Introduction:
In the ESE system, the internal design arrangement senses lightning down streamers and triggers upward leaders prior to other passive objects in the structure. Since the upward streamer is triggered in advance when compared to other conventional air terminals, the area protected by the ESE terminal will be larger than that of conventional terminals.
NFC 17-102/2011 has given the testing sequence of ESE lightning arresters.
1) Mechanical Dimension Test
2) Environmental Test
3) Electrical Test
4) Early Streamer Emission Test
Mechanical Dimension Test:
During testing, all the dimensions of the air terminals will be physically measured and the actual values will be verified with the dimensions given by the manufacturers.
Environmental Test:
NFC 17/102 explains about two different types of tests to be performed on the ESE air terminal sample to ensure its operation on adverse environmental conditions. The tests are as follows
- Salt mist treatment test
- Humid sulphurous atmosphere treatment test
Salt Mist treatment:
Salt mist treatment has to be done as per NF EN 60068 -52 standard with level 2 severity. The sample should be subjected to salt & fog (sodium chloride solution) atmosphere for 3 cycie -72 hours
Humid Sulphurous Atmosphere Treatment:
The sample should be tested in a humid sulphurous atmosphere with seven cycles and a sulphur dioxide concentration of 667 ppm (in volume).
Each cycle should be carried for 24 hours. There are two periods
- Heating Period
- Standing Period
Heating Period:
The sample should be tested at a temperature of 40°C 3°C for 8 hours.
Standing period:
The sample should be tested for 16-hour standing period.
The ESE is subjected to the following tests without cleaning after done salt & Sulphur mist test.
Electrical Test:
The ESE air terminal should be tested with a minimum of 100kA lightning impulse current at 10/350 us waveform.
Early Streamer Emission Test:
ESE should be tested for the triggering time given by the manufacturers. The difference between reference wave & measuring wave is the triggering time 'Δt'.
As per NFC 17-102/2011, the value of 'Δt' should be between 10us and 60us. An air terminal is considered as ESEAT only if the triggering advance time is greater than 10us, also the value of 'Δt' being greater than 6Ous, it is to be still considered as maximum 60us for all design calculations.
Why do the sequences need to be followed?
The sequence of testing is kept in such a manner to inspect and confirm that the ESE sample after going through the rigorous environmental tests and current carrying tests, the sample is still be able to sense downward leaders and trigger upward leaders at an advanced time than the conventional lightning air terminals. The testing sequence provided by NFC17-102 is as follows.
That's exactly why the standard says that these tests are to be carried out in the same sequence with the same sample as mentioned in their requirements to qualify the sample as an ESE type Air Terminal.
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