It is unnecessary to insulate the high voltage package, and it is also a waste of money.
The transmission voltage of high-voltage transmission lines is mostly above 10 thousand volts, and the voltage of some lines is as high as 100 thousand volts and 500 thousand volts. If such lines are to be insulated, the insulation thickness of ordinary wires is far from enough. At ordinary times, the voltage of the wires in our home is only 220V V. As long as we wrap them with a thin insulating layer to prevent people from contacting the live wire, we can prevent electric shock. But high-voltage equipment is different. People standing at a certain distance next to high-voltage equipment will still get an electric shock even if they don’t touch it.
Electric shock caused by high voltage can be divided into two types: step voltage electric shock and high voltage arc electric shock.
Step-by-step voltage electric shock means that if the high-voltage transmission line falls on the ground and a current flows into the ground, the potential near the grounding point will gradually decrease in the distance, so there is a voltage difference where people stand with their feet, and the current flows through the human body to cause electric shock, which is called step-by-step voltage electric shock.
Step voltage electric shock
High-voltage arc electric shock is that when people get close to high-voltage equipment to a certain distance, they will produce arc discharge, that is, you will see a flash of light for a moment, and then the electric shock person will be knocked down by high voltage and injured or even killed. High voltage arc electric shock
Therefore, it is not enough to just wrap a layer of insulation for high-voltage transmission lines. According to the calculation that the safe distance of high-voltage lines touching people is one millimeter per 3000 volts, the insulation layer thickness of 500,000 volt lines must reach at least 17cm. Such a thick insulation layer is bound to greatly increase the weight of transmission lines, so for a transmission line that is thousands of kilometers long, the cost investment will definitely increase exponentially.
In fact, the easiest way to keep high-voltage lines from harming people is to keep the lines at a certain distance from people, so that people can’t get close to the lines and naturally they won’t cause electric shock accidents. For example, if the transmission line is erected high with a high-voltage iron tower, people will not get an electric shock when walking under the high-voltage line, so there is no need to coat the line with insulation. This method is called "air insulation" in the industry.
Of course, there are also high-voltage lines covered with insulation, which we call high-voltage cables. High-voltage cables are generally used in areas that are not suitable for building overhead lines, such as underground laying. Besides a thick insulating layer, the high-voltage cable is made of copper core, so the cost of high-voltage cable is more than 10 times that of ordinary overhead lines. Unless absolutely necessary, this method will not be adopted.