Power System Analysis - Introduction

POWER SYSTEM ANALYSIS

INTRODUCTION

Every power system has three major components

^Ø      Generation: source of power, ideally with a specified voltage and frequency

^Ø      Load: consumes power; ideally with a constant resistive value

^Ø      Transmission System: transmits power; ideally as a perfect conductor

Complications

^Ø    No ideal voltage sources exist

^Ø    Loads are seldom constant

^Ø    Transmission system has resistance, inductance, capacitance and flow limitations Simple system has no redundancy so power system will not work if any component fails

Notation – Power

    Power: Instantaneous consumption of energy

    Power Units

    Watts          = voltage x current for dc (W)                   

    kW    –        1 x 10³ Watt                                     

    MW   –        1 x 10⁶ Watt                                     

    GW   –        1 x 10⁹ Watt                                     

    Installed      U.S.   generation   capacity      is       about 900 GW ( about 3 kW per person)

    Maximum load of Champaign/Urbana about 300 MW

Notation – Energy

    Energy: Integration of power over time; energy is what people really want from a power system

    Energy Units

    Joule =       1 Watt-second (J)

    kWh  –        Kilowatthour (3.6 x 106 J)

    Btu    –        1055 J; 1 MBtu=0.292 MWh

Power System Examples

^Ø       Electric utility: can range from quite small, such as an island, to one covering half the continent there are four major interconnected ac power systems in North American, each operating at 60 Hz ac; 50 Hz is used in some other countries.

^Ø       Airplanes and Spaceships: reduction in weight is primary consideration; frequency is 400 Hz.

^Ø       Ships and submarines

^Ø       Automobiles: dc with 12 volts standard

^Ø       Battery operated portable systems