Rittal Backgrounder: Is this switchgear system earthquake-resistant?

08.12.2017. Designing switchgear installations for areas that are prone to earthquakes can pose a real challenge to plant engineers. Rittal offers its customers solutions for the TS 8 enclosure that meet the requirements for various earthquake zones. The company also examines the earthquake protection of enclosures in test laboratories and has published a new white paper full of practical advice on the subject.

Despite all the technical equipment available to measure natural disasters, earthquakes remain incredibly hard to predict. To prevent damage in the event of an earthquake, both buildings and the electrical and technical infrastructure such as switchgear installations have to be “earthquake-resistant”. The safety of enclosures in particular is of great importance, as the stresses exerted on a switchgear system by an earthquake can cause both malfunctions and structural damage. Various standards define the requirements such enclosures have to fulfil in order to qualify as “earthquake-resistant”. Different standards apply depending on the particular application and geographical target market.

Combined with the appropriate sheet steel base/plinth, the standard version of the Rittal TS 8 enclosure meets the Telcordia GR-63-CORE requirements for earthquake zones 1, 2 and 3. The basic premise of this standard is that control and switchgear systems need to offer a high level of structural resilience to various influences such as humidity, fire, pollutants and earthquakes. The document refers to the designated zones in the United States (zones 0 to 4), where zone 0 represents a very low risk and zone 4 a high risk of earthquakes.

Upgrading with specialist accessories

For earthquake zone 4, the TS 8 can be upgraded using a Rittal earthquake kit. This additional reinforcing structure is based on the same principle as timber framing. The optional accessory stiffens the enclosure frame so that the system complies with even the strict zone 4 requirements of GR-63-CORE. It consists of bracing struts that are screw-fastened to the sides of the frame to significantly increase its rigidity. Gusset plates in the corners add extra stability. A reinforced base/plinth is also available for fastening the enclosure to the floor for earthquake protection.

Safety tests on a shaker table

To prove that enclosures can withstand the effects of shocks and vibrations, tests are conducted in specialist laboratories. A shaker table is used to simulate the effects of an earthquake – i.e. vibrations and shock stresses. The test piece must not incur any structural damage as a result. The precise test requirements vary according to the standard in question, particularly regarding the exact frequency spectrum and related accelerations.

Information and advice at a glance

Rittal provides practical advice in the new “Earthquake protection for switchgear systems” white paper. It contains everything you need to know about current standards, typical test methods and designing enclosures to withstand earthquakes. Specifically, it covers the following issues: What needs considering when con-structing electrical switchgear systems in regions that are potentially earthquake-prone? What damage can an earthquake cause to a switchgear system? And which standards apply in relation to the electrical infrastructure? It also provides information about typical test methods for examining the earthquake protection of an enclosure, such as testing earthquake safety using a shaker table.

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