What is Townsend theory?

The Townsend discharge or Townsend avalanche is a gas ionisation process where free electrons are accelerated by an electric field, collide with gas molecules, and consequently free additional electrons. The result is an avalanche multiplication that permits electrical conduction through the gas.

What is streamer theory?

In 1940, Rather, Meek and Loeb proposed the Streamer theory. The streamer mechanism breakdown mainly arises due to the added effect of the space-charge field of an avalanche and pho-electric ionization in the gas volume. Streamer theory predicts the development of a spark discharge directly from a single avalanche.

What is streamer in high voltage engineering?

A streamer discharge, also known as filamentary discharge, is a type of transient electrical discharge which forms at the surface of a conductive electrode carrying a high voltage in an insulating medium such as air.

What is streamer theory of breakdown?

The streamer breakdown mechanism describes the development of spark breakdown directly from a single avalanche. The space charge developed by the avalanche itself due to rapid growth of charge carriers, transforms it into a conducting channel.

What are the limitations of Townsend theory?

Townsend’s mechanism failed to explain the following: According to the Townsend theory, current growth occurs as a result of ionization processes only. But in practice, breakdown voltages were found to depend on the gas pressure and the geometry of the gap.

What is a positive streamer?

A positive streamer is a potential ionizing wave,opagates against the direction of electron drift. In ap filled with gas at near-atmospheric pressure peamers are visible as a bright filaments propawards the cathode [7].

Whats the meaning of streamer?

1a : a flag that streams in the wind especially : pennant. b : any long narrow wavy strip resembling or suggesting a banner floating in the wind.

What is current growth equation?

Townsend’s Current Growth Equation (Considering Primary and Secondary Ionization Both) Let n0 be the number of electrons released from cathode due to UV radiations. γ = Townsends secondary ionization coefficient i.e. number of electrons released from cathode per incident positive ion, photon or metastable.

What is time lag for break down?

Actually, there is a time difference between the application of a voltage sufficient to cause breakdown and the occurrence of breakdown itself. This time difference is called the time lag.

What is Paschen’s Law in High voltage studies?

Paschen’s law is an equation that gives the breakdown voltage, that is, the voltage necessary to start a discharge or electric arc, between two electrodes in a gas as a function of pressure and gap length. It is named after Friedrich Paschen who discovered it empirically in 1889.

Which of the following is the slowest Polarisation method?

Which of the following is the slowest polarisation method? Explanation: Space charge polarisation is very slow because in this case, the ions have to diffuse over several interatomic distances. Also, this process occurs at a very low frequency. 9.

What’s the difference between streamer and Townsend mechanisms?

Explain the differences between the Townsend and streamer theories of breakdown mechanisms of gap in a uniform electric field (7mks) Townsend mechanismalso called electron avalanche mechanism, is based on the generation of successive secondary avalanches to produce breakdown.

What is the Townsend and streamer theory of gaseous insulations?

Townsend and Streamer Theory of gaseous insulations -… This preview shows page 1 – 2 out of 2 pages.

How long does the streamer theory of breakdown take?

Streamer theory of breakdown • In uniform fields under very low pressures the discharge takes place based on to series of avalanches due to Townsend’s mechanism. • Hence, the time taken for ultimate breakdown is more than 10-8 sec.

What is the Townsend theory of current growth?

Below discuss about the Townsend theory: a) According to the Townsend theory, current growth occurs as a result of ionization process only. But in practice, breakdown voltages were found to depend on the gas pressure and the geometry of the gap.