One-line diagram of a power system is shown below. Relevant details are mentioned below. Generator: 100 MVA, 11 kV, 3-phase, reactance 20%; Transformer T1: 100 MVA, 10/132 kV, reactance 6%; Transformer T2: 80 MVA, 132/10 kV, reactance 5%; Line reactance is 100 Q. Motors M1 and M2 are rated at 50 MVA and 40 MVA respectively both at 10 kV and 20% reactance. In the above, reactances are per-phase values. Taking generator rating as base, draw the per- phase impedance diagram in which the elements need to be expressed in per unit. * T1 T2 Transmission Line G M,) A m

Subject name: Power System Protection

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OR e) Explain the following protection schemes of alternators. i) Stator inter turn protection. ii) Merz price protection.

explain why Transformers are necessary in all stages of power distribution systems. Three-phase voltages may be stepped up or down by three-phase transformers

urgent required.

2.5.3 A three phase power system has two generator connected in parallel to a transformer and subsequently to a 230 kV transmission line. The ratings for the components are given as below: Generator 1:10 MVA, reactance of 12%. Generator 2: 5 MVA, reactance of 8%. Transformer: 15 MVA, reactance of 6% Transmission line: impedance of 4+j60 2, for which the reactances in percentage are based on the ratings of the respective components. Obtain the reactance and impedance values of the components in the system in percentage, based on 15 MVA and rated voltage of the components.

1. A single-phase power system as shown in Figure 1 consists of a 240 V, 60 Hz generator supplying a load, Zod = 8 + j6 Q through a transmission line of impedance, Zne = 0.08 + j0.14 Q. Answer the following questions: (1) transformer, T; and T2. Determine the voltage at the load and transmission line losses without the (ii) Determine the voltage at the load and transmission line losses with the transformer, T, and T2. T1 T2 1:10 10:1 IG Zaine Zioad source Figure 1

A 4-bus three-phase power system consists of the following equipment: • Generator 1 connected to bus 1 with a rated power of 20MVA, rated voltage of 20 kV, and a series reactance of 0.4 p.u. • Generator 2 connected to bus 5, with a rated power of 12MVA, rated voltage of 10 kV, and a series reactance of 0.3 p.u. Transformer 1 connected between buses 1 and 2, is wye-wye connected with a rated power of 20 MVA, rated voltages 20/100 kV, and a series reactance of 0.1 p.u. • Transformer 2 connected between buses 4 and 5, is wye-wye connected with a rated power of 12 MVA, rated voltages 12/110 kV, and a series reactance of 0.15 p.u. • Transmission Line 2-3 connects buses 2 and 3 and had a series impedance of 50 + j75 ohms. • Transmission Line 3-4 connects buses 3 and 4 and had a series impedance of 40 + j80 ohms. • Load A connected to bus 3 and abosorbes20 MW and 10 MVAR. The voltage at bus 3 is 105 kV. 1) Draw the one-line diagram for the system. 2) Draw the per-unit, per phase…

EX3 Voltage Sag 400 V network short circuit power is 1000 kVA (reactive). A 10 kW induction motor is connected. The motor takes 6-times nominal current when started (assume inductive current). Calculate the voltage drop as a) per unit value, b) per cent value, c) volts in line voltage, d) volts in phase voltage.