Electrical Power System SMJE 2103 Electrical Power Delivery System
Power Flow / Load Flow A numerical analysis for future planning of operational power system in order to optimize generated power. The objective is to produce following inform: i- voltage magnitude and phase angle at each bus ii- real and reactive power flowing in each element iii- reactive power loading on each generator
Problem Statement For a given power network, with known complex power loads and some set of specification or restrictions on power generation and voltages, solve for any unknown bus voltage and unspecified generation and finally for the complex power flow in the network components.
Network Structure
Load Flow Solution There are four quantities of interest with each bus: Real Power Reactive power Voltage magnitude Voltage angle At every bus of the system, two of these four quantities will be specified and the remaining two will be unknowns. Each of the system buses may be classified in accordance with which of the two quantities are specified.
Power Delivery “Overhead Lines - Components”
Power Delivery “Towers - types”
Power Delivery “Towers - size” Height of tower is determine by- h1=Minimum permissible ground clearance h2=Maximum sag h3=Vertical spacing between conductors h4=Vertical clearance between earthwire and top conductor
Power Delivery “Conductor - types” ACSR Conductor(Aluminium Conductor Steel Reinforced) AAC(All Aluminium Conductor) AAAC(All Alloy Aluminium Conductor)
Power Delivery “Line – equivalent circuit” L’ = Inductance R’ = Resistance C’ = Capacitance G’ = Leakage Resistance
Power Delivery “Conductor - resistance” Short line (up to 80 km) Medium-length lines (up to 240 km) Long line (above 240 km)
Power Delivery “Transmission Line – Single Line”
Power Delivery “Transmission Line”
Power Delivery “Power Cable”
Power Delivery “Power Cable”
Power Delivery “Power Cable - losses”
Power Delivery “Power Cable - losses” Dielectric used for cable insulation must have following properties: High insulation resistance High dielectric strength Good mechanical strength Immune to attack by acids and alkali in the range 0-100o C Should not be too costly Should no be hygroscopic (tending to absorb water), or if hygroscopic should be enclosed in a water tight covering
Power Delivery “Cable - resistance”
Power Delivery “Cable - inductance”
Power Delivery “3- Core Cable - inductance”
Power Delivery “3- Core Cable – inductance (M & C)”
Power Delivery “3- Core Cable – inductance” (Measured)
Power Delivery “3- Core Cable - inductance” (Measured)
Example A 3 core, 3 phase metal sheathed cable on testing for the capacitance gave the following result; Capacitance between all conductors bunched and sheath, Cm1 = 0.6 F Capacitance between two conductors bunched with sheath and third conductor, Cm2 = 0.36 F With the sheath insulated, find; Capacitance between any two conductor Capacitance to neutral Charging current if the cable is connected to 11 kV, 3 phase, 50 Hz system
Power Delivery “3- Core Cable – Gas-pressure”
Power Delivery “3- Core Cable – Gas-pressure”
Power Delivery “3- Core Cable – Gas-pressure”
Power Delivery “Insulator”
Power Delivery “Insulator - Types” There are several types of insulators but the most commonly used are : Pin Insulator Suspension Insulator Strain Insulator and Shackle insulator.
Power Delivery “Pin Insulator” - Nonconducting material such as porcelain, glass, plastic, polymer, or wood. - Upto 33 kV
Power Delivery “Pin Insulator”
Power Delivery “Suspension Insulator” - For high voltages (>33 kV) - Each unit or disc is designed for low voltage, say 11 kV - The number of discs in series would obviously depend upon the working voltage
Power Delivery “Suspension Insulator”
Power Delivery “Strain Insulator” - Dead end of the line or corner or sharp curve. - For low voltage lines (< 11 kV). - Two or more strings are used in parallel.
Power Delivery “Strain Insulator”
Power Delivery “Shackle Insulator” - Used for low voltage distribution lines. - Horizontal or vertical position.
Power Delivery “Shackle Insulator”
Power Delivery “Insulator”
Power Delivery “Circuit Breaker”
Power Delivery “Circuit Breaker”
Power Delivery “Circuit Breaker”
Power Delivery “Circuit Breaker”
Power Delivery “Circuit Breaker”
Power Delivery “Switchgear (GIS)”
Power Delivery “Switchgear (GIS)”
Power Delivery “Switchgear (GIS)”
Power Delivery “Switchgear (GIS)”
Transmission-Lines Design There are some factors should be considered in designing transmission lines for new power-system planning to meet future system requirement of load growth and new generation: Electrical factors Mechanical factors Environmental factors Economics factors Discuss the factors in detail.