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...

CONTENT > Vibrations in Overhead Conductors > Types of Vibrations >  Precautions Vibrations in Overhead Conductors Vibration is one of the serious cause of conductor failure (i.e. having cracks , breaking of conductor , or flash over ) in overhead conductors of transmission lines. So, vibration should be kept within limits for safe operation of the transmission lines.  Types of Vibrations  Vibration in Power Lines can be categorized into three types caused under the influence of wind :  i) Resonant or Aeolian Vibration  ii) Galloping  iii) Simple swinging i) Aeolian Vibration  1) These vibrations are caused by aerodynamic forces generated as the wind blows across the conductor.       fig : Damage due to Aeolian vibration 2) The frequency of the vibration may receive a positive feedback from the conductor's natural vibration frequency.  3) This self- exciting vibration can cause cracks on the conduct...