EE2303 TRANSMISSION AND DISTRIBUTION Lecture Notes for EEE - Fifth (5th) semester
EE2303 Lecture Notes
UNIT I INTRODUCTION
Structure of electric power system - different operating voltages of generation, transmission and
distribution – advantage of higher operating voltage for AC transmission.
An introduction to EHV AC transmission, HVDC transmission and FACTs.
Mechanical design of transmission line between towers – sag and tension calculations using
approximate equations taking into account the effect of ice and wind.
UNIT II TRANSMISSION LINE PARAMETERS
Parameters of resistance, inductance and capacitance calculations - single and three phase
transmission lines - single and double circuits - solid, stranded and bundled conductors -
symmetrical and unsymmetrical spacing – transposition of lines - concepts of GMR and GMD - skin
and proximity effects - interference with neighbouring communication circuits.
Corona discharge characteristics – critical voltage and loss.
(Simple diagrams of typical towers and conductors for 400, 220 and 110 kV operations)
UNIT III MODELLING AND PERFORMANCE OF TRANSMISSION LINES
Transmission line classification - short line, medium line and long line - equivalent circuits – Ferranti
effect - surge impedance, attenuation constant and phase constant - voltage regulation and
transmission efficiency - real and reactive power flow in lines – power circle diagrams – shunt and
An introduction to power angle diagram - surge-impedance loading, loadability limits based on
thermal loading; angle and voltage stability considerations.
UNIT IV INSULATORS AND CABLES
Classification of insulators for transmission and distribution purpose – voltage distribution in insulator
string and grading - improvement of string efficiency.
Underground cables - constructional features of LT and HT cables – insulation resistance,
capacitance, dielectric stress and grading – tan δ and power loss - thermal characteristics.
UNIT V SUBSTATION, GROUNDING SYSTEM AND DISTRIBUTION SYSTEM
Classification, functions and major components of substations.
Bus-bar arrangements - substation bus schemes - single bus, double bus with double breaker,
double bus with single breaker, main and transfer bus, ring bus, breaker-and-a-half with two main
buses, double bus-bar with bypass isolators. Importance of earthing in a substation. Qualitative
treatment to neutral grounding and earthing practises in substations. Feeders, distributors and
service mains. DC distributor – 2-wire and 3-wire, radial and ring main distribution. AC distribution –
single phase and three phase 4-wire distribution.
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