Normally we perform sag calculation for the normal temperature conditions. However, in practical scenario there are some special cases can occur where the cold climate area and in winter seasons. The wind pressure also got an effect on sag and the length of sag can vary due to this conditions.
So wind pressures and the weight of ice on the conductor also need to take into consideration while performing sag calculation for high voltage power lines.
When the ice coating surrounded by the conductor get to increase the net diameter of the conductor and its weight also get higher.
Application of Wind Pressure and the Ice Load on the Sag Template
Normally the net wind pressure direction is taken into the horizontal direction to the line conductor. The direction of Ice coating and the original conductor weight pressure in the vertical direction. So the total force on the high voltage line conductor is the vertical sum of the horizontal and vertical forces.
So the relevant calculation to calculate the weight of the conductor per unit length area we can use the following equation.
The phase diagram of the weight and pressure applied to the conductor shown in below image
Wt= weight of the conductor per unit length
Wi = Weight of the ice per unit length
Ww= Wind pressure applied per unit length
Sag Calculation under above conditions
The sag equation for transmission line is as following
S =Wtl²/8T
Wt we get the value used in the respect calculation
T – T is considered as working tension and T can represent the ultimate strength divided by the safety factor of the certain conductor.
So by using the mentioned above equations, we can find out the sag of high voltage power line where the special environmental conditions. It is essential to obtain accurate calculation for the design of the high voltage power lines to obtain a sustainable transmission network.
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