Electrical Power SystemsGuided By: Prof. Yogesh Patel

Prepared By:Nayan solanki-130120109055Vipul solanki-130120109061Kausheel charan-130120109064 Branch : Electrical Engineering

CONTENTS Resistance Bundled Conductor Skin effect Proximity effect

RESISTANCE The resistance of any material with a uniform cross-

sectional area is determined by the following factors: Material Length Cross-sectional Area Temperature

Material and its unique molecular structure will react differently to pressures to establish current through its core. Conductors – Permit generous flow of charge Insulators – Have high resistance

RESISTANCE TEMPERATURE COEFFICIENT

EXAMPLEExample: A platinum resistance thermometer uses thechange in R to measure temperature. Suppose R0 = 50Ω at T0=20 ºC.α for Pt is 3.92×10-3 (ºC)-1 in this temperature range.What is R when T = 50.0 ºC?R = 50Ω [1 + 3.92 ×10-3 (ºC)-1 (30.0 ºC)] = 55.9 Ω

BUNDLED CONDUCTORS It Is a conductor made up of two or more

subconductors and is used as one phase conductor.

For voltages in excess of 230 kV bundled conductors are used.

At these voltages ordinary conductors may cause excessive corona and noise which may affect the communication lines.

Increased corona will result in significant power loss.

Spacers are used to seperate the conductors at regular intervals.

Aerial Bundled Conductor Spacer

SOLID STRANDED CONDUCTOR BUNDLED CONDUCTOR

•Number of small conductors bunched together

Bunch of minimum 2 and maximum 4 conductors

•First layer of strands around the central conductor is 6 then second is about 12 and third is about 18 and so on

•In bundled conductors minimum 2 conductors are there which are joined after regular intervals

•The aimof stranded conductor is to increase the flexibilty of conductor

•The aim of bundled conductor is to increase overall diameter of the conductor so that current carrying capacity is increased

Advantages of bundled conductors:

1.Line resistance is reduced2.Voltage gradient is reduced3.Corona loss is reduced4.Conductor vibration is reduced

Disadvantages of Bundled Conductors:

1.Ice and wind loading is increased2.Spacers are required as the inspection is complicated3.Increased charging kVA

“Skin effect” is the tendency of an alternating electric current (AC) to become distributed within a conductor such that the current density is largest near the surface of the conductor, and decreases with greater depths in the conductor.

The skin effect causes the effective resistance of the conductor to increase at higher frequencies where the skin depth is smaller, thus reducing the effective cross-section of the conductor.

At 60 Hz in copper, the skin depth is about 8.5 mm. At high frequencies the skin depth becomes much smaller

Skin Effect:-

Skin Effect (figure):-

Factors affecting skin effect:

1.Shape of conductor:• stranded conductor has less skin effect and solid conductor has more.

2.Type of material

3. Diameter of the conductors:•skin effect increases with increase in diameter

4.Operational frequency:•Skin effect increases with increase in frequency

PROXIMITY EFFECT It affects the resistance of the line. It is effect on conductor’s magnetic field and

resistance due to proximity of another conductor.

It increases the resistance of conductor .

Proximity effect depends on:•Frequency of the current•Conductor size•Permeability of material