms per km and a maximum theoretical shunt resistance of 0,25 ohms between the transmitter and receiver of the track circuit. Under these conditions, detection of a broken rail between the transmitter and receiver of the track circuit is ensured. Ansaldo STS France has developed simulations software enabling users: to determine the transmission characteristics of their railway tracks, to determine the optimum adjustments of the track circuits. Typical installation of UM 71 track circuits In all cases: typical length of electrical joints on 1,44 m tracks: 2 x 13 m (with BA) // 2 x 10,20 m (with BU). Connection of tuning units and air-core inductors: 75 mm² multistrand copper cable. Connection of transmitters/ receivers to the matching unit (Tad): 2 x 1 mm² copper cable. UM71 Typical Application Maintenance Ansaldo STS France also offers tools for the workshop or field maintenance of UM 71 products. Certification The whole range of UM 71 track circuit complies with the EN standard. 2

Characteristics Transmitter: 3 modules N.S1.

Receiver: 2 modules N.S1. Supply: 24 V CC (22.5 to 28.6 V) Load current: 0.

inductor (SVac): Installed at the center of the track. Module buried in the ballast.

Tuning unit (BA): Fixed to a post alongside the track in a shock-proof and All equipments work

5 Characteristics Transmitter: 3 modules N.S1. Supply: 24 V DC (22,5 V to 28,6 V) Load current: 1,1 to 2,2 Amp depending on the application Receiver: 2 modules N.S1. Supply: 24 V CC (22.5 to 28.6 V) Load current: 0.25 Amp Matching unit (Tad): Fixed to a post alongside the track in a shock-proof and weather-proof case. Air-core inductor (SVa): Fixed to a post alongside the track in a shock-proof and weather-proof case. Air-core inductor (SVac): Installed at the center of the track. Module buried in the ballast. Tuning unit (BU): Installed at the center of the track. Module buried in the ballast. Tuning unit (BA): Fixed to a post alongside the track in a shock-proof and weather-proof case. All equipments work in a temperature range of C. References More than track circuits in service throughout the world : Algeria, Australia, Argentina, Belgium, China, France, Korea, Morocco, Portugal, Tunisia. Technical features subject to variation without notice. 3

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10 Ansaldo STS SpA Via Paolo Mantovani Genoa Italy

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