Go to page one

The controllers in modern electrical enclosures are based on semi-conductor components. The monitoring elements and control elements used are becoming more and more powerful. The extremely high packing densities result in a higher power loss. The larger the temperature stress of these components, the shorter their service life. Thus, it can lead to overheating, the so-called hotspots and in the
worst case premature failures.

Humidity is another parameter which has to be assessed within the framework of a concept for the thermal management and process cooling of electrical enclosures. In the ambient air there is always a proportion of dissolved water. Depending on the temperature, the air can absorb a larger or smaller amount of water. If the temperature drops e.g. due to day / night change, there is a risk of condensation
building on and between the electronic elements. Corrosion and electronic failures can be a consequence here, too.

 Since 2005 we have started to implement the climate control concept we developed together. In addition to the cooling units, which are predominantly used inside the mountains (ambient temperatures up to +40 °C), Pfannenberg heaters also had to be installed in the portal sector (ambient temperatures to -20 °C).

These heaters ensure that the temperature inside electrical enclosures does not fall below the so-called dew-point. The dew-point is the temperature that moist air has to drop to - by unchanged pressure - so that the amount of water dissolved in the air is precipitated as condensate. At the dew-point, the relative humidity is 100%; that means that the air is saturated with water vapor.

The successful collaboration between both companies is to be continued in form of the new project Gotthard Base Tunnel. In 2006, work was started on a solution for the increased requirements of thermal management and process cooling of electrical enclosures on the basis of the tried and tested concept. For example, the demands on the alternating pressure load with +/- 10 kPa doubled, which made it necessary to completely rework the mechanics of the cooling units. In a Swibox test laboratory developed especially for such projects, the new design and the electrical enclosure proved their functionality - successfully running through 200,000 alternating pressure loads +/- 10 kPa.

 

Controllers ensure system uptime


The integration of the electrical enclosure climate control units into the central tunnel system was a further requirement which had to be implemented. As a result of the integration, there will be the possibility to access all operating data of the cooling unit in the future.

Thus, the current temperature of the electrical enclosure can be read for example, or the hours of operation of the most important main components can be monitored. This is especially important to prevent unplanned failures and downtime and, by planning maintenance works in advance, to guarantee a high level of system uptime.

Pfannenberg's new Generation of Controllers, designed especially for this project, have an Ethernet transmission protocol, and provide a variety of parameters which can now be monitored in the central tunnel control. These heaters ensure that the temperature inside electrical enclosures does not fall below the so-called dew-point. The dew-point is the temperature that moist air has to drop to - by unchanged pressure - so that the amount of water dissolved in the air is precipitated as condensate. At the dew-point, the relative humidity is 100%; that means that the air is saturated with water vapour.

The controllers are not only used directly inside the cooling units. The climate controller was also integrated into 500 other electrical enclosures without a cooling unit. This makes a temperature monitoring system possible, which, like the climate control units, can communicate with the tunnel control system and, if necessary, can be replaced with such, without having to reinstall the data transfer.

 Another first in this development is attention paid to energy efficiency. An intelligent control concept was implemented for this, optimizing the energy efficiency, which is already very good in the active cooling mode, additionally in the passive mode (only the electrical enclosure air is circulated).

Due to the integration of a temperature sensor at the allegedly most critical point inside the electrical enclosure, the internal fan responsible for the circulation of the air in the electrical enclosure is only switched on when a defined limit temperature is exceeded. The cooling unit does not start to cool actively again until a limit temperature is exceeded despite the circulation of the air. This control concept helps to reduce the energy consumption further, since all active components are switched off in the event of the energy saving
mode described above.

 Another important point is that the uptime of the units is guaranteed to last for 10 years after the initial operation of the tunnel in 2016. This results in the increased demands to maintenance friendliness. Thus, the MTTR (Mean Time to Repair) has to be as short as possible, this means the time necessary to replace the components quickly and easily in the framework of defined maintenance work.

In 2010 the first cooling units were delivered to the company Swibox. In the meantime, all units have been delivered and will be installed one by one, together with the electrical enclosures, in the 176 cross passages of the Gotthard Base Tunnel. They have already been able to prove their reliability every day, as the various test phases started a while ago and will continue until the start of the scheduled railway operation on 2016.

 


© 2012 Pfannenberg Incorporated | 716.685.6866