Brake and Wheel Slide Protection Testing for Trains at Velim Test Center

Velim, a small village of just 2,000 inhabitants in the Central Bohemian Region, is home to one of Europe’s largest train test centers. Here, 40 kilometers East of Prague, the Railway Research Institute, Výzkumný Ústav Železniční, a.s. (VUZ), operates unique testing and technology facilities.

VUZ test center Velim

VUZ blends modern industrial design with high-tech functionality. The facility is in a rural setting, combining natural and engineered landscapes. However, the expansive test tracks and the clean lines of the buildings emphasize practical use and durability.

Overall, the VUZ testing facilities have state-of-the-art technology and expert staff. Our facilities are renowned for their comprehensive capabilities, which serve a wide range of testing and certification needs in the railway industry. 

We support the development of railway vehicles and components, ensuring their safety, reliability, and compliance with international standards. Key features of our test facility include:

• A sizable auxiliary yard, 

• Four halls for preparing and testing, and 

• A power supply station with standard European power systems: AC 25 kV/50 Hz, AC 15 kV/16.7 Hz, and DC from 750 V to 3 kV. 

The facility also features two testing circuits: 

1. An extensive circuit with a 13.276 km track, capable of reaching a maximum speed of up to 230 km/h, and 

2. A smaller one with a 3.951 km track, capable of reaching a maximum speed of up to 115 km/h. Figure 1 illustrates the facility layout.

The VUZ testing laboratory

The VUZ Testing Laboratory (ZL VUZ) has accreditation according to EN 17025 for testing railway vehicles, their components, and railway systems. The ZL VUZ includes:

• Dynamic Testing Laboratory: equipped for evaluating the dynamic performance of railway vehicles, including their ride quality, stability, and behavior under various operational conditions;

• Mechanics testing department: brake system tests, derailment safety tests, hygiene tests, including noise, lighting, and door measurements;

• Electromechanics testing department: EMC tests with track circuits and axle counters, measurement of external electromagnetic fields, impedance measurements of railway vehicles, traction tests, tests of electrical power supply systems, tests of current collectors.

Since 2010, we have adopted Dewesoft measuring systems at the VUZ Testing laboratory. The first devices were the mini dynamic datalogger, the MINITAUR , and the USB data acquisition system, DEWE-43A, which could register 16 channels. Since then, we have purposefully expanded the measurement base to register up to 80 Dewesoft quantities.

We now use the rugged and distributed EtherCAT data acquisition system modules, KRYPTON, and the SIRIUS modular data acquisition system for most tests. 

Thanks to their variability, the measurement systems enable our engineers to measure on a single freight wagon, including the automatic start and stop of recording, as well as trains with complete sets of multiple rail units.

Brake testing a multiple-unit electric train 

The Testing Laboratory at VUZ performs comprehensive testing of brakes and wheel slide protection devices by simulating real-world conditions on specialized test tracks. These tests are among the most complete tests at the Testing laboratory. 

The tests involve meticulous preparation, controlled execution, and detailed data analysis to ensure that Braking Systems and Wheel Slide Protection Devices (WSPs) meet stringent safety and performance standards. Our elaborate facilities, equipment, and expertise ensure that all tests are conducted with precision, providing valuable insights into the effectiveness and reliability of these critical railway components.

Measurement setup

For testing the brake systems of an electric multiple unit train, our engineers use the following setup:

Data acquisition system

• 1x SIRIUSi-8×LV: an eight-channel isolated SIRIUS slice for Low Voltage, Full Bridge, CAN, and USB2 interfaces.

• 2x KRYPTONi-1xSTG: single-channel rugged and distributed EtherCAT data acquisition system with complete isolation for Voltage, Strain, Potentiometer measurements.

• 9x KRYPTON-4xSTG: a rugged and distributed EtherCAT data acquisition system, three-channel differential slice for Voltage, Strain, Potentiometer measurements.

• 1x KRYPTONi-1xCAN: a rugged and distributed EtherCAT data acquisition system, single-channel isolated module for CAN

• 1x ECAT-SYNC-JUNCTION: synchronization slice for KRYPtON EtherCAT and SIRIUS USB devices.

• 1x DS-VGPS-HSC: 100 Hz GPS-based position, speed, and displacement sensor.

Sensors

• Pneumatic pressure sensors

• Accelerometer

• Temperature sensors

Software

• DewesoftX data acquisition and signal processing software

SIRIUS is a versatile and robust data acquisition system that provides high-end signal conditioning amplifiers for nearly any signal and sensor. SIRIUS offers a high dynamic range (160 dB) and galvanic isolation and is available in USB or EtherCAT® configurations.

KRYPTON is a rugged and distributed EtherCAT data acquisition system for field measurement in extreme and harsh environments. The device's operating temperature range is from -40°C to +85°C, offering high 100G shock protection. It features an IP67 degree of protection, operates within an extreme temperature range of -40°C to +85°C, and provides high 100G shock protection.

The DS-VGPS-HSC combines a highly dynamic GPS-based speed sensor and a synchronized time base generator. The combination enables the complete, synchronized acquisition of data from multiple systems, both inside and outside, moving vehicles. The portable and rugged system measures position, speed, and displacement, providing synchronized data acquisition and real-time speed measurement. 

The DewesoftX software, which records and monitors measurements, offers advanced data recording, analysis, visualization, and reporting features.

The types of testing

Braking tests on railway vehicles consist of three main parts:

1. Stationary tests to determine the parameters of the braking system, 

2. Dynamic tests to assess the braking effect, and 

3. Wheel slide protection tests to check the correct functioning of the wheel slide protection device.

The vehicles tested include freight wagons, passenger coaches (both single and multiple units), locomotives, as well as electric and diesel-powered units. The size of the data acquisition system and the number of sensors we use for testing depend on the vehicle under test. 

Before the test begins, we prepare a test specification. This test specification includes a list of measurement quantities, a list of used sensors, and a test program. 

We prepare our vehicle in a dedicated test preparation hall, conduct static tests in an auxiliary yard, and perform dynamic and wheel slide tests on our large test circuit.

During the brake tests, we monitor pressures in specified areas of the brake system, including the main reservoir pipe and the brake pipe, as well as control pressures to the brake distributors and the brake cylinders. We also measure acceleration, vehicle speed, distance, and brake disc temperatures. 

Static tests

We conduct stationary brake tests to verify the essential characteristics of the braking system and ensure that its components function correctly and safely.

Using the control systems from the driver’s cabin, we apply the train's brakes entirely. The static tests involve braking with different systems, including emergency braking with and without magnetic braking, electro-pneumatic braking, and various types of service braking.

From the measured waveforms of the brake system quantities, we subsequently determine the filling and release times of the brake cylinders and the maximum pressures achieved for different types of braking (emergency, service, etc.). We also verify that the overall functioning of the compressor and braking system is correct.

After measuring, we analyze the results, enter the evaluated values of the measured quantities into tables, and prepare a test report.

Dynamic tests

Next is a dynamic brake test. In the dynamic brake test on trains, we evaluate the braking system's performance under actual operating conditions, where the train is in motion. 

We use dynamic tests to determine the braking performance of the moving railway vehicle and to check the capability of the emergency braking systems to stop the train. The basic principle is determining the braking percentage based on the measured stopping distance for a specified speed.

We drive the vehicle at a specified speed and subject it to controlled braking maneuvers. The testing procedure can involve full stops from various speeds and applying different braking systems, such as emergency braking with and without magnetic braking, braking with electro-pneumatic braking, and other types of service braking.

We collect data in real-time to record the braking system's performance during the braking tests. The data acquisition includes measuring deceleration rates, braking distances, and brake force distribution.

Our engineers then analyze the collected data to assess the braking system's performance. They evaluate key metrics, including braking distance, brake force consistency, and temperature rise in brake components.

Wheel slide protection tests

The Wheel Slide Protection (WSP) system tests are part of the dynamic tests that verify the correct functioning of the brakes. The WSP device prevents wheel slip and lockup during braking, especially under low rail adhesion conditions.

We connect special speed sensors to the measuring system via CAN bus to test the wheel slide protection device. The primary function of the speed sensor is to detect the signals generated by the rotation of the phonic wheel, which we have mounted on the axle end. 

Through these sensors, we monitor the speed of each axle of the testing vehicle, the operation of the electro-pneumatic valves, and, if necessary, the braking force of the electrodynamic brakes.

We install and calibrate WSP devices on the vehicle. The sensor setup is similar to that used in brake tests. The sensors enable continuous monitoring of wheel rotational speed, brake force, and other relevant parameters.

We then simulate conditions where WSP devices would be critical. Pouring soap solution under the vehicle's wheels during braking simulates low wheel and rail adhesion. To induce wheel slip, we subject the vehicle to various braking scenarios, including sudden stops, rapid deceleration, and braking on surfaces with varying adhesion.

The tests evaluate the instantaneous speeds of the individual axles and the status of the relevant WSP valves, including any WSP outputs to the train's overriding control system, e.g., for blocking doors, activating the electromagnetic rail brake, and the initial value of the adhesion coefficient.

The measurement and evaluation system enables us to determine the validity of the individual test immediately after the vehicle stops, as well as to consider possible measures, such as adjusting the solution concentration used to reduce the adhesion coefficient.

Standards and implementation documents

We work with international and European standards, as well as the national notified technical rules of the countries where the vehicle under test will operate.

The essential documents for the tests are the European Union documents, Technical Specifications for Interoperability (TSI). The TSIs define the technical and operational standards that each subsystem or part of the subsystem must meet to ensure the interoperability of the European Union's railway system. We work with the UIC leaflets, Locomotives and Passengers TSI, and the Freight Wagons TSI.

The international standards include those from UIC, the International Union of Railways, which has developed the “UIC code”. The code comprises UIC leaflets defining standard rules to ensure safety and efficiency in railway system design, construction, operation, and maintenance. 

We use, for example:

• UIC 544-1 defines braking performance and describes the method for determining the braking performance of railway vehicles and trains. 

• UIC 541-05 specifies the construction of various brake parts, including WSP devices. 

Other European standards we apply are:

• EN 14033 defines the technical railway requirements for running machines and other vehicles used in the construction, maintenance, and inspection of tracks, structures, track formations, and fixed electric traction equipment. 

• EN 16834 defines a harmonized method for assessing braking performance by testing locomotives, passenger coaches, freight wagons, and self-propelled passenger trains.

• EN 1559 specifies the criteria for system acceptance and type approval of a wheel slide protection (WSP) system.

• EN 15595:2018+A1:2023 specifies the criteria for system acceptance and type approval of a wheel slide protection (WSP) system.

We can also mention Notified National Technical Rules (NNTRs), such as vehicle tests for countries including Czechia, Slovakia, Germany, the United Kingdom, Estonia, Latvia, Austria, and Spain.

Conclusion

The low rumble of trains is audible near the village of Velim, where our specialized testing, evaluation, and certification of railway components ensure the safe and reliable operation of railway vehicles and infrastructure. 

By providing real-world data and rigorous testing conditions, we support innovation and help manufacturers meet international standards, thereby enhancing the performance, safety, and longevity of railway systems.

We appreciate the modularity of the Dewesoft measuring system, which allows us to optimize the measuring chain according to the type of vehicles we test. We also value its robustness and durability. We installed Krypton measuring modules on the underside of freight wagons for several weeks. Such exposure to temperature fluctuations, dust, and shocks has proven the Dewesoft system suitable for testing in heavy railway traffic.