IABG certification for earthquake safety in the maximum danger zone
An individual configurable UC-HE cabinet system by BENNING
The need to consider earthquake risks is almost everywhere. Currently, more than 2.7 billion people live in an earthquake-prone area. If you take a look at the earthquake zone map, you will see that many densely populated cities such as Los Angeles, Shanghai, Tokyo, Lima or Istanbul are located in seismogenic zones. In this case, we are talking about Category 4 hazard zones, based on US UBC standard classification. If a major earthquake occurs in one of these regions, it can cause severe damage to buildings, infrastructure or technical plant - affecting, among other things, transport, industry, healthcare system or energy supply.
Seismic verification, vibration test and certification by IABG
On average, large earthquakes with a magnitude of 6.0 and higher occur about three times a week - nearly 100 earthquakes a year cause structural damage, according to recent statistics from the National Earthquake Information Centre (NEIC). This unpredictability makes it necessary to protect electrical equipment by using UPS systems for bridging any power outages and network failures, for example.
But how are the UPS and power plants protected against the impact of an earthquake?
Highest safety standards
The highest safety standards must be met, although a classification into different priority levels is also necessary. The failure of the telecommunications system, for example, poses a much lower risk than a blackout of the pump system that supplies the cooling circuits.
In order to meet the variety of high demands, BENNING has developed an individually configurable cabinet system that can be perfectly adapted to the different earthquake categories and safety requirements. It is available in the following versions: UC (Standard), UC-LE (Light Earthquake Resistant), UC-ME (Middle Earthquake Resistant) and UC-HE (Heavy Earthquake Resistant).
In comparison to conventional designs that seek to achieve the necessary earthquake resistance of housing through high rigidity, the new UC cabinet variants are characterised by a cutting-edge approach. This approach and the use of high strength steel allow a structure to perform well-defined movements without weakening the cabinet system. A construction method that has also found its way into the automotive sector, for example.
Specific simulation options
The cabinet system development process has also changed. The method used in the past was to first produce drawn constructions as test objects and then to expose them to extensive tests. If the expected assumptions were not confirmed, the engineers would repeat the process chain (Design > Construction > Tests) until the target was achieved.
An integral part of the state-of-the-art construction processes at BENNING, however, is computer-aided development with specific simulation options, which are carried out before the actual hardware tests. This makes the development process significantly shorter and more efficient.
BENNING has also developed a simulation tool which can determine the cabinet requirements prior to the construction stage in order to select a suitable cabinet.
Finite element method
Computer-aided simulations are used to check the load limits using structural and dynamic calculations based on the finite element method (FEM). This results in a standard-compliant analysis and calculation of the deformations or stresses of a cabinet frame during the construction. In addition, physical properties of the cabinet system can be visualised, and potential weaknesses can be precisely located for targeted optimisation measures.
Stringent requirements fulfilled
The construction of a test housing and the verification of the calculations in the company's own environmental laboratory do not take place until the simulation process has been successfully completed. Here, so-called vibrating tables are used, which mimic the vibrations and shock loads caused by an earthquake.
In addition to its own test results, BENNING has had the current UC-HE cabinet design certified by a recognised testing laboratory, the IABG (Industrieanlagen- Betriebsgesellschaft mbH), with the result that this construction exceeds all normative requirements in terms of earthquake resistance, even in the worst-case scenario.
Another decisive advantage arises from the fact that all four cabinet system versions developed by BENNING are based on the same design principle. Suppose, for example, that in earthquake zone 2, a rectifier system in UC-ME design is used to secure the telecommunications system. At the same time, the rectifier system, which supplies the pumps of the internal cooling circuit, ensures maximum safety and therefore chooses an housing certified to the highest earthquake categories for this area. In this way, both power supply systems used are provided with the optimal protection that complies with the cost-efficiency and safety requirements. On the other hand, this provides for easy and quick maintenance because the base frame of the cabinet construction as well as the arrangement of the power and functional elements are identical in both systems. The only thing which is different is the system casing, i.e. the enclosure. Due to this technical and functional analogy, a technician can find his/her way around a servicing task faster. This provides the highest level of safety with maximum cost-efficiency.
Seismic switchgear terminology
The damping characteristic of a switching device limits the overall gain that it experiences during resonance. Suppose, for example, that two cabinets are identical in design, assembly, and weight, but one cabinet has a welded structure and the other has a bolted structure. During an earthquake, the structural elements in the bolted housing move relative to each other, causing friction and noise, such that the seismic energy dissipates much faster than in the welded housing. The bolted cabinet will thus dampen the energy faster than the welded one, thus reducing the time required to build up seismic response. The damping properties of a system are indicative of the system's ability to dissipate earthquake energy. Without attenuation, the resonance gain of the equipment increases without resonance. The higher the attenuation factor of the device, the lower its response curves.