Lightning and Surges, Myths and Facts
Air Terminal in an external lightning protection systems can be divided into two categories, namely, conventional and non- conventional. The conventional systems use Franklin rods or mesh. Early Streamer Emission (ESE) and Dissipation Arrays (sometimes called Charge Transfer Systems – DAS / CTS ) are the
non conventional air terminals.
Many decades of experience shows that Franklin rods or mesh located at critical points on a structure with a proper down conductor and earthing system, the damage due to lightning on the structure could be UHGXFHG VLJQLÀFDQWO\. 7R SURWHFW HOHFWULFDO DQG HOHFWURQLF
systems with in the structure SPD’s are necessary. The
system is accepted and appreciated by all national / international standards.
Early Streamer Emission
ESE manufacturers claim that ESE terminals are equipped with discharge triggering device to initiate streamers and increase the probability of connecting to a downward leader. The time advantage realized by the early inception of the connecting leader from an ESE terminal in comparison to a normal Franklin rod would provide a possibility interception at a longer distance in comparison to that from a Franklin rod. Consequently, it is claimed that under similar circumstances an ESE terminal will have a larger protection area than a Franklin rod of similar dimensions.
([SHULPHQWV DQG LQYHVWLJDWLRQV ÀQG WKDW WKHVH FODLPV
are baseless. How ever these rods are accepted in the French standard as an additional standard (in addition to EN 62305)
Practical Issues in India
ESE rods are installed in almost every building in India. Some are made in Europe/China and balance in India. As a proof of reliability ESE manufacturers claim test reports from CPRI. Mistakes done in India are
- ESE rods are tested with a short current pass of few KA (an iron rod also pass this test). This test report have nothing to do with the principle of ESE
- ESE rods with one insulated down conductor is used. Even insulated cable through the steel sheet of a PEB building. This is against the French Standard itself
- Down conductors are installed with number of bends and often through electrical This create serious threat to electronic installation in the building
NF C 17-102: 2011 (French standard on ESE rods) explain as below
Level of protection I +: The ESE system at level of protection 1 is additionally connected to the metal structure or reinforced bars of the building in addition to the dedicated down conductors included in the ESE system at roof level and ground level. When down conductors are not interconnected at roof level, a ring conductor located above the roof can be used to achieve this requirement….. If there is no natural down conductors or if the above requirement can not be IXOÀOOHG, OHYHO 1+ FDQQRW EH DFKLHYHG.
Level of protection I++ : WKH URRI LV SURWHFWHG DW ,+ ZLWK an ESE terminal having radius of protection reduced by 40 %.
The above clause from French standard shows ESE protections is just like doing a conventional Lightning Protection system with an extra ESE rod and down conductor. Even ESE suppliers don’t know such points from the ESE standard
(6( DLU WHUPLQDWLRQ SULQFLSOH GR QRW FRQÀUP WR ,6
standards, National electric code, National Building Code as well as CEA safety regulations. As per CEA regulation every building with more than 15 meter height shall be protected as per IS/IEC 62305. In spite of this, large number of industries and commercial buildings use ESE rods (always with one down conductor). Users consider ESE rods as they believe it is the easiest way of doing lightning protection, but are never aware of the dangers behind it. Such installation create serious threat to the structure as well as its contents.
Critical telecom installations in India were using ESE
URGV D GHFDGH EDFN, ÀQGLQJ LWV LQHIÀFLHQF\ LQ SURWHFWLRQ
ESE rods were replaced with DAS.
Dissipation Array System or (Charge Transfer System)
The original idea of lightning eliminators or dissipation arrays is to utilize the space charge generated by one or several grounded sharp points to “dissipate” (i.e. neutralize) the charge in thunderclouds and thus prevent lightning strikes to a structure to be protected. The manufacturers of this system claim that the space charge generated by the array will silently discharge the thundercloud.
The idea of DAS means an area with number of DAS systems will never experience a lightning hit. The idea seems to be attractive, but it is the peak of exploitation. Engineering community never accepted DAS.
DAS in a telecom tower
DAS has been installed widely in India especially for critical telecommunication application. After every failure, DAS supplier reply to users that the lightning which created failure is higher than the capacity of that particular model of DAS. Manufacturer recommend to replace the existing DAS with a bigger one at extra cost after every failure.
Both ESE and DAS installations in India do not provide any protection to structure, Electronics and
+XPDQ EHLQJV, LW DOVR LQFUHDVHV WKH FKDQFH RI ÀUH LQVLGH
the building. These devices are widely used due to the attractive features explained in the catalogue.
Insurance companies deny ESE as a protection device and ask users to replace it with conventional system FRQÀUPLQJ WR ,6/,(& 62305.
An installation properly designed and installed satisfying Indian standards IS/IEC 62305, IS 3043, IS 732 will protect the installation for years with out maintenance.
National Building code (2015-draft) recommends not to use these non conventional system. Lightning protection as per IS/IEC 62305 is mandatory for buildings more than 15 meter height as per CEA safety regulations (2016-amendment draft). With these code & regulations in place it becomes a legal requirement now to use conventional system and not ESE and DAS.
Courtesy: published research papers of Mr. M.A. Uman and Mr. V. A Rakov & Mr. HARTONO Zainal Abidin.
Lightning Protection System
&RPSDULVRQ FRQÀUPLQJ WR ,6/,(& 62305 VWDQGDUGV DQG (6( URGV
This comparison is made based on the installation practices prevailing in India. NFC 17-102 ESE standard require down conductors and earthing as per IEC 62305 which is not followed in India. (refer French standard NFC17-102:2011 on ESE rods)
|Design Standard||,6/,(& 62305||NFC 17-102:
|1||Name usually used||Conventional Lightning Protection||Advanced Lightning protection|
|2||Protection||ELPS for structure||Focused only|
|required||and SPM for||on ESE rod.|
|against||contents. All||No protection|
|Lightning||requirements cRQÀUmed||provided against
|potential & EMC|
|Yes. Accepted world wide (including france and spain as||NO (except french and spain as an additional|
|main standard)||standard – due|
|to local business|
|4||Theory Behind||Faraday Cage||only highlighting the rod|
to IS standard
|6||Testing||IEC 62561 – 1 to 7||Short circuit & surge current from CPRI. Both tests are not related to ESE theory|
and CEA regulation
|NBC of India – 2016 banned use of ESE|
|8||Level of protection||Class 1 to 4||Class I and I|
|Air Termination and Down conductor recommendations
|For both classes structural steel as down conductor is mandatory.
Additional exposed down conductors
in multiple locations are also required (ref
220.127.116.11 of NFC 17-102:
|2011). But in India one or two exposed down conductors alone are used|
|Expected problems of ESE rods|
to French standards – ESE standard recommend to reduce the coverage radius
buildings, which is not done India
electronics failure, step potential, touch potential, EMC. Focused only on ESE air terminal rod
|3||Fire and Flash over due to 1 or 2 down conductors. Recommendations as per ESE standards are not followed especially usage of natural down conductors|
|4||Insurance companies also reject ESE rods as a result number of industries installed conventional LPS at extra cost|
|5||One world famous ESE manufacturer claims ESE rods as per NF-C standards will not work !!!!!!!!!!!!!.|