Seismic Rating of Electrical Equipment
Seismic Rating of Electrical Equipment
(OP)
I'm curious about how others working in high seismic risk areas are specifying electrical equipment for typical utility or industrial use.
Do you require equipment to merely survive the seismic forces or to actually stay in service?
What type of response do you get from equipment suppliers?
Thanks,
dpc
Do you require equipment to merely survive the seismic forces or to actually stay in service?
What type of response do you get from equipment suppliers?
Thanks,
dpc






RE: Seismic Rating of Electrical Equipment
RE: Seismic Rating of Electrical Equipment
I know that Cutler-Hammer has done quite a bit of testing on a shaker table for a lot of their equipment. But for many types of high voltage substation equipment, we find that no manufacturer (in U.S.) has done any actual testing, probably due to the cost. They routinely take exception to any seismic requirements.
dpc
RE: Seismic Rating of Electrical Equipment
RE: Seismic Rating of Electrical Equipment
A rating of 0.4 G's is not much. Is this a sustained force over some period of time or is it a short duration?
RE: Seismic Rating of Electrical Equipment
RE: Seismic Rating of Electrical Equipment
I have had more trouble with conduit and tray installation than with equipment. Conduit and tray are typically installed without design drawings and it is harder to certify the installation will meet the seismic installation criteria. Be
B-Line, Unistrut and other strut manufactures have installation details that cover many situations. Some of the more complex installations ( like a rack of 10 plus conduits or two or three cable trays ) are not covered in the "cookbook" details. In some cases we have used a structural engineer to design or review design of "as built" hangers.
You may have to go into more detail for the installation of hangers such as numbering them and making detailed drawings of them( so you can document design and installation). Building codes require that some fasteners require witnessing to assure that they were torqued correctly. In short it may require you do business in ways you havn't done before.
If your in a seimic zone that requires an installation to meet a prescribed criteria it's better, cheaper and faster to plan on it from the start rather that later. I've seen it done both ways.
RE: Seismic Rating of Electrical Equipment
ANSI C37.81 was developed for nuclear applications and is quite severe.
The UBC requirements were intended to be applied to structures and not equipment, so there are sometimes conflicts.
My understanding is that UBC Zone 4 specifies an acceleration of 0.75g. The California BC Zone 4 requirement is 1.75g. Cutler-Hammer claims to have tested their gear to 2.0g. I believe ANSI C37.81 is higher than this.
As far as I know, not many manufacturers are doing any testing. It would be difficult for a large device such as a substation transformer. But switches and regulators could be tested if there was sufficient demand.
RE: Seismic Rating of Electrical Equipment
There is practical limitation on the shake-table size, weight, displacement, velocity and acceleration of the to test large and heavy power equipment such as power transformers, reactors, capacitor banks, complex structures, etc. In those cases, combination of static, dynamic and time history shake-table test could be acceptable to seismic qualify power equipment in accordance with IEEE Std 693-1997.
Equipment mounted in high structure could experience heavier vibration than those tested at ground elevation. Anchoring method, foundation, soil type, equipment mounting, structure type, cable, loading combination, should be considered to qualify the seismic performance of the assembly.
Caution is advice went compare foreign equipment tested based only in the acceleration parameter such as 0.5g. There are in the US qualification and performance levels (high, moderate and low) base on vibration spectrum consideration that should be taken in account to be in compliance with the latest seismic requirement of IEEE and supplementary building codes.
RE: Seismic Rating of Electrical Equipment