Electrical Plus Notes

Sag Template  1) Sag template is used for allocating the position and height of the supports correctly on the profile.  2) The sag template is usually made up of transparent celluloid, perplex, or somtimes cardboard. 3) Sag template defines the limit of minimum clearance angle between the sag and the ground for safety purpose. Curves marked on the sag template are : 1 ) Hot template Curve or Hot Curve 2 ) Ground Clearance Curve 3 ) Support Foot or Tower Curve 4 ) Cold curve or Uplift Curve                                fig : 1 ( Note : Above image is enlarged in fig 2 )                                    fig : 2 Hot Curve :  The hot curve is obtained by plotting the sag at maximum temperature against span length. It shows where the supports must be located to maintain the prescr...

CONTENTS > Line Supports : > Properties for LIne Supports : > Types of Line Supports : > Advantages and Disadvantages of Line Supports : Line Supports Line support palys a major role in power transmission. Line support (like Poles and Towers) are used for supporting the overhead lines or wires. Desired properties for lIne Supports:   1) High mechanical strength to withstand the weight of conductors and wind load etc 2) Light in weight without the loss of mechanical strength. 3) Cheap in cost and economical to maintain. 4) longer life. 5) Easy accessibility of conductors for maintenance. Line Supports Types:   1) Wooden Poles 2) Steel Poles 3) R.C.C. Poles 4) Lattice steel towers   1) Wooden Poles :   These supports are cheap, easily available , provide insulating properties and widey used for distribution purpose in rural areas.  # Span upto 50 meters. # Made of seasoned wood (sal and chir)   Advantages  1)...

CONTENTS > Sag in Transmissison Line :  > Span between Supports : > Tension in Conductor :  > Formula for sag calculation : > Factors affecting sag : > Effect of ice loading on sag : > Effect of wind pressure on sag  : What is Sag in Transmission Line ? Sag in conductor : When the conductors are supported at the towers or poles, they are pulled and connected between supports but soon conductors will sag or dip under its own weight.   Maximum sag is essential in determining the ground clearance of the conductor. The sag should be minimum in order to reduce the conductor material and to avoid extra height of pole. Span :  The distance between adjacent supporting towers is called span.  Tension in conductor :  To avoid the mechanical faiilure of the conductor the tension in the conductor should be low. The tension in conductor depends upon conductor weight, effect of temperature, ice and wind loading.   So ...

CONTENTS > Properties of Good Conductor > Types of conductors used in Overhead Transmision Lines A Conductor is one of the most important component of overhead lines. Proper selection of coductor is as important as selection of size and voltage .     Properties required for a good conductor : a) HIgh electrical conductivity b) High tensile strength  c) Lower cost  d) Corrosion resistive e) Light in weight  Types of Conductors used for Transmission Lines Following are four common types of overhead conductors that are used for overhead transimission and distribution to carry generated power from generating stations to the end users. 1) AAC : All Aluminium Conductor 2) AAAC : All Aluminium Alloy Conductor 3) ACSR : Aluminium Conductor Steel Reinforced 4) ACAR : Aluminium Conductor Alloy  Reinforced AAC :-  (a) All Aluminium Conductor is also called as Alumunuim Stranded Conductor.   (b) It has conductivity about 61% IACS( In...