Surge Suppressors energy Level Calculation Sheet

Maybe this can help?

https://docs.google.com/viewer?a=v&q=cache:Gej_2tHu1r8J:www.eaton.com/ecm/idcplg?IdcService%3DGET_FILE%26allowInterrupt%3D1%26RevisionSelectionMethod%3DLatestReleased%26Rendition%3DPrimary%26%26dDocName%3DSA01005003E+surge+suppressor+calculation&hl=en&gl=jp&pid=bl&srcid=ADGEEShXNI-Q4J0EUmQPTji_D4hdAx834vxQ2QaWYuTxh1Elij9DaB5FwyuCafLrPZ55Py7HyGqmFvuNLVuY4zXPJD2TD7k1K1AtPFuIHWukkhDW4IYYDJ9B8QU5oCUhQ_lg5QXSKLPC&sig=AHIEtbQWQXgm-i3MUs8X0w23Rw_NbA_QuQ

Or this doc

http://www2.schneider-electric.com/documents/technical-publications/en/shared/electrical-engineering/electrical-environmental-constraints/low-voltage-minus-1kv/ect179.pdf

thks for yr feedback

For the sake of this discussion, I just wanted to help make a thing or two clear. There are two basic kinds of devices available.

The kind of device that is in series with your load is generally a limiting device that is mostly inductive. By that, I am including the filtering type of circuits that may also have some bypass (to ground) capability. They are generally good for "dirty power" issues.

The kind of device that is in parallel with your load is generally a shunting device that remains off until the peak arrives. Then it turns on and provides a low impedance path to ground. As soon as the peak is gone, it turns off. But the problem is that if it is destroyed, how would you know? For a data centre, it may be necessary to have both.

Incidentally, the parallel type generally uses MOV's (metal oxide varistors) and it is important that they are located very close to the electrical power connection. If you put a MOV type of suppression on an extension cord as an "afterthought" then it might as well not be there.

I just want to provide additional information about the second type of device: the Surge Protection Device (SPD)must be designed in accordance to IEC 61643-11/2011 or UL1449 3rd Ed . In both cases, the standard requires a LED or mechanical flag on front face of the SPD when the MOV is in the way of a short circuit .In most cases, there is also a remote transfer of this information

On the other hand, if your facility has a high lightning risk, then the installation standard IEC 60364-4-443 recommends the installation of a SPD in the incoming mainboard to divert the lightning current to the earth and to avoid that it spreads throughout the electrical installation

For more information I suggest you refer to the following website: http://www.electrical-installation.org/enwiki/Protection_against_voltage_surges_in_LV

DM