a. Explain TWO benefits of partial discharge analysis on high voltage cables in term of manufacturers’ perspectives. Present your findings according to the actual examples in high voltage industries.

 

b. Table 2 shows the properties of insulating materials, A, B and C. According to the data, evaluate the heat profile under nominal frequency for TWO different types of materials. Clearly state your notations and the assumptions made.

c. The construction of a high voltage cables is proposed. This single-core high voltage cable has a conductor, diameter = x cm and a inter sheath has a radius of d cm. If two inter sheaths are used, determine the best positions, the maximum stress, and the voltage of the inter sheaths. Clearly state your notations and the assumptions made.

d. A few changes are made to improve the performance of cables in Q2c. In present, the distances between inter sheath are spaced equally from each other, the sheath, and the conductor. Analyze the electrical stresses in each layer and obtain the maximum stresses from your calculation. Clearly state your notations and the assumptions made.

Table 2 Characteristics Conductivity (S/m) Dielectric strength Dissipation factor AC Dielectric strength (kV/cm) DC Dielectric strength (kV/cm) A >10-15 2.3 0.0002 720-900 600 Materials B >10-16 2.35 0.0002 190-240 150 >10-16 2.3 0.0005 210-280 180