Safety, Standards & Regulation, Signalling & Communications

Safety at high voltage

How one company is making for safer electronic handling.

To enable reliable transportation of passengers and goods worldwide, trains are typically tested thoroughly before they join the international rail network. That’s why the Bombardier Group carries out functional and electrical tests on its trains on its test rigs at its site in Bruges, Belgium. To ensure safe operation at high voltage, the automation expert Pilz developed a safety concept based on its PSS 4000 automation system.

For the electrical test, the completed trains are moved by rail to the test rig. This resembles an oversized cage, as it is secured all-round by massive fences to protect against unauthorised access. The tests themselves need to be thorough, as literally every wire is tested – that’s more than 5000 connection points in one vehicle.

Marc Wuidart, facility manager at Bombardier, is well acquainted with the testing procedure.

“In the first cage we test the quality of the wiring and use dielectric tests to check the insulation,” Wuidart said.

“The train then passes to the next test cage for function tests.

“These range from safety checks that cover the thickness of the air ducts and pneumatic brake tests through to the air conditioning and heating – even the high voltage inverter is tested at 220V and 380V.

“Working under high voltage always requires a special procedure to guarantee staff safety.”

A well-rehearsed team

The internal technical service at Bombardier guarantees that all its plant is ready for operation. When installing new plant the train manufacturer works with SPIE, an international technical service provider for buildings, plant and infrastructure.

“In this project we were responsible for the technical development of the test rigs,” said SPIE site manager Hans Soulliaert.

“Our speciality lies in implementing the mechanical and electrical aspects of the plant; for safety issues we relied upon the expertise of Pilz.

“The result of this symbiosis was a plant with an increased level of safety. The fact that Bombardier, SPIE and Pilz had worked together previously was an advantage.”

Step-by-step approach to the safety concept

Safety experts at Pilz took on all the tasks regarding calculations, programming, validation and concept development.

The company took a step-by-step approach: firstly, risks were identified and evaluated as part of the risk assessment. Then they worked with the customer to develop practicable, compliant solutions for the safety concept.

This forms the basis on which the safety design takes shape. Once the detailed engineering was complete, SPIE continued with the practical implementation. SPIE was responsible for the mechanical and electrical installation of the various components. Finally, Pilz validated the whole process.

“Then every component was inspected step-by-step, using a shutdown matrix,” said Kwinten Cantraine, sales manager for Flanders at Pilz Belgium. “This verifies once again that everything is working technically and will shut down as intended in a worst-case scenario. This validation process is a very important step that is sometimes overlooked.”

High voltage behind bars

Guards are an essential part of the safety concept, making test operations in high voltage test rigs safer. Previously all staff were able to move freely around the test site. That’s why the test rig was closed off with a fence.

Today, flashing lights make clear when the high voltage is active. Benoit Sioen, safety engineer at Pilz, explained another aspect of the safety concept.

“As it’s a large work area with no overall view, we introduced a reset procedure,” Sioen said.

“Before starting, a mandatory test must be carried out to activate three reset buttons: one at ground level, one above that and one in the pit. This prevents anyone remaining in the danger zone unnoticed and being overlooked when the power is switched on.”

Protective measures are effective

The company also introduced an access control system to the test cage with RFID identification. Now only authorised personnel can access the test cage and the plant can only be started when a uniquely coded key is inserted. As soon as an emergency stop is triggered, power is removed from the whole cage. The same happens if any gates are opened without authorisation; this is monitored using the coded safety switch PSENcode from Pilz.

Staff at the control cabinet can immediately check the status of the emergency stops and safety gates. This enables rapid diagnostics and reduces downtimes on the test operation.

One system monitors both test cages

All safety I/Os are controlled via the automation system PSS 4000. One PLC is used for two test cages. A PLC is positioned in the first test cage and an I/O module in the second. Both are connected via the real-time Ethernet SafetyNet p.

So, there’s one program that controls two test cages. Within PSS 4000, function blocks can be tested separately and stored in a library via the software platform PAS4000.

New function blocks can build on existing ones but have their own specific parameters. This makes it so much quicker to write a second, similar program, saving a great deal of programming time. Increased safety level Bombardier is very happy with the increased safety level on the test cages. The test manager has a better view of all the functions.

“The test manager can now stop the process himself, to carry out certain checks and to prevent unsafe situations,” Marc Wuidart said.

“However, safety is a continuous process in which we will keep investing. We are delighted that Pilz can support us with this.

“We will happily count on Pilz again.”

Final comments

While in this particular application the PSS4000 automation based safety PLC was used to meet the needs of the customer, Pilz also has a CENELEC certified version of this PLC called the PSS4000-R which has been developed for use in rail applications that require a higher level of certifications. With the automation system PSS 4000-R, Pilz offer a proven, safe and tested system for tailored and particularly economical solutions for rail.

The “R” in the product names indicates that these products were developed specifically for railway applications. They conform to SIL 4 in accordance with the following CENELEC standards: EN 50121, EN 50126, EN 50128, EN 50129, EN 50155 and EN 45545. Their modular design makes them eminently suitable for digital control tasks and retrofitting. 

The automation system PSS 4000-R is a more affordable solution than the proprietary control solutions often used in the railway sector, both in terms of procurement and maintenance. 

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