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Switch Machine, Electronic Operational and Control System and Vehicle Equipment
 Light rail switch point system - General Introduction
 Now that light rail transport is again becoming popular in many cities around Europe and the world, transport 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 tram drivers, who have to focus on the traffic around them and on the needs of passengers. Transport authorities therefore try to compensate for this by the use of high-quality technical equipment where the nature of the operation allows for this. Vehicles are thus equipped with new automatic information systems and other equipment, which makes the work of drivers easier and more pleasant.
As far as control systems for the switching/securing of points are concerned, the following facts have to be taken into account:
The control of tram switch points in cities, the assessment of each particular traffic situation, and the decision about entering the points area have to remain within the competence and responsibility of the driver. In normal city traffic this responsibility cannot be removed from the driver. This type of operation is called "sight distance driving" and represents a completely different operation and different method of ensuring safety compared with the railway, for example.
II. It is in the interests of both transport authorities and drivers to use equipment that makes the drivers' decisions as easy as possible. It should provide them with accurate and clear information about everything they need to know for them to make a correct decision, and guard against any potential hazard or accident.
There are not worldwide regulations / standards capable of systematically solving issues connected with "sight distance driving". Essential and very detailed material is nowadays 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 mainly to these regulations, insofar as they define a safety and technical standard for equipment they intend to purchase.
The problem with these regulations is that although they are theoretically drawn up to a very high standard, they are only available in German. Translation of these regulations into other languages is difficult because it is hard to find an expert translator familiar with light rail transport.
European standards are also in preparation but are not available at present (IV/2002). The standards should be available in all European languages and they should be based on the above-mentioned VDV regulations.
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 in operation constantly and under every kind of condition. It is necessary that the operator should be capable of maintaining it in good technical condition and checking the condition regularly.
It is also clear that the whole complex of these requirements cannot be included in one promotional offer and that cooperation with customer in specifying each individual case is necessary.
Our TMPKM control system on offer complies in its basic level of equipment 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. Its 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 this cooperation 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 long-term 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 good results on both sides.
From this point of view, we present our system for the control and securing of tram switch points (TMPKM) as an organic 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 is modified.
Basic components of the assembly comprising control system and switch-points system with drive
Control system:
1. Fuse box
2. Control system in a plastic cabinet
3. Signaling lamp
4. Resonant track circuits
5. Radio signal receiver
6. Cable lines
7. A set for points 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 duty steel earth box
Control system
 Introduction
An assembled unit consists of an electronic control system located in a plastic box next to the tram rails, together with a switch with a drive installed in the trackage. This unit performs all the functions required for the safe electric switching of tram points and for signaling, including the registration of important operating and failure conditions. The control system also ensures the regulated heating of points. The system may be connected to the trolley line (for example 600 or 750 V DC) or to 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 points against damage, and extension of their service life
 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 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.
Switching is possible either simultaneously or by trolley contacts (while driving in the power or power-less mode if necessary). In such an event, the system can be adapted to any known method of points switching by the driver depending on local usage. For example, left without power, right with power, or no change without power, switching to the other side with power, etc. However, we do not recommend this method of points control for new tracks as they place high demands on the attention of the drivers, and the installation and maintenance of control contacts on the trolley line, and their reliability is very low. Furthermore, in larger operations the additional power consumption is considerable. For this reason, these systems are not described in detail here.
Points can be switched entirely manually using a points rod if this is necessary. Electrical switching is disengaged for safety reasons whilst hand switching is taking place. The insertion of the points 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 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 only 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 condition is signaled by a flashing symbol throughout the period that the system is blocked. Any information is stored and available in the memory unit.
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 trackage 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 this 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. Only a dot is displayed on the lamp instead of the required direction. A special directive determines the procedure drivers should follow 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. Any such information is stored and available in the memory unit.
All the functions are preserved in the event of manual switching with a rod. Once the points rod 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.
As the mutual links between the individual parts of the system are very close and as the system must and may operate as an integral unit, attention has to be paid to the position and cooperation of all the elements in the trackage to satisfy individual requirements on speed, safety, comfort and reliability of operation.
Description of Individual Components
Fuse Box
A lockable box made of insulating material 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 Plastic Box
The control box is a plastic cabinet located at the ground level on a base made of the same material. Cables to the cabinet lead through its bottom part from the ground. The cabinet with the control system comprises power circuits with contactors for the switch-points machine and for points heating, as well as control circuits. Voltage for the control circuits is obtained from the inverter 400 - 900V DC/24 V. Control circuits comprise individual replaceable units (plug-in boards with connectors) located in a supplementary box. The following units are used in the standard version of the system:
1. "PRIJE" - radio signal decoder
2. "RIVY" - basic processor control unit
3. "RELE" - output relay unit
4. "RVMEM" - memory unit
5. "TREG" - unit for points heating regulation
6. "WSK" (2x) - 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 the central computer over a standard interface and using a discretionary data transfer medium. This modification will be available during 2002 after testing. Data reading is possible with a portable PC during operation immediately. The memory board may also be easily removed and replaced with another one. Reading is then performed using a program on a PC. The control box also comprises separating circuits enabling communication with traffic signaling equipment. The cabinet may supply heating rods for points heating with a maximum power input of 4 kW (both speeding up and opposite running points).
Signaling Lamp
The lamp is normally manufactured from fiberglass. It 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 comprise red, yellow or blue. 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 V SDC voltage from the control box. Other types of signaling lamp can also be used.
Rail Resonant Circuit
The rail resonant circuit is the basic means for traffic securing over the points. This is a resonant circuit comprising a delimited zone of rails (inductance) and a condenser located in the center, which divides this 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. 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 only subsequently, in the second operating mode, to its metallic mass. The functionality of the circuit is controlled by the microprocessor unit "WSK" located in the control box. This unit 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 in a triangle comprising the crossed rails.
Each circuit is connected with the control cabinet by two special protected cables.
Radio Receiver and Transmitter
The receiver is located in the ground (next to the rail) in a solid plastic cabinet. It receives coded signals from low performance transmitters installed in the trams. The control box then receives information about the points switching request and tram identification data. Communication takes place in a limited range of approximately two meters.
The transmitter is located in the tram in such a way for communication with the receiver to be possible.
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| Receiver |
Transmitter |
Earth box for radio signal - receiver at the outer side of the rail
Trolley Switching or Control Contacts
Depending on the method of points switching, one or other contact (current) is used. The design of the contact can be adjusted depending on the requirements of the customer. The circuits for the evaluation of information from contacts are located in the control box. The separation of the power and control circuits is performed by optical elements.
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 by a hard plastic tube on the pole and by a flexible plastic tube in the ground.
Cables from the control box to the switch-points machine, to the track circuits, and to the receiver are led through the ground in flexible plastic tubes.
The power circuits utilize a cable with rubber insulation and with PVC coating designed for a minimum voltage of 1000 V. The control circuits utilize ordinary cables with plastic insulation and the track circuits use flexible protected cables. The radio signal receiver is connected via four-conductor communication cable.
Points Heating
Heating rods with a circular section made of stainless material and with the power input of 300 W per one 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. Each heating rod is connected via its own cable from the control cabinet. Protection is ensured by a 2 or 4A fuse (separately for each heated set of points) located in the control cabinet. Switching controlled by the "TREG" unit depending on rails temperature or on ambient temperature and humidity is made by a contactor.
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
Electro-hydraulic point machine TSH 100 C
Our light rail switch point system uses a switch machine and checking pull rods TSH 100C. This type is designed for mechanized or manual resetting of turnouts with spring blades into the desired direction. It ensures high running safety, is irreproachable from the ecological point of view, and has a long life with minimum maintenance. 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 TSH 100 C 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 of the spanner in the setting pocket
deformation free forced resetting (bursting)
Technical data:
| Gauge |
900 - 1700 mm |
| Stroke |
32 - 75 mm (conntinuously adjustable) |
| Setting force on the rod |
ca.5 kN |
| Moment for the emergency (manual) setting |
150 - 350 Nm |
| Parting force |
cca 13 kN (according to the request of the client) |
| Thrust of the springs |
1.5 - 3.0 (continuously adjustable) |
| Working voltage |
3x400 / 230 V AC (600 - 750 V DC, var. USA) |
| Control voltage |
24 V DC |
| Parting time |
0.6 - 1 s |
| Dimensions of the box |
|
| Height |
200 mm |
| Length |
900 mm |
| Width |
570 mm |
| Length |
685 mmm |
| Weight |
cca 190 kg |
| Service temperature |
-35°C / +60°C |
| insulation |
yes |
Summary:
Over 300 systems corresponding to the description specified above have already been installed and commissioned in various European cities. There are several variants of these systems adapted to customers' requirements, which operate in various operating and climatic conditions. As service and spare parts supply are ensured exclusively by our company, we are immediately informed about any failure, and asked for explanations of some functions or operating conditions. We also provide training and hands-on practice for our customers' employees, who are then authorized to carry out routine repairs and maintenance of our systems. We thus have sufficient direct information from our customers to know that the preference for this equipment by numerous transport companies is not just incidental. The equipment is reliable, requires minimal maintenance and reasonable in price - important factors appreciated by our customers. We have never had any instance of a failure of the system's security elements.
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.
Having long-term experience with the operation of these systems, we are preparing an upgraded version. While utilizing verified and reliable basic elements, the new equipment will be capable of improved on-line communication. Its installation will be easier, it will have better resistance against interference, and there will be fewer demands on cabling. Access to system data will also be easier for customers. Pilot operation of the new equipment commences in 2002.
We would like to thank everyone for their interest in the new equipment. Further details can be obtained from the contact addresses specified above.
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