with a new twist

The campaign continues--with a new Twist

Dr. Hasse's personal 10/350 campaign is apparently not quite over. In 2010 he wrote Chapter 7 of a book entitled "Lightning" published by the Institute of Engineering and Technology, London, UK. In Hasse's prose the 10/350 drum beat once more: "At the boundaries of LPZ 0... SPDs must be used, which are capable of discharging considerable partial lightning currents... These SPDs are called lightning current arresters (SPDs class I) and are tested with impulse currents, waveform 10/350μs." As usual he included lots of photographs of Dehn spark gap protectors.

But this time he went one step further. He "recognized" the ability of an MOV surge protector to stand in place of a spark gap "if the specified nominal discharge current 8/20μs was at least 25 times the specified 10/350μs discharge current." For example, for an MOV SPD to pass a test specified for 25kA 10/350μs, it would have to be subjected to an impulse current of "at least" 625kA 8/20μs. Does anyone have any idea where Dr. Hasse comes up with this stuff?

The Hasse politically correct equivalency factor has now gone from 10 to 30 to zero. Then up to 25 and now to "at least 25." (see the earlier page in this series.) We suppose you could say that Dr. Hasse was in favor of an equivalency factor both before and after he was against it.... He even created a new illustrative chart for inclusion in the 2010 book. You can see it here to the right. Who knows, if somebody doesn't do something quick, it's likely that the next time you see it will be in the next re-write of the IEC 62305 Series.

The Corporate Campaign Continues

Dehn and Sohne's 30-year corporate campaign to promote the 10/350 waveform continues to this day. The following quote from the Dehn website in August 2013 rejects any idea of an equivalency factor. It says: "DEHN believes it is necessary to test with the actual 10/350 μs waveform...only testing with the 10/350 μs waveform is truly representative of performance for protection against direct lightning strikes."

Click here to see the entire page.


In case anyone is taking this "personally" please accept the fact that this website is not meant to be a rant on any particular person or company. Its entire object is to improve the state of lightning protection. And though it may take courage to stand up and speak, it takes just as much courage to sit down and listen.

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