Nonstandard Lightning Protection System
ESE/ CSE/DAS lightning protection in India
A rod capturing a lightning and passing the lightning current to the soil without damaging anywhere through a 70 SQMM copper flexible cable is called as advanced / modern lightning protection in India. As per the claims of the manufacturers, such rod attracts lightning from a distance of up to 110 meters, thereby protects an area of up to 200 meters (dia). They are also called early streamer emission (ESE), or controlled streamer emission (CSE) lightning protection systems.
As such the illusory idea of one rod protecting 200 meters (dia) looks impressive, added with names such as advanced, modern and active lightning rods, with a test certificate from CPRI strengthening this belief. In India, nearly 70% of industrial and commercial LPS installations use ESE type LPS. Almost 100% Solar PV installations follow ESE devices.
Unfortunately the actual scientific facts are not very favourable to these types of systems.
The concept of ESE rod in India
The available literatures and documents claim that these rods “attract lightning” and protect structures within a radius of up to 110 meters. Due to the apparently fascinating story, the system seekers believe that this “active” method is “modern and advanced” in comparison to the “passive” “conventional” franklin rod which is 250 years old. Electrical managers are attracted towards this illusion and raise only one question “how many meters will it protect??”. There are claims that even these rods protect an entire village or a town !!!
In most of the cases of ESE systems used in India, the single down conductor that runs from the lower end of the air-termination to the ground level is insulated by a material cover which is claimed to be a high voltage insulation. Thus, it is separated from the rest of the structure. There are cases where the length of the down conductors is more than 100 meters.
The down conduct is then connected to a chemical earth pit which is claimed to dissipate the lightning current easily into the earth due to some “advanced chemical content”.
The claim (protects 100’s of meters)
The difference in the time of initiation of the upward streamer by a conventional rod and an ESE rod is the “time advancement” of an ESE air termination (∆t). Then considering a streamer speed of 106 m/s, the ESE manufacturers claim that their rods have a height advancement of ∆t × 106 m over the conventional rod. The value of ∆t is computed by observations of 2 m long rod – rod gap applied with laboratory sparks as per the NFC 17-102 and then extrapolating the results to many tens of meter long upward leader.
Scientific communities, including the leading Standard committees in the world, strongly reject these claims, as the available experimental and theoretical knowledge falsify the computation method of ∆t. Even the speed of the answering leader is measured to be 104 - 105 m/s, as per the latest fast video techniques available at present. This results in 10 -100 times decrease in the efficiency (height advancement) of these rods. The working principle of these rods are included either in IS standards or in IEC and most other international/national standards.
Explanations from the standard NFC17-102
Even if we consider the NFC17-102 is acceptable, the methods practised in India becomes highly questionable. The system as per the standard is shown in figure B4 consisting of
1. ESE air terminal;
2. Down conductors (several down conductors are necessary);
3. One specific earth electrode for each down conductor and a foundation earthing system;
4. Several equipotential bonding between the building metal parts and LPS.
As such, the standard explains about a proper equipotential bonding system and a LPS, rather than isolating the down conductor which may cause dangerous potential differences between the down conductor and the nearby metallic parts of the structure.
The standard also explains about the conditions of multiple down conductors, methods of calculating separation distance, methods of equipotentialisation, conditions with which efficiency (radius of protected area) is reduced etc.
In contrast, the installations in India follow a deceptive concept and claim that are conforming to NFC17-102 standard. Other than the air terminal, one down conductor and an earth pit - balance safety measures recommended in the standard are missing in India, making the installation highly vulnerable to lightning strike.
CPRI test
NFC17-102 recommend the ESE rod to be tested to prove its ∆t, as this is the most important parameter deciding the controversial protection radius. However the rods sold in India are tested with a totally different concept.
ESE rods sold in India are tested at CPRI for a short time current flow of few kA’s. This test at CPRI have no relation to the ESE concept. However users accept this test report as a proof of the efficiency of ESE rods.
Tenders and purchase notices published in media show that ESE rods with CPRI test report have become a normal practice in various government agencies. This nonstandard method is also accepted by safety agencies such as the electrical inspectorates in few states.
Dangers of advanced/modern LPS installation, recommendation not to use by NBC-2016
ESE systems installed in Industrial, Commercial, High-rise, Explosive areas (oil and gas industry), Power generating stations, Telecom SOLARPV, .... .... pose a serious threat to the building and its contents. National Building Code of India (NBC-2016) in clause 11.5.1 (air-termination) (volume-2, part-8 building services, section-2 electrical and allied installation) mentions.
“Radioactive air terminals shall not be allowed. Any other kind of air-terminal like dissipation system / ESE air-terminal / CSE air-terminal shall not be acceptable”
Recommendation: Electrical safety engineers and safety auditors are requested to ensure that nonstandard practices are not followed.
Note for insurance companies - Installation which are not fulfilling the basic minimum safety requirements as per the IS/IEC standards are technically unfit for compensation in case of an accident. |
Note:
“International Standards” in the World Trade Organization (WTO) treaty on Technical Barriers to Trade (TBT), applies only to IEC, ISO and ITU standards.
Statement such as “electrical system running for decades without accident”, is mere luck and will not guarantee an accident free environment in future.
Video of the webinar the facts and truth of Lightning protection