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InnoTrans 2008: Reliable detection of contact wire ruptures with Sicat CMS by Siemens

Fast and reliable location of defects in overhead contact lines

The Siemens Mobility Division has developed the contactless measuring and monitoring system Sicat CMS (Catenary Monitoring System) for mass transit and mainline services. It continuously monitors overhead contact line systems at critical points along the line such as at level crossings, near stops and in tunnels.

Siemens Mobility has developed the Sicat CMS monitoring device, which continuously monitors the overhead lines and triggers an alarm if a defect is detected. The photo shows an example in which the sensor is mounted on the swing lever of the prototype tension wheel assembly for the HSL Zuid high speed line in the Netherlands.

If a crack is detected, an alarm is triggered immediately and sent to the control center. Ruptures are detected through measurement and evaluation of the position of the swing levers in the automatic tensioning equipment of the overhead contact line system. In addition to the existing overhead contact line protection, the location and type of defect can be determined much more quickly and precisely and, if necessary, substations supplying power can be switched off selectively. Service on the route can thus be resumed much sooner.

If there is any possibility of a hazard, personnel on board trains traveling on the route can be warned and given appropriate instructions in advance. It is also possible to prevent consequential damage being caused, for example, by other vehicles entering the section of track. As a result, Sicat CMS enhances the availability and cost effectiveness of railway lines. The first of these catenary monitoring devices are already in place and being used successfully.

For rail operators, the safety and availability of their installations and equipment have top priority. But economic and technical reasons often prevent essential components of their installations being designed with the redundancy needed to increase availability. This is especially true in the case of overhead contact lines installed above the tracks. Extraneous factors such as fallen trees can rupture contact wires and result in closure of the railway line. Reliable and speedy detection of ruptures is therefore very important in order to offer passengers guaranteed reliable rail service.

Changes in the length of contact wires and catenary wires due to temperature fluctuations are compensated by means of tensioning equipment, often consisting of weights and tension wheel assemblies. The tension wheel assembly ensures that the weight and the pulling force of the overhead contact line remain in a state of equilibrium. Any alteration of the force applied to the contact wire – such as friction forces caused by elongation of the conductors due to fluctuating temperatures, contact wire uplift during train passages, additional loads in the catenary system or ruptures in the contact wire – results in a change in the angle of inclination of the swing lever of the tension wheel assembly. The friction forces created during normal current collection by the train usually change gradually and, in any case, only slightly. In contrast, contact wire ruptures and additional loads lead to major and abrupt changes in the forces being exerted. A strict evaluation of the change in the swing lever's position and of the time when it occurred thus makes it possible to carry out a precise analysis of the events in and around the catenary system.

Sicat CMS from Siemens measures the position of the swing lever on the tension wheel assembly with the help of a position sensor, which works on the basis of magnetic effects (magnetostriction). The sensor is a contactless device and therefore not subject to wear. The accuracy of the entire system is set to 0.1 mm. A permanent magnet is mounted to one side of the movable swing lever near the tension wheel axle. Together with the swing lever of the tension wheel assembly, this magnet moves along a sensor rod. The measured values of the sensor are sent to the sensor station. There is an air gap around 5 mm wide between the rod of the measuring sensor and the permanent magnet which ensures that the sensor does not obstruct the tension wheel assembly. Moreover, external influences such as loose loads or tree branches cannot adversely affect the sensor's measuring results.

For purposes of evaluation, the bandwidth of the position values during the last few seconds is calculated cyclically. If it exceeds a configured value, an alarm is transmitted to the monitoring system. This is an indication that there is a problem in the overhead contact line system. The operator can then react accordingly, such as by asking train drivers to pay closer attention to the situation. As soon as the catenary system settles down again, the difference between the positions at the beginning and end of the movement is checked. If it is small, this means that the catenary has approximately settled back into its original position. The equilibrium of forces has therefore not significantly changed and a rupture in the contact wire can be ruled out with a high degree of probability. A large difference, however, indicates that the catenary system has assumed a new steady-state condition with a different swing lever position and therefore that the equilibrium of forces acting on the wires has changed as well. The monitoring device then sends a high-priority alarm to the control system. Through evaluation of the movement per time unit and an additional comparison with specifically defined limits, it is possible to determine deviations from the normal operating values.

Sicat CMS can be configured for any size of installation. It can monitor either all parts of the entire overhead contact line system or only critical points along the line such as grade crossings, bridges, tunnels and station platforms. The device contributes to condition-related maintenance with fewer personnel.

The control center of the system is linked up via Ethernet, which uses the telecontrol protocol in accordance with the standard IEC 60870-5-104. As a result, Sicat CMS can be integrated easily into an existing Scada system. A special operator workstation in the control center is not needed.

Prototypes have been tested successfully and are now being used on the HSL Zuid high speed line in the Netherlands and the Segovia–Valladolid high speed line in Spain. The first series-produced systems are being installed on the high speed route between Madrid and Valladolid, where installation work started in spring 2008. Seven evaluation stations with a total of 120 sensor stations and 240 sensors detect the condition of the catenaries along this approximately 140-km-long route. The system detects mechanical faults in the overhead line in places that are sensitive for the operator, for instance, at railway stations and at the two 8-km and 29-km-long tunnels San Pedro and Guadarrama.

The Industry Sector (Erlangen, Germany) of Siemens AG is the worldwide leading supplier of production, transportation and building technologies. With integrated hardware and software technologies as well as comprehensive Industry-specific solutions, Siemens increases the productivity and efficiency of its customers in the fields of industry and infrastructure. The Sector consists of six divisions: Building Technologies, Industry Automation, Industry Solutions, Mobility, Drive Technologies and Osram. With around 209,000 employees worldwide Siemens Industry achieved in fiscal 2007 total sales of approximately EUR40 billion (pro forma, unconsolidated).

The Mobility Division (Erlangen, Germany) is the internationally leading provider of transportation and logistics solutions. With its "Complete mobility" approach, the Division is focused on networking the various modes of transportation in order to ensure the efficient transport of people and goods. “Complete mobility” combines the company's competence in operations control systems for railways and traffic control systems for roadways together with solutions for airport logistics, postal automation, traction power supplies and rolling stock for mass transit, regional and mainline services, as well as forward-looking service concepts.

Siemens AG
Corporate Communications and Government Affairs
Wittelsbacherplatz 2, 80333 Munich
Reference number: IMO200809.050e fp

Franz-Ferdinand Friese | Siemens Mobility
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