|Job Title:||Electrical Supply and Distribution Systems|
|Job Description:||1. For a Yd1 transformer:
(a) draw the connection diagram
(b) show how the connections must be modified to allow parallel operation with a Yd11 transformer
(c) draw a phasor diagram for the modified connection.
2. (a) Two single-phase transformers have the following impedances referred to the secondary side.
Unit A rated 250 kVA (0.09 + j2.7) Ω
Unit B rated 400 kVA (0.04 + j1.6) Ω
Determine the load taken by each machine as a percentage of its rating when they share a common load of 500 kVA at 0.73 p.f. lag.
(b) Transformer A is rated at 300 kVA with an impedance of
(0.09 + j0.18) Ω
Transformer B is rated at 200 kVA with an impedance of
(0.09 + j0.23) Ω
If these transformers are connected in parallel to supply a common
load, determine the percentage overload on B when A supplies its
full load at p.f. 0.45 lag.
3. From the operating chart shown in FIGURE 15 of lesson ESD – 2 – 2,
determine the following performance limitations for a generator:
(a) where the power limit and the MVA limit coincide;
(i) the power factor
(ii) the load angle
(iii) the MVAr output
(b) where the power limit and the stability margin coincide;
(i) the p.u. excitation
(ii) the MVA output.
4. A 3-phase synchronous generator rated at 570 MVA is connected to an
Using the data given in the table below, plot the capacity chart of the