Power System Analysis I

(a) What are differences between conventional and non-conventional sources of energy? Draw a schematic diagram of one of the power generating stations with non-conventional sources. [2+4] (b) An insulator string for $66\text{ kV}$ line has $4$ discs. The shunt capacitance between each joint and metal work is $10\%$ of the capacitance of each discs. Find the voltage across the different discs and string efficiency.

(a) Define dielectric stress. Determine the expression for the maximum and minimum dielectric stress points in a single core cable when used in voltage $V$. [2+6] (b) Write down the common types of insulators used in overhead transmission and distribution lines. An insulator string for $66\text{ kV}$ line has 4 discs, the shunt capacitance between each joint and metal work is $10\%$ of the capacitance of each disc. Find the voltage across the different discs and string efficiency.

(a) Classify transmission line model. Find A,B,C,D parameters of short transmission line and also draw it phasor diagram with lagging and leading power factor of the load. [2+4] (b) A 3-phase 132 kV, 50 Hz overhead line delivers 50 MVA and pf 0.8 lagging at its receiving end. The constant of the line are $A=0.98\angle 3^{\circ }$ and $B=110\angle 75^{\circ }\Omega$ phase. Find (i) sending end voltage and power angle (ii) sending end active and reactive power (iii) line losses.

(a) What are major electrical components in power station? Draw its schematic diagram and explain in brief. [3+5] (b) Derive the expressions for series impedance ($Z^{\prime }$) and shunt admittance ($Y^{\prime }$) parameter of equivalent 'Tee' and 'Pi' of long lines.

(a) Why do transmission line perform as source and sink of reactive power? What are their effects on power system? [3+3] (b) A 3-phase, 50 Hz 100 km long overhead line has the following line constants: resistance per phase per km = $0.153\Omega ,inductance$ per phase per km = $1.21\text{ mH},Capacitance$ per phase per km = $0.00958\mu \text{F}$. The line supplies a load of 20 MW at 0.9 power factor lagging at a line voltage of 110 kV at the receiving end. Calculate the regulation and efficiency.

(a) What do you mean by surge impedance loading (SIL)? At what condition of SIL of line needed reactive power compensation? Explain in brief about compensation. [2+2+4] (b) A single-phase $50\text{ Hz}$ generator supplies $a^n$ inductive load of $5,000\text{ kW}$ at a power factor of $0.707$ lagging by means of $a^n$ overhead transmission line $20\text{ km}$ long. The line resistance and inductance are $0.0195\Omega$ and $0.63\text{ mH}$ per km. The voltage at the receiving-end is required to be kept constant at $10\text{ kV}$. Find (i) the sending-end voltage and voltage regulation of the line; (ii) the value of the capacitors to be placed in parallel with the load such that the regulation is reduced to $50\%$ of that obtained in part (i); and (iii) compare the transmission efficiency in parts (i) and (ii)