Research is a fundamental part of the world of lightning protection. Since lightning phenomenon is very hard to model, analysis must also be based on extensive test campaign.

Three types of test allow Early Streamer Emission Air Terminals to be characterized:

  • Laboratory tests
  • In-situ tests – Triggered strikes
  • In-situ tests – Natural strikes


Laboratory tests

Laboratory tests are performed using a generator to produce a standardized voltage wave. This wave reproduces the conditions required to initiate an upstream leader from an Air Terminal when a negative downstream leader approaches. This enables rising tracers generated by the Early Streamer Emission Air Terminal to be characterized and early streamer emission lightning conductors to be compared with standard Simple Rod Air Terminals.

Laboratory tests

Sufficient space is needed to suspend a plate that is used to simulate the electric field generated by a cloud positioned above the Early Streamer Emission Air Terminal and the field generated by a falling tracer as it approaches the ground. A complex high voltage (dc level with superimposed impulse) is applied between the ground and the plate in order to create a discharge allowing lightning current to pass in the air between the point and the plate.

There are very few laboratories in the world able to perform this type of test. The photo on the left shows the IREQ laboratory in Canada.

The initiation time is measured either by recording the current passing through the Early Streamer Emission Air Terminal, or by recording the current of a photomultiplier (light emitted at the point).

The operation is carried out first using a Simple Rod Air Terminal, and then with an Early Streamer Emission Air Terminal. The time difference between the two measurements is called the Early Streamer Emission Air Terminal efficiency (ΔT). It indicates the effectiveness of an early streamer emission system.

A large number of measurements are used to create a graph. This shows the typically large difference between the values recorded during the two types of tests.


It can be clearly seen that not only does the early streamer emission device provide early streamer emission air terminal efficiency, but its operation is also much more regular than a simple rod.

A test protocol in compliance with NF C 17 102 Annexe C (ESEAT testing procedures and requirements) must be defined in order to obtain reliable and reproducible results in the laboratory.

The diagram on the right shows a comparison of the upstream leader currents emitted by a simple rod air terminal (SRAT) and an early streamer emission lightning rod (ESE) placed in the same electrical and geometrical conditions.

It can be seen that the SRAT current is pulsed, unlike that of the ESE. Furthermore, the ESE current is higher than that of the PTS at the instant the upstream leader is propagated.

Current in Amps


Requirements of the NFC 17-102 standard

The test requirements of the NFC 17-102 standard have been significantly strengthened in the last edition (2011).

The Early Streamer Emission Air-Terminal have now to pass a series of more stringent tests. These tests allows ESE Air Terminal to be assigned to the whole lightning factor they can face in natural conditions.

Indeed, the ESEAT have to pass the whole requirements below:

  • the marking test
  • the dimensions test
  • Environmental conditioning
  • Withstand test current (100 kA in 10/350µs waveform)
  • Effectiveness or advance time test

The last testing requirements are clearly tougher than those ib the previous edition.

It is important to note that the ESEAT are the only air-terminals with such tough requirements

Those requirements enables to show their reliability.

In-situ tests – triggered strikes

Rockets launched

Triggered strike tests are performed outside using a specially designed platform. Test campaigns are generally performed in areas that are particularly prone to lightning strikes, and are carried out at the most favourable time of year.

Rockets are launched from a launch pad; trailing a wire connected to the ground. The wire triggers a lightning discharge.
This method has the advantage to provide numerous measurements per campaign.

In-situ tests – natural strikes

Natural tests

Natural tests simply consist in placing a measuring device at a place where there is a high probability of lightning strikes.

The results obtained are indisputably the most realistic, but are also the most difficult to obtain.

There are bound to be fewer measurements obtained in these conditions. Several years are needed to collect a significant number of measurements.

Comparison of results obtained by the different systems


The above graphs compare the Upstream Leader currents emitted by a simple rod air terminal (SRAT) on three different experimental scales.

  • In a high voltage laboratory, as part of testing to NF C 17-102 (carried out by G. Berger - CNRS)
  • In a natural environment, without being triggered artificially (carried out by J.R. GUMLEY, 1992, Experiments at Kennedy Space Center, 21st ICLP, Berlin)
  • In a natural environment, artificially triggered by rocket (carried out by A. BONAMY, A. BONDIOU-CLERGERIE, P. LALANDE, P. LAROCHE, I. GALLIMBERTI, 1997, The stabilization field: a physical concept for the description of the lightning connection on grounded structures, Lightning and Mountain, Chamonix, paper B.1.2.)

Taking into account the time and current scales, it can be seen that the measured currents are very similar in the first 200 microseconds.

The validity of laboratory experiments is clear with respect to the formation phase and the start of propagation of the natural Upstream Leader.

Several in situ sites are now operational. Mention may be made for example: