BEE Power Systems and Machines 5

Question 1

In a power system, the 'swing equation' describes:

Accepted Answer

The relationship between rotor acceleration, mechanical power input, and electrical power output

Answer

The swing equation M(d²δ/dt²) = Pm − Pe governs the dynamic behavior of the generator's rotor angle during disturbances.

Question 2

An overhead transmission line has a distributed capacitance to ground. Under steady-state AC operation, this capacitance causes the line to:

Accepted Answer

Generate reactive power (leading)

Answer

Shunt capacitance generates leading reactive power (VArs), which can raise voltage levels along the line.

Question 3

A three-phase, 415 V induction motor draws 20 kW at a power factor of 0.8 lagging. What is the reactive power consumed?

Accepted Answer

15 kVAR

Answer

Q = P × tan(θ) = 20 × tan(cos⁻¹0.8) = 20 × 0.75 = 15 kVAR.

Question 4

Which type of DC generator has the best voltage regulation under varying load?

Accepted Answer

Compound generator (cumulative)

Answer

A cumulative compound generator combines series and shunt field effects to maintain nearly constant terminal voltage from no-load to full-load.

Question 5

In symmetrical component analysis, a single line-to-ground (SLG) fault is characterized by:

Accepted Answer

Positive, negative, and zero sequence currents all being equal

Answer

For an SLG fault, all three sequence currents (I1, I2, I0) are equal and the sequence networks are connected in series.

BEE - Bachelor of Electrical Engineering Practice Test