




POWER SYSTEM PERFORMANCE
Group A
An overview of modern power system: Layout of typical power system—generating station,
substation, transformer, transmission line, distribution, load. Symbols and circuit
representation of various components of the system. Single line diagram.
Per unit method of calculation: Base quantities and per unit values, modification of per unit
values due to change of base, equivalent circuit of transformer on per unit basis, choice of
base quantities for power system analysis, advantages of per unit method of calculation, per
unit impedance diagram of a power system.
Symmetrical components: Transformation of voltage, current and impedance to symmetrical
component system, complex power in terms of transformed voltage and currents, positive,
negative and zero sequence impedances of different power system components; equivalent
circuits in terms of symmetrical component quantities, advantage of symmetrical component
representation.
Fault studies: Symmetrical threephase fault calculation, fault MVA and circuit breaker
capacity, current limiting reactor, their placement and usefulness.
Unsymmetrical faults, classification, analysis of LG, LL and LLG fault using symmetrical
components, equivalent circuit for representation of different kinds of faults, calculation of
fault current and postfault voltages. Arcing ground, its consequences and remedy.
Load flow study: The basic load flow problem and its importance, classification of system
bus bars, formulation of load flow equations using bus admittance matrix, tteiative solution of
load flow equations by GaussSeidel method, acceleration for convergence.
Economic load despatch: Generation cost, incremental cost, optimal loading of generators on
a common bus bar, transmission loss formula, incremental transmission loss, generation
scheduling taking care of transmission loss.



Group B
High voltage d.c. transmission: Historical review, merits and limitations of d.c. transmission,
kinds of d.c. links, constitution of d.c. links, terminal equipment transformer, converter,
choke and filter; gate control and operation of threephase thyristor bridge as rectifier and
inverter, relationship between input and output voltage and current in the bridge convener,
active and reactive power; control of current andvoltage in a d.c. link, backtoback
connection and its usefulness.
Power system control: Automatic load frequency and voltage control, speed governor, load
sharing among synchronous generators, exciter, brushless excitation system.
Power system stability: Transient power output of a synchronous machine, effect of voltage
regulator and governor on enhancement of transient stability. The swing equations in multimachine
system,
numerical
method
of solution
of swing equations and assessment
of
transient
stability.
Power system protection: Electromagnetic relays,
construction and operating principle of attracted armature, induction disc and induction cup
type relay, inverse time lag relay, plug setting and time setting arrangement.
Overvoltage, overcurrent, earth fault and neutral displacement protection. Primary and
backup protection, coordination of overcurrent relays in radial feeder protection, directional
overcurrent relay, ring main and parallel feeder protection.
Distance protection for transmission lines, three zone protection, tripping circuit, impedance
setting for earth fault and phase fault types relays. Errors in distance measurement, arcingfault, power swing, directional, reactance, mho, ohm and quadrilateral characteristics.
Differential protection schemes for generator and transformer, other protections of generator
and transformer.
Pilot wire relays for feeders and cables, carrier relaysblocking and intertripping schemes,
carrier equipment, carrier phase comparison.







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