With bundled conductors

Question

Examoogle · Accepted Answer

Option A: Corona inception voltage increases

Explanation & Concepts:
Bundled conductors increase the effective radius of the transmission line, which significantly reduces the surface voltage gradient. Since the corona inception voltage is directly proportional to the effective radius of the conductor, bundling leads to an increase in the corona inception voltage.

Working Principle: Corona inception depends on the electric field intensity at the conductor surface, given by $E = \frac{V}{r \ln(D/r)}$. By using bundled conductors, the geometric mean radius (GMR) increases. This increase in effective radius ($r_{eff}$) reduces the surface stress for a given applied voltage, delaying the air ionization process and thereby increasing the inception voltage.

Key Formulas: $V_c = g_0 \cdot \delta \cdot m \cdot r \cdot \ln(\frac{D}{r})$ — Corona inception voltage formula; $E = \frac{V}{r \ln(\frac{D}{r})}$ — Electric field intensity at conductor surface

Key Points: Bundling increases the Geometric Mean Radius (GMR) of the conductor arrangement.; Higher effective radius reduces the maximum electric field stress on the surface.; Corona loss is inversely proportional to the square of the inception voltage.; Bundled conductors improve transmission efficiency by reducing corona loss and radio interference.

Advantages: Reduced corona loss; Lower line reactance (reduced inductance); Higher surge impedance loading (SIL); Reduced radio and television interference

Disadvantages: Increased wind load on towers; Complex hardware requirements (spacers); Increased cost of installation

Applications: Extra High Voltage (EHV) lines (400 kV and above); Ultra High Voltage (UHV) transmission lines

Additional Info: The corona inception voltage ($V_c$) is the critical voltage at which the dielectric strength of air breaks down.. Option B is incorrect because bundling reduces surface stress, which pushes the threshold for ionization to a higher voltage level.

Answer: A is correct — Bundled conductors increase the effective radius of the line, which decreases the surface voltage gradient and consequently increases the corona inception voltage.

Exam Tip: Always remember that any design change increasing the effective surface area of a conductor (like bundling or increasing radius) helps in mitigating corona effects by lowering surface potential gradient.

Examoogle · Answer

Option B: Corona inception voltage decreases

Examoogle · Answer

Option C: Corona inception voltage remains unaffected

Examoogle · Answer

Option D: None of above

Correct Answer

Discussion (0)

Correct Answer

Related Questions

Discussion (0)