Q1. Explain suspended particle theo

Q1. Explain suspended particle theory and cavitation & bubble theory in commercial liquid dielectrics.
Q2. Explain electronic breakdown and electro-convection breakdown in commercial liquid dielectrics.
Q3. In an experiment with certain gas, it was found that the steady state current is 5.5 X 10-8 A at 8KV at a
distance of 0.4cm between the electrode plates. Keeping the field constant and reducing the distance to
0.01cm results in a current of 5.5 X 10-9A. Calculate Townsend’s primary ionization co-efficient.
Q4. In an experiment with certain gas, it was found that the steady state current is 6 X 10-8 A at 10KV at a
distance of 0.4cm between the electrode plates. Keeping the field constant and reducing the distance to 0.2cm
results in a current of 10 X 10-9A. Calculate Townsend’s primary ionization co-efficient.
Q5. A steady current of 600 μA flows through the plane electrode separated by a distance of 0.5 cm when a
voltage of 10 kV is applied. Determine the Townsend’s first ionization coefficient if a current of 60 μA flows
when the distance of separation is reduced to 0.1 cm and the field is kept constant at the previous value.
Q6. A solid dielectric specimen has a dielectric constant of 4.2, ad tanδ = 0.001 at a frequency of 50 Hz. If it
is subjected to an alternating field of 50 kV/cm, calculate the heat generated in the specimen due to the
dielectric loss.
Q7. A solid dielectric specimen with a dielectric constant of 4.0 shown in Fig. 7 has an internal void of
thickness 1 mm. The specimen is 1 cm thick and is subjected to a voltage of 80 kV (rms). If the void is filled
with air and if the breakdown strength of air can be taken as 30 kV (peak)/cm, find the voltage at which an
internal discharge can occur.
Fig. 7
Q8. The following observations were made in an experiment for determination of dielectric strength of
transformer oil. Determine the power law equation.
Gap Spacing: 4 6 8 10
Vb (kV): 88 135 165 212
Q9. The following observations were made in an experiment for determination of dielectric strength of
transformer oil. Determine the power law equation.
Gap Spacing: 4 6 10 12
Vb (kV): 90 140 210 255
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