1

GATE EE 2011

MCQ (Single Correct Answer)

+2

-0.6

Two generator units $$G1$$ and $$G2$$ are connected by $$15$$ $$kV$$ line with a bus at the mid-point as shown below

$${G_1} = 250\,\,MVA.\,\,\,15kV,\,\,$$ positive sequence $$X = 25$$% on its own base

$${G_2} = 100\,\,MVA.\,\,\,15kV,\,$$ positive sequence $$X = 10$$% on its own base

$${L_1}$$ and $${L_2}$$ $$= 10$$ $$km,$$ positive sequence $$ X = 0.225$$ $$\,\,\Omega /km$$

$${G_1} = 250\,\,MVA.\,\,\,15kV,\,\,$$ positive sequence $$X = 25$$% on its own base

$${G_2} = 100\,\,MVA.\,\,\,15kV,\,$$ positive sequence $$X = 10$$% on its own base

$${L_1}$$ and $${L_2}$$ $$= 10$$ $$km,$$ positive sequence $$ X = 0.225$$ $$\,\,\Omega /km$$

For the above system, the positive sequence diagram with the p.u values on the $$100$$ $$MVA$$ common

2

GATE EE 2010

MCQ (Single Correct Answer)

+2

-0.6

For the power system shown in the figure below, the specifications of the components are the following:

$$G1: 25$$ $$kV,$$ $$100$$ $$MVA,$$ $$X=9$$%

$$G2: 25$$ $$kV,$$ $$100$$ $$MVA,$$ $$X=9$$%

$$T1: 25$$ $$kV/220$$ $$kV,$$ $$90$$ $$MVA,$$ $$X=12$$%

$$T2: 220$$ $$kV/ 25$$ $$kV,$$ $$90$$ $$MVA,$$ $$X=12$$%

$$Line$$ $$1: 220$$ $$kV,$$ $$X= 150$$ $$ohms$$

$$G1: 25$$ $$kV,$$ $$100$$ $$MVA,$$ $$X=9$$%

$$G2: 25$$ $$kV,$$ $$100$$ $$MVA,$$ $$X=9$$%

$$T1: 25$$ $$kV/220$$ $$kV,$$ $$90$$ $$MVA,$$ $$X=12$$%

$$T2: 220$$ $$kV/ 25$$ $$kV,$$ $$90$$ $$MVA,$$ $$X=12$$%

$$Line$$ $$1: 220$$ $$kV,$$ $$X= 150$$ $$ohms$$

Choose $$25$$ $$kV$$ as the base voltage at the generator $$G1,$$ and $$200$$ $$MVA$$ as the $$MVA$$ base. The impedance diagram is

3

GATE EE 2006

MCQ (Single Correct Answer)

+2

-0.6

A generator is connected through a $$20$$ MVA, $$13.8/138$$ kV step up transformer, to a transmission line. At the receiving end of the line a load is supplied through a step down transformer of $$10$$ MVA, $$138/69$$ kV rating. A $$0.72$$ p.u. load, evaluated, on load side transformer ratings as base values of $$10$$ MVA and $$69$$ kV in load circuit, the value of the load (in per unit) in generator circuit will be

4

GATE EE 2004

MCQ (Single Correct Answer)

+2

-0.6

A new generator having $${E_g} = 1.4\,\angle {30^ \circ }\,$$ pu [ equivalent to ($$1.212 +j$$ $$0.70$$)pu ] and synchronous reactance $$'{X_s}'$$ of $$1.0$$ pu on the system base, is to be connected to a bus having voltage $${V_t}$$ in the existing power system. This existing power system can be represented by Thevenin's voltage $${E_{th}} = 0.9\angle {0^ \circ }\,\,$$ pu in series with Tjhevenin's impedance $${Z_{th}} = 0.25\angle {90^ \circ }\,\,$$ pu. The magnitude of the voltage $${V_t},$$ of the system in pu will be

Questions Asked from Per Unit System (Marks 2)

Number in Brackets after Paper Indicates No. of Questions

GATE EE Subjects

Electric Circuits

Electromagnetic Fields

Signals and Systems

Electrical Machines

Engineering Mathematics

General Aptitude

Power System Analysis

Electrical and Electronics Measurement

Analog Electronics

Control Systems

Power Electronics