1. In a coaxial power cable the radius of the conductor is 25 mm and the thickness of insulation is 8 mm. Calculate the Schwaiger factor n in this field configuration. Comment on uniformity of electric field. 2. What will be the most economical (optimum) conductor diameter of a single core power cable to be used on 132 kV power systems? Also find the diameter over the insulation provided to the conductor if the maximum permissible stress is not to exceed 8 kV/mm. 3. Two parallel plates which are oppositely charged are placed 5 cm apart. The potential difference, in volts, between the plates is 100 kV. Find the electric field intensity between them. 4. In a 220 kV rated voltage coaxial spherical system of a GIS the radius of the inner HV electrode is 10.0 cm and the SF6 gas insula- tion thickness of 18.0 cm is provided around. Find 1. 0.868, weakly non-uniform. 2. 19.04 mm, 51.79 mm 3. 2 kV/mm 4. (a) 19.75 kV/cm, 2.52 kV/cm, 0.357 (a) The max and min electric field intensities and the Schwaiger factor in the system. (b) For the given system voltage and fixed outer radius of the coaxial system, what changes in the configuration will be needed to optimise the max field inten- sity in this system? What will be its value then? 5. If a potential of 5 kV is applied across gap distance d' of 5 cm in air between (a) the uniform, (b) weakly nonuniform and (c) extremely nonuniform field electrode systems shown in Fig. 2.1, find the maximum field intensities, Emax at the high-voltage electrode in each case? 6. In which case is the dielectric properties of air utilized least? (b) Radius of HV conductor 14 cm, 18.14 kV/cm 5. 1 kV/cm, 4 kV/cm, 100 kV/cm 6. Extremely non-uniform field Field lines Equipotential lines Field lines Equipotential lines (a) (b) Figure 2.1 ■Typical electrostatic field configurations: (a) Field between sphere or cylinder and plane; (b) field on a bundle of four conductors carrying the same potential as used in transmission lines.

2- Draw and explain the phasor diagram for two transformers in parallel.

Two 11,000/2,200-V, 1-phase transformers are connected in parallel to supply a total load of 200 at 0.8 p.f. lagging at 2,200 V. One transformer has an equivalent resistance of 0.4 ohms and equivalent reactance of 0.8 ohms referred to the low-voltage side. The other has equivalent resistance of 0.1 ohms and a reactance of 0.3 ohms. Determine the current and power supplied by each transformer.

A 10 MVA three phase load is to be served by a three phase transformer at aline voltage of 13.8 kV. The supply side voltage(line-line) is 138 kV. Varioussingle phase transformers are available in the warehouse but all havewindings with voltage ratings under 100 kV and current ratings under 250 A.Is it possible to serve the load using only three single phase transformers? Ifso, specify the three phase connections and the low and high voltage ratingsof the single phase transformers.

Define all the losses in the transformer with the diagram and then define the hysterisis loss with thw graph.

Subject - Design electrical circuits for single-phase AC networks Question - Compare the effect of varying resistance, capacitance and inductance in parallel and series AC circuits on voltage, resistance and impedance

Consider the three single-phase two-winding transformers shown in Figure. 3. The high-voltage windings are connected in Y. (a) For the low-voltage side, connect the windings in A, and label the terminals a, b, and c in accordance with the American standard. (b) Relabel the terminals a', b', and c' such that VAN is 90° out of phase with V₂'b' for positive sequence. DI H₂ Figure. 3: Three-Winding Transformer

Three single-phase transformers, each rated 10 MVA , 66.4/12.5 kV, 60 Hz , with an equivalent series reactance of 0.1 per unit divided equally between primary and secondary, are connected in a three-phase bank. The high-voltage windings are Y-connected and their terminals are directly connected to a 115-kV three-phase bus. The secondary terminals are all shorted together. Find the currents entering the high-voltage terminals and leaving the low-voltage terminals if the low-voltage windings are (a) Y-connected and (b) Δ- connected.

Three single-phase two-winding transformers, each rated 3kVA,220/110volts,60Hz, with a 0.10 per-unit leakage reactance, are connected as a three-phase extended autotransformer bank, as shown in Figure 3.36(c). The low-voltage winding has a 110 volt rating. (a) Draw the positive-sequence phasor diagram and show that the high-voltage winding has a 479.5 volt rating. (b) A three-phase load connected to the low-voltage terminals absorbs 6 kW at 110 volts and at 0.8 power factor lagging. Draw the per-unit impedance diagram and calculate the voltage and current at the high-voltage terminals. Assume positive-sequence operation.

A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a balanced load of three 1, Y-connected resistors. Choosing a base of 90MVA,66kV for the high-voltage side of the three-phase transformer. spify the base for the low-voltage side. Compute the per-unit resistance of the load on the base for the low-voltage side. Also, determine the load resistance in ohms referred to the high-voltage side and the per-unit value on the chosen base.