EPTD Tutorial 1
Electric Power Transmission and Distribution
Tutorial 1
1. A three-phase, star-connected synchronous generator is rated at 1600kVA
and 13.5kV with X= 30Ω per phase. Calculate percentage of voltage
regulation (%VR) for a load of 1280kW at power factor (pf) of:
(a) 0.8 leading, (b) unity, and (c) 0.8 lagging.
(Answers: -13.2%, 2.19%, 17.74%)
2. Repeat problem 1 if the generator has an impedance of Z = 1.5 + j30 Ω
per phase.
(Answers: -11.9%, 3.2%, 18.62%)
3. The current drawn from a three-phase, star-connected 11kV synchronous
generator is 60A (X= 30Ω per phase). Find the power delivered at the
terminal of the generator and the induced electromotive force E for power
factors of 0.8 leading and lagging. Also, find the corresponding power
angles.
(Answers: 914.5kW, 5464.1<15.28o, 7569.1<10.97o per phase)
4. A three-phase, star-connected synchronous generator is connected to a grid
bus of 12kV and X= j5Ω per phase. The magnitude of the generated emf
(E) equals the magnitude of the bus voltage and the machine delivers
18MW to the grid. Find: (a)δ, (b) current, (c) reactive power at the terminal
(magnitude and direction), and (d) draw phasor diagram.
(Answers: 21.15o, 508.6A<10.57o (leading), 640kVAR (absorbing))