Light Rail (Tram) Switch Point
"Complete Solution for Light Rail Switch Point "

Switch Machine
Electronic Operational and Control System
And Vehicle Equipment

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Light Rail Switch Point System - General Introduction

Now that light rail transport is again becoming popular in many cities around Europe and the world, transit authorities face the issue of how to control tram switch points and how to ensure they do not switch when they are not required to do so.

Increasing demands are being made on the attention of drivers, who must focus on the traffic around them and on the needs of passengers. Transit authorities, therefore, must compensate for these demands by equipping vehicles and track systems with high-quality automated equipment which makes the drivers’ work easier and more pleasant.

As far as control systems for the switching/securing of points are concerned, the following facts should to be taken into account:

1. The control of tram switch points in cities, the assessment of each particular traffic situation, and the decision about entering the switch point area must remain within the competence and responsibility of the driver. This type of operation is called “sight distance driving” and represents a completely different operation and different method of ensuring safety as compared with the railway, for example.
   
   
2. It is in the interests of both transit authorities and drivers to use equipment that makes the drivers’ decisions as easy as possible. The equipment should provide drivers with accurate and clear information to assist them in making correct decisions, and to guard against any potential hazard or accident.

There are no worldwide regulations / standards capable of systematically solving issues connected with “sight distance driving”. Essential and very detailed material is available only from the German Union of Transport Enterprises, which provides an assessment of risks based on European standards and a subsequent determination of parameters for equipment controlling tram switch points and their method of operation. This has resulted in the regulations and recommendations of VDV No: 343, 331, etc. Customers worldwide refer to these regulations, insofar as they define a safety and technical standard for equipment they intend to purchase.

It follows from the above that the control of switch point equipment as a whole (i.e., with motor drive, locks and control system) has to comply with the following requirements:

1. The provision of VDV regarding “sight distance driving” with respect to traffic safety, design and circuit solution for specific transport conditions (for example speed).
   
   
2. The requirements of the operator regarding the possibility of control with respect to currently operated equipment and with a view to future operation.
   
   
3. The requirements of the operator regarding additional equipment functions (tram priorities at intersections) and acquiring additional information for use by the operator.

It is clear from the above that we are talking about complicated and important equipment that is in constant operation under every kind of environmental condition. It is necessary that the operator should be capable of maintaining the equipment in good technical condition and that they check the condition of the equipment regularly.

Our TMPKM control system complies with the requirements specified under Item 1, i.e., with the provisions of VDV regarding “sight distance driving” with respect to traffic safety, design and circuit solutions for given operating conditions. The development and the verification of individual components have been carried out in cooperation with our German partner, BBR Company, the leading supplier of this equipment in Germany. Eight years of cooperation with BBR has resulted in solutions used in hundreds of applications with not a single example of any safety-related failure.

The requirements specified under items 2 and 3 are capable of variation and can be adapted to specific conditions based on individual agreements with each customer. Our longterm cooperation with customers worldwide documents our achievements in finding tailor-made solutions. It also confirms that attention to customers’ needs, consistent customer support and time devoted to the training of customers’ employees brings positive results for the customer. From this point of view, we present our system for the control and securing of tram switch points (TMPKM) as a system capable of further development based on the customer’s requirements. Most importantly, the control system complies with accepted VDV safety standards for “sight distance driving” however it may be modified.

Basic components of the assembly comprising the control system and the switch-points system with drive, include:

Control system:

1. Fuse box
2. Control system in cabinet
3. Signaling lamp
4. Resonant track circuits
5. Radio signal receiver
6. Cable lines
7. Switch point heating

Car equipment:

1. Radiosignal transmitter
2. Switch or button on driver’s panel for giving direction, cables

Switch Machine:

1. Switch-points machine with drive
2. Heavy steel earth box

Control System

Introduction

An assembled unit consists of an electronic control system located in an enclosure next to the tram rails, together with a switch with a drive installed in the track. This unit performs all the functions required for the safe electric switching of tram points and for signaling, including the reporting and recording of important operating and failure conditions. The control system also ensures the regulated heating of the switch points. The system may be powered from the trolley line (for example 600 or 750 V DC) or from any common distribution network (AC). Connection from other networks is also possible, depending on the customer’s requirements and on the type of electro-hydraulic points drive used.

To simplify matters, we are going to describe only the system supplied from 600 V or 750 V DC traction line.

The system has to perform the following functions:

1. Reliable and simple switching of points.
   
   
2. Securing points against unwanted switching and other hazardous operational conditions in accordance with the applicable regulations (IEC 65 A [Sec] 123, VDV and DIN regulations, V VDE 0801 and BOStrab regulation Section 17, etc.) and in accordance with the customer’s conditions (for example for speeds below 15 km/h or over 15 km/h).
   
   
3. Protection of the tongues of the switch points against damage.

Description of Functionality

1. Switching Command
   During normal operation, the system (i.e., the switch) is controlled by a command from the tram.

   The command for switching the points in the required direction is issued from the tram to the control system using an encrypted radio signal. Trams are equipped with transmitters mounted on the right front wing of the vehicle. The points systems have receivers in the ground on their right side (with respect to the direction of travel). This method enables drivers to set the required direction either manually pressing a button – or with fully automated points switching by means of the on-board computer of the tram, provided the tram is equipped with such computer, and the computer has information about the tram’s position in the city.

   The signal from the tram points can also be utilized for other purposes, for example: Monitoring the movement of trams in the city; organizing traffic in the depot; and, enabling adjustment of tram priorities in the traffic signaling mode.

   The system can be adapted to any known method of points switching presently utilized, or points can be switched manually using a track switching bar. Electrical switching is disengaged for safety reasons while manual switching is taking place. The insertion of the track switching bar into the switch points machine is automatically registered by an inductive sensor.

   The system may be modified to control and secure more than one sequentially located switch points with a single command.
   
   

2. Blocking against unwanted switching
   The points are immediately blocked by the microprocessor control unit after the switching of points or after the crossing of a switching point receiver when no change of position is required.

   The second additional blocking independent of the functionality of the tram and of the work of the tram driver (pursuant to IEC 65 A (Sec) 123, VDV and DIN V VDE 0801 regulations and BOStrab regulation, Section 17, etc.), is achieved by rail blocking resonant circuits located both in front of and behind each set of points. Further electrical switching of points is possible only after the tram has passed through the entire monitored area and after the second blocking circuit has been unblocked. This “Switch Point Blocked” condition is signaled by a flashing symbol throughout the period that the switch point is blocked.
   
   

3. Switching, locking and inspection of the switch tongues position
   The execution of switching, locking and inspection of the switch tongues’ position is performed by a switch-points machine with drive located in the track between the rails. This switch-points machine is designed to guarantee reliable points operation even under very heavy operating conditions and with minimum maintenance. The motion of the drives is transmitted to the tongues via the main draw bar. Once the tongues reach the end position, the draw bar is locked in position. The control draw bar, located 20 cm from the tip of the tongue, is drawn to the end position by the drive. Should the tip of the tongue fail to switch properly, and should any gap larger than that determined by the points design supplier (usually 2 mm) occur between the stock rail and the tongue (for example, due to the presence of a foreign object in the points) this situation is signaled to the control system by the control draw bar position sensor and the failure is displayed on the signaling lamp. A dot is displayed on the signal lamp instead of the required direction. A special directive determines the actions drivers should take in such a situation. The same method is used to detect the main draw bar position and the proper operation of the main draw bar lock.

   All the functions are preserved in the event of manual switching with a track switch bar. Once the track switch bar is inserted into the slot of the switch-points machine, the system is automatically blocked and it is not possible to switch it with any other command.

   All operations of the track switch control system are recorded into the memory module of the control cabinet and can be displayed as below for analysis, troubleshooting, and accident investigation.
   
   

   

Description of Individual Components

Fuse Box
A lockable box is mounted on a pole at a height of approximately two meters. It enables the system connection to the trolley line. It contains a fuse switch isolator with a fuse for power circuit protection. The cylindrical fuse for voltage of 750 V DC and for current of 20 A has the breaking capacity of 15 kA. The isolator enables safe disconnection from the supply voltage in the event of maintenance or equipment repairs.

Control System in Cabinet
The control box is a cabinet located at the ground level mounted on a base. Cables to the cabinet lead through its base from under the ground. The cabinet with the control system contains power circuits with contactors for the switch-points machine and for points heating, as well as their required control circuits. Power for the control circuits is obtained from the integral inverter with 400 - 900VDC input, 24 VDC output. Control circuits are comprised of individual replaceable modules (plug-in boards with connectors) located in a supplementary box. The following modules are used in the standard version of the control system:

1. Radio signal decoder
2. Microprocessor control unit
3. Output relay unit
4. Memory unit
5. Points heating regulation unit
6. Rail security circuit unit

Functions are managed and controlled by microprocessors. Inputs and outputs from the control microprocessor are also permanently monitored. Should any failure occur which might endanger the safety of the operation, the electric points switching is deactivated. A memory unit is installed, enabling the storage of operational information for several weeks (or a longer period of time if so required by the customer). In the testing mode, the system enables on-line data communication between the control system and a central computer over a standard interface and using a discretionary data transfer medium. Data access is also possible using a portable PC. The memory board may also be easily removed and replaced with another one. Data access is then performed using a computer either in the field or in the maintenance facility. The control box also houses circuits enabling communication with traffic signaling equipment for traffic prioritization, and supplies up to 4 KW for heating rods for points heating.

Signaling Lamp
The lamp is normally manufactured from fiberglass and can be installed either on a pole or hung on a transverse rope. Lamp symbols are made from high-luminescent LED diodes with a long service life. Diode colors available are red, yellow or blue and it is also possible to supply a lamp with customized shape and color according to the customer’s local regulations. The lamp is supplied by 24 VDC from the control box. Other types of signaling lamp can also be used.

Rail Resonant Circuit
The rail resonant circuit identifies when rail traffic is over the points. The circuit consists of a delimited zone of rails (inductance) with a condenser located in the center which divides the zone into two loops tuned to a common resonant frequency.

The circuit requires transverse insulation of rails in the specified zone (max. 12 meters) but does not require insulation of lengthwise rail contacts. Large metallic objects must not be located in the delimited zone as these would negatively influence the electromagnetic properties of the circuit and reduce its sensitivity. The circuit responds to a rail-to-rail short circuit caused by the tram axles and subsequently, in the second operating mode, to the metallic mass. The circuit is controlled by the “WSK” microprocessor module located in the control box. This module also automatically adjusts the operating mode of the track circuit depending on external changes (humidity, rain, snow, salt etc.). Two track circuits are usually used to secure a single set of points. One circuit is usually located in front of the points (at a distance of approximately 12 meters) while the other is located behind the points.

Radio Receiver and Transmitter
The receiver is located in the ground (next to the rail) in a small enclosure. It receives coded signals from transmitter(s) installed in the tram(s) communicated over a limited range of approximately two meters. The trackside control box then receives information about the points switching request and tram identification data.
 

Receiver:	Transmitter:

Earth box for radio signal - receiver at the outer side of the rail

Cable Lines
Input lines to the control system lead from the trolley line over the supporting system to the fuse box located on a pole and then through the ground to the control box. The cable is protected using conduit. The power circuits utilize cable with insulation designed for a minimum voltage of 1000 V.

Points Heating
Heating rods with a power input of 300 W per meter of length are used for points heating. The rod length is selected according to the type of points used. Rods are inserted into stainless pipes located, for example, under the rail head within the area of the points. The replacement of the heating rods is possible after opening a metal cabinet attached to the rails at the point of connection. Power is supplied from the trolley line and each heating rod is connected via its own cable to the control cabinet. Protection is ensured by a 2A or 4A fuse (separately for each heated set of points) located in the control cabinet. Switch point heating is controlled by the "TREG" module within the control cabinet.

The temperature sensor is installed on the rail in one of the heating rod cabinets. Other sensors are located at convenient points.

Car Equipment
Position of radio-transmitter on the streetcar

Switch-Point Machine with Drive
The light rail switch point system uses a switch machine and checking pull rods VSP-1-K. This unit is designed for mechanized or manual resetting of turnouts with spring blades into the desired direction. The VSP-1-K is controlled by means of a particular system of electric control turnouts. The system may be fed by 600 - 750 V DC (with electromagnet) or by 120 V AC (with motor and hydraulic).

The VSP-1-K points system secures:

• Thrust of the setting rod into both extreme positions
• Locking of the setting rod in both extreme positions
• Signaling of the locked setting and checking rods
• Locking of both checking rods in both extreme positions
• Signaling of both extreme positions of both checking rods
• Signaling that the track switch bar is in the setting pocket
• Deformation free forced resetting (bursting)

Technical Data

Example with VSP-1-K switch machine:

Summary

Over 300 systems have been installed and commissioned in various European cities. There are several variations of these systems adapted to customers’ requirements that operate in different operating and climatic conditions. As service and spare parts supply are ensured exclusively by our company, we are immediately informed about any failure. We provide training and hands-on practice for our customers, who are then authorized to carry out routine repairs and maintenance of the systems. We have sufficient direct information from our customers to know the equipment is reliable, requires minimal maintenance and is reasonable in price.

Also, very important for customers, is the exceptional variability and ability to adapt to the existing condition of similar devices owned by the customer, and the possibility of a gradual overall system improvement in the course of preserving normal operation in the city.

Further details can be obtained from the contact address below.