Breakdown in Pure and Commercial Liquids

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Breakdown in Pure and Commercial Liquids

Q. Explain the phenomenon of ‘ tracking in solid insulating materials under electrical stress. How it can be minimized.

  • Pure Liquids Liquids which are chemically pure, structurally simple and do not contain any impurity even in traces of 1 in 109, are known as pure liquids. E.g. n-hexane (C4H14).
  • In contrast, commercial liquids used as insulating liquids are chemically impure and contain mixtures of complex organic molecules.
  • In fact their behaviour is quite erratic.
  • No two samples of oil taken out from the same container will behave identically.

e.g. transformer oil

Breakdown in Pure and Commercial Liquids

Pure

Commercial

Pure liquids are those which are chemically pure and don’t contain
any other impurity even in the trace of 1 in 109, and are structurally
simple.

Commercial insulating liquids are not chemically pure and have
impurities like gas bubbles, suspended particles etc. These impurities reduce
the breakdown strength.

The breakdown voltage depends on,

1. The applied field

2. Gap separation

3. Cathode Work Function

4. Liquid viscosity

5. Liquid Temperature

6. Density and molecular structure of liquid

The breakdown mechanism depends on,

1. Nature and condition of the electrodes

2. Physical properties of the liquid and

3. Impurities and gases present in the liquid

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