• • • RAIL INDUSTRY • • •
Requirements for outdoor railway trackside cabinets for electronic systems
For railway systems, absolute safety and reliability are of utmost importance as failure in sensitive equipment can have catastrophic consequences, says Alan Vincent, sales director at Foremost Electronics
level crossings. These cabinets protect electronic systems for trackside and signalling applications, radio-based train control systems, and the measurement and evaluation electronics of safety systems on high-speed railway lines, such as axle counters or temperature detection on the train wheels. Today, more and more electronics can also be
T
found on the platform including passenger information systems and comprehensive video surveillance providing information and security.
Requirements and challenges Trains traveling at speeds of up to 300 km/h can cause high wind speeds and vibrations. In addition, outdoor cabinets are exposed to a wide variety of environmental influences such as heat, cold, humidity, dust, and vandalism. In addition, compliance to international standards regarding mechanical stability, special railway standards and certifications must also be observed such as shock, vibration, and EMC protection. Relevant certifications and standards to be met include:
his level of safety must also be provided by electronic cabinets installed outdoors trackside, at train stations, signal boxes, or at
EN 50125-3 For protection against shock and
vibration (1-3 m distance from the track) and wind resistance up to 180 km/h. Specially designed for railway applications and describes the environmental requirements for signalling and telecommunications equipment. These conditions include pressure, temperature, wind, rain, hail, and vibrations and shock events. IEC 61969-3 (EN 1627 and EN 1630) RC2 (old
WK2) for protection against vandalism which defines various resistance classes (RC) in terms of burglary resistance. The individual resistance classes indicate how long a product can withstand the break-in attempt of a perpetrator. A higher class means stronger intrusion protection. EN 1630 describes the corresponding test procedures. EN 50121 For electromagnetic compatibility
specifies limit values and measurement procedures for the interference emission and immunity of electrical and electronic equipment intended for use in railway applications. The specifications are defined for the frequency range of 0 to 400 GHz. A modular design of outdoor cabinet offers a
flexible solution that ensures smooth and reliable operation of sensitive electronics in outdoor locations. While offering a convenient way to
supply a bespoke solution it also provides the ability to be reconfigured if system requirements change. Outdoor modular cabinets add value by
significantly reducing total cost of ownership, operational costs, improving safety, and increasing reliability and service life.
Optimal thermal performance The issue of cooling is of prime importance when installed outdoors. Not only must the power loss of the installed components be dissipated, but daily or seasonal outside temperatures must also be considered. The thermal output of the cabinet must ensure an operating temperature appropriate to the electronics from -40°C to +60°C in an ambient temperature of -40°C to +80°C. Not only does the specified operating
temperature of the electronics and the heating caused by solar radiation play a role here, but so does the heat generated by the internal electronics. Ensuring an operating temperature specified by the manufacturer for the internal electronics ensures reliable operation, extends the service life and operating life of the application. A standard feature of an Outdoor Modular
Cabinet for railway applications is supporting active heat dissipation using a fan kit. Typically, this kit consists of 2 fans with a thermostat, for modified cooling capacity. Using the two integrated 24V DC fans that draw cold air through the doors and blow heated air out through the external top, a thermal simulation provides for a thermal transfer of 160 W/K and an air flow capacity of 540 m³/h. Speed-controlled, air-filtered fans with
thermostats represent an economic and effective means of climate control in cabinets. This active cooling through fans is an open circuit that transports ambient air into the interior of the cabinet to cool the electronics. The air supplied via air-filtered fans must be adapted to the air requirements of the components. Filter mats reliably protect the interior of the cabinet from dust. If air-filtered fans are used at very low outside temperatures, a heating unit may be required in the cabinet. The prerequisite for the use of air- filtered fans is that the ambient temperature is below the maximum possible internal cabinet temperature. As a rule of thumb, a temperature difference of at least 5 K can be assumed. Direct air cooling is extremely reliable and has a long service life with low energy consumption.
26 ELECTRICAL ENGINEERING • MARCH 2022
electricalengineeringmagazine.co.uk
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