Seismic Testing - Clark Testing - IEEE 693

IEEE 693: Seismic Testing for Electrical Transmission & Distribution Equipment

It is estimated that the seismic events, such as the 1989 Loma Prieta and 1994 Northridge earthquakes in California inflicted roughly $283 million worth of damages and losses on Sub-station equipment. IEEE-693 is a document that primarily directs the design and qualification of equipment installed in sub-stations and its ability to withstand a seismic event.

Substation equipment can be qualified by doing static analysis, dynamic analysis, or shake table testing depending upon the type of equipment and voltage rating. The shake table at Clark Testing is able to qualify power transmission & distribution equipment for the latest version of IEEE 693-2017. Clark Testing was one of the first labs to test to this latest revision. Qualification testing on substation equipment at Clark’s lab has typically included bushings, insulators, disconnect switches and transformers.

Seismic qualification is conducted in accordance with the three qualification levels identified in IEE 693 depending upon the location and anticipated ground acceleration. The performance levels include low (0.1 g), moderate (0.5g) & high (1.0g). IEEE-693 standard Required Response Spectra (RRS) are used for the analysis and testing of equipment. The infinite frequency or Zero Period Acceleration (ZPA) of the high and moderate RRS is .5g and .25g respectively.

The Seismic table at Clark Testing is capable of performing seismic testing on large packages up to 20,000 lbs. at 1g ZPA. The table can achieve 3g’s ZPA up to 10,000 lbs. & 5g’s for lower weight. The table has three (3) independent servo hydraulic actuators with 38,000 lbs. force +/- 5” stroke with peak acceleration of 15g – 18g. Clark testing can accommodate insulators up to heights of 35 feet tall.

In addition to the seismic shake test, Clark also provides static pull testing to determine the natural frequency, environmental testing for thermal cycling and EMC/EMI testing.

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