The power grid is the network that carries electricity from a power plant to every home, shop and factory. It is often called the largest machine ever built. A small part of it sits in your home: the electricity meter.
Electricity reaches you in three stages. In generation, power plants make the electricity. In transmission, high-voltage lines carry it over long distances, because high voltage loses less power on the way. In distribution, a substation lowers the voltage, and local lines carry the power to homes, shops and factories. The machines that change the voltage, and the switches that cut the power during a fault, are power transformers and switchgear. A transformer changes voltage easily only when the current is alternating current, which is one reason the grid uses AC.
The grid has one hard rule: the power put in must equal the power taken out, every second. Electricity cannot be stored cheaply in large amounts, so the balance has to be kept live. If the two drift apart, equipment trips and whole areas lose power. Keeping them equal is called grid balancing. Operators do it from a control room, using an energy management system that shows the whole network on screen. The sensors, meters and control software that watch and steer the grid are often called its nervous system.
Imagine it is 7 pm on a hot evening in Nagpur. You switch on the fan, and so do lakhs of other people within a few minutes. The control room sees demand rising and asks power plants to produce more. At your door, a smart meter records how much power your home uses and sends the readings over a network, so nobody has to visit. Software called energy disaggregation can later tell you how much of your bill came from the fan and the air conditioner.
The buyers of all this technology are the companies that run the grid and sell electricity. In India, the ones that supply homes are called distribution companies, or discoms. Most are owned by state governments, and they buy through government tenders. Discoms want smart meters because they lose a lot of money to theft and to unpaid bills.
Power used to travel in one direction, from large plants to homes. Now rooftop solar panels, batteries and car chargers sit at the grid edge, and some of them send power back. Software such as a virtual power plant adjusts thousands of them together. A tree near a power line can also cause a power cut, so utilities use vegetation management to find the risky trees.