# Technical Interview: Electrical and Electronics Engineering: Questions

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## Electrical and Electronics Engineering

221) Differentiate between mho relay and offset mho relay characteristics.

222) Explain the working principle of differential protection. Explain the difficulties to implement.

223) Explain how % basic setting and % pickup value is set for differential relays.

224) What do you understand about % age of winding protected and % age of winding is unprotected.

225) Explain the working principle of transverse percentage differential protection for multi-winding generators.

226) State the factors governing the selection of a pilot protection scheme. Explain the working principle of carrier pilot protection scheme.

227) Define sub-transient and steady state reactance՚s of an alternator.

228) Draw zero sequence networks of loads connections for star underground neutral, star grounded neutral, star grounded neutral with an impedance and delta connected loads.

229) Explain formulation of using nodal method and singular transformation method.

230) Define sparsity. What is the value of sparsity of Ybus for a practical power system?

231) What are the assumptions made to develop relation between bus voltages and bus currents in load flow studies?

232) Define voltage regulation and efficiency of a transmission line. Explain the effects of load power factor on regulation and efficiency.

233) Draw phasor diagrams and write A, B, C and D parameters for nominal T and circuit of transmission line.

234) Derive A, B, C and D parameters for nominal T and methods.

235) Explain how to determine A, B, C and D parameters of a transmission lines.

236) Explain how to determine ve, ve and zero sequence impedances of transmission.

237) Explain how to determine ve, ve and zero sequence impedances of alternators.

238) Explain phenomenon of current chopping in vacuum circuit breakers. State the properties of contact materials used for vacuum interrupters.

239) Define switchgear and differentiate between low voltage switchgear and high voltage switchgear.

240) Define coefficient of earthing and state the significance of it in selection of voltage rating of surge arrester.

241) Explain about single frequency transient and double frequency transients.

242) Explain the working principle of current limiting reactors and explain why we need these reactors in power systems.

243) Explain the principle of directional element. Draw and explain impedance relay characteristics with directional element.

244) What do you understand about power swings and explain its effects on distance relays.

245) Define reach and under-reach of distance relay. Explain the effect of arc resistance in distance relays.

246) Draw voltage characteristics of surge arrester and define residual voltage, impulse spark over voltage and power frequency voltage of a surge arrester.

247) Draw the phasor diagrams of synchronous generator feeding constant active power into infinite bus bars as excitation is varied.

248) What do you understand about insulation coordination, protection margins and protective ratio?

249) Explain the N-R method of load flow studies. Explain the reasons for the order of Jacobian in N-R method using polar coordinates is smaller than in N-R method using rectangular coordinates.

250) What is travelling wave? Explain the concept of standing wave and voltage standing wave ratio.

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