Category Physics

          Electric power transmission means the transfer of electric power from one place to another in large quantities.

           Typically, this happens between a power plant and a substation situated near a populated area. A substation is where voltage is transformed from high to low or vice versa using transformers. When power is transmitted from substations to consumers, the process is called power distribution. Normally, transmission takes place at very high voltage, like 110 kV or above. This is, because of the large amount of power involved in this.

            Over long distances, electricity is transmitted through overhead power transmission lines. But in places that are environmentally sensitive, or where there is very high population, transmission takes place underground. They have high installation cost and operational limitations, yet their maintenance cost is lower.

               The network of power stations, transmission lines, and substations is together known as a transmission grid. 

        From the moment power is generated in a plant, it goes through various stages before reaching our homes.

         Let’s see how power travels. From the electricity generating plants, current is sent through transformers to increase the voltage, so that it can be pushed longer distances.

         Electric power then reaches a substation. Here, the voltage gets lowered, so that it could be sent to smaller power lines.

         From there, it travels through various distribution lines, and reaches your neighbourhood where smaller transformers reduce the voltage, so that you can take safe power to your homes.

        From the transformer, power is carried through service drops, or smaller overhead electrical lines to your homes. It also passes through the ‘meter’ installed in the house that can measure how much power is used by the family.

        The current moves straight to the service panel, where fuses protect the wires inside the house from overloading. Keep in mind that children should never touch this panel!

         It is from here that power finally moves to the switches and outlets all over the house.

       Overhead power lines are structures for electric power transmission and distribution across large distances. They also make the cheapest method for transmitting power.

         In usual cases, overhead power lines have one or more conductors suspended by towers. One of the major duties of these power lines is to maintain enough space or clearance between these energized conductors and the ground, in order to avoid danger.

           These days, power lines can be operated at voltages of 765,000 volts or even more, between conductors. Depending on their range of voltages, overhead power lines can be classified as low voltage, medium voltage, high voltage, extra high voltage, and ultra high voltage.

              However, these power lines are extremely dangerous, and one has to keep a safe distance from them. Unlike household power cords, overhead power lines are not insulated. Even if it looks like insulation, it might be a weatherproofing material. 

       A transformer is an electrical device that transforms electricity from high to low voltage and vice versa. It is an important component for power transmission. Let’s get to know why.

       We saw the process through which electric power reaches our homes. When electricity travels from a power plant, it comes in a very high voltage. This is because the voltage from the plant is ‘stepped up’ by transformers before they are transmitted.

       The voltage has to be increased because electric power has to travel very long distances, and that too, with minimal loss of energy. We should know that energy is lost in the process of power transmission. But if the voltage is high, energy loss would be low.    

        But do our homes need this kind of voltage? Absolutely not! Before the power reaches houses, the voltage has to be lowered, or stepped down. This is where transformers again become important. They step down voltage from high to low. 

         Electric meters are devices that we commonly see in houses and offices. They are used to measure the total electrical energy consumed by the appliances in a house or office. The devices are installed by the electric power company that supplies electricity.

          If you take a close look at these meters, you can see a few digits. They denote the number of units of electricity that has been consumed so far. Our electricity bill depends totally on this reading.

          There are different types of electric meters available in the market. One is the electro-mechanical meter, which is most commonly used in our country. It has a magnetic metallic disc attached, which rotates, depending on the power passing through it. The rate of this rotation decides the reading on the meter.

          Then there are electronic meters that are popular in cities. In these, readings appear digitally on the display fixed on the meter.

          The newest in this league is the smart meter. They are electronic meters, but they have an added advantage. These smart meters are connected back to the utility (which provides us electricity) through the internet. Hence, no official will have to come in person and take the readings. The readings are sent through the internet, which makes the job easier. 

Electric power is always represented in terms of watts (W) or kilowatts (kW). A thousand watts together make a kilowatt.

Watts describe the rate at which electricity is consumed during a specific period. Take the case of a 15-watt LED bulb. It draws 15 watts of power at any moment when turned on.

Let’s look at other examples to understand the concept better. The power rating of a typical incandescent light bulb used in houses is between 25 to 100 watts. To produce a similar amount of light, fluorescent lamps consume 5 to 30 watts, and LED lamps use 0.5 to 6 watts.

Coming to power stations, a typical power station that uses coal to generate electricity produces around 600 to 700 megawatts. A megawatt is equivalent to one million watts! The term ‘watt’ was named after James Watt who developed the steam engine. Watt-hour is quite different from a watt. It is a measure of electrical energy equivalent to a power consumption of one watt for one hour.