The shown distribution network is to supply two factories A & B with load curves indicated. Assume that both factories have a lagging power factor of 0.8 . Select the required sizes of transformers for both factories such that in the case of a failure in one transformer the overload on the remaining ones should not exceed 15% . ) Select the required sizes of fuses to be installed at both sides of transformers. :) Calculate the annual energy losses in transformers of factory A. Assuming that transformers are in operation continuously . 1) Select the required size of the 11KV. XLPE cables for the distribution network , if cables are to be laid direct in ground with maximum ground temperature of 30º C. e) Calculate the annual energy losses in cables of section SA S 2 Km A 3 Km 11/0.4 KV Trans. 11/0.4 KV Trans. Factory A PF = 0.8 lag. Factory B PF = 0.8 lag. |S (KVA) 500 S (KVA) 500 400 400 300 300 200 200 100 100 Time (hr) 24 Time (hr) 24 12 18 12 18 Load curve of Factory (A) Load curve of Factory (B)

The shown distribution network is to supply two factories A & B with load curves indicated. Assume that both factories have a lagging power factor of 0.8 . Select the required sizes of transformers for both factories such that in the case of a failure in one transformer the overload on the remaining ones should not exceed 15% . ) Select the required sizes of fuses to be installed at both sides of transformers. :) Calculate the annual energy losses in transformers of factory A. Assuming that transformers are in operation continuously . 1) Select the required size of the 11KV. XLPE cables for the distribution network , if cables are to be laid direct in ground with maximum ground temperature of 30º C. e) Calculate the annual energy losses in cables of section SA S 2 Km A 3 Km 11/0.4 KV Trans. 11/0.4 KV Trans. Factory A PF = 0.8 lag. Factory B PF = 0.8 lag. |S (KVA) 500 S (KVA) 500 400 400 300 300 200 200 100 100 Time (hr) 24 Time (hr) 24 12 18 12 18 Load curve of Factory (A) Load curve of Factory (B)

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.44P: A 130-MVA,13.2-kV three-phase generator, which has a positive-sequence reactance of 1.5 per unit on...

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An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
A single-phase 50-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer at the load end of a 2400-volt feeder whose series impedance is (1.0+j2.0) ohm. The equivalent series impedance of the transformer is (1.0+j2.5) ohms referred to the high-voltage (primary) side. The transformer is delivering rated load at a 0.8 power factor lagging and at a rated secondary voltage. Neglecting the transformer exciting current, determine (a) the voltage at the transformer primary terminals, (b) the voltage at the sending end of the feeder, and (c) the real and reactive power delivered to the sending end of the feeder.
The motors M1andM2 of Problem 3.45 have inputs of 120 and 60 MW, respectively, at 13.2 kV, and both operate at unity power factor. Determine the generator terminal voltage and voltage regulation of the line. Neglect transformer phase shifts.
In developing per-unit equivalent circuits for three-phase transformers. under balanced three-phase operation. (i) A common Sbase is selected for both the H and X terminals. (ii) The ratio of the voltage bases Vbase/VbaseX is selected to be equal to the ratio of the rated line-to-line voltages VratedHLL/VratedXLL. (a) Only one of the above is true. (b) Neither is true. (C) Both statements are true.
Consider Figure 3.4. For an ideal phase-shifting transformer, the imda nce is unchanged when it is referred from one side to the other. (a) True (b) False
Reconsider Problem 3.64 with the change that now Tb includes both a transformer of the same turns ratio as Ta and a regulating transformer with a 4 phase shift. On the base of Ta, the impedance of the two comp onents of Tb is jO.1 per unit. Determine the complex power in per unit transmitted to the load through each transformer. Comment on how the transformers share the real and reactive pors.
PowerWorid Simulator case Problem 3_60 duplicates Example 3.13 except that a resistance term of 0.06 per unit has been added to the transformer and 0.05 per unit to the transmission line. Since the system is no longer lossless, a field showing the real power losses has also been added to the oneline. With the LTC tap fixed at 1.05, plot the real power losses as the phase shift angle is varied from 10 to +10 degrees. What value of phase shift minimizes the system losses?
A 130-MVA,13.2-kV three-phase generator, which has a positive-sequence reactance of 1.5 per unit on the generator base, is connected to a 135-MVA,13.2/115Y-kV step-up transformer with a series impedance of (0.005+10.1) per unit on its own base. (a) Calculate the per-unit generator reactance on the transformer base. (b) The load at the transformer terminals is 15 MW at unity power factor and at 115 kV Choosing the transformer high-side voltage as the reference phasor, draw a phasor diagram for this condition. (C) For the condition of part (b), find the transformer low-side voltage and the generator internal voltage behind its reactance. Also compute the generator output power and power factor.
The transformer of Problem 3.16 is supplying a rated load of 50 kVA at a rated secondary voltage of 240 V and at 0.8 posr factor lagging. Neglect the transformer exciting current. (a) Determine the input terminal voltage of the transformer on the high-voltage side. (b) Sketch the corresponding phasor diagram. (c) If the transformer is used as a step-down transformer at the load end of a feeder whose impedance is 0.5+j2.0, find the voltage VS and the power factor at the sending end of the feeder.
Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.
Consider a single-phase electric system shown in Figure 3.33. Transformers are rated as follows: XY15MVA,13.8/138kV, leakage reactance 10 YZ15MVA,138/69kV, leakage reactance 8 With the base in circuit Y chosen as 15MVA,138kV determine the per-unit impedance of the 500 resistive load in circuit Z, referred to circuits Z, Y, and X. Neglecting magnetizing currents, transformer resistances, and line impedances, draw the impedance diagram in per unit.
A single-phase two-winding transformer rated 90MVA,80/120kV is to be connected as an autotransformer rated 80/200kV. Assume that the transformer is ideal. (a) Draw a schematic diagram of the ideal transformer connected as an autotransformer. showing the voltages, currents, and dot notation for polarity. (b) Determine the permissible kVA rating of the autotransformer if the winding currents and voltages are not to exceed the rated values as a two-winding transformer. How much of the kA rating is transferred by magnetic induction?