When electricity is transmitted through cables, a part of it is converted into heat. 
The more heat is generated during transportation, the less usable energy reaches the users. To reduce losses, electricity is transported in high voltage. Transformers convert alternating current produced by generators, to alternating current of very high voltage (several thousands Volts). This very high voltage current is more suitable for transportation over long distances, because fewer losses (heat) occur.
The more heat is generated during transportation, the less usable energy reaches the users. To reduce losses, electricity is transported in high voltage. Transformers convert alternating current produced by generators, to alternating current of very high voltage (several thousands Volts). This very high voltage current is more suitable for transportation over long distances, because fewer losses (heat) occur. The electricity at high voltage can strike even from a distance, under certain conditions. That is why in these columns of PPC, often a sign saying "caution high voltage" is seen.
When the current reaches the point of use, that means our homes (factories are another user category) should be converted to low voltage 220-240 Volt (110 for some other countries). If you notice the pillars of PPC, you will see that not all of them are the same. Some of them have on their top some strange devices which make noise. These devices are transformers that convert high voltage energy coming from the electricity production factory in electricity suitable for domestic use (suitable for our homes).
