ELECTRICITY TRANSMISSION

• Power transmission is necessary to move electricity from power plants to consumers.
• Power plants are often located in remote areas, far from where the electricity is needed.
• Transmission lines allow electricity to be transported over long distances with minimal loss.
• Electricity is transmitted using a network of transmission lines, substations, and transformers.
• Transmission lines carry electricity at high voltage, which reduces losses during transmission.
• Substations step up or down the voltage of electricity, depending on the need.
• Transformers convert alternating current (AC) to direct current (DC) and vice versa.
• AC is the most common form of electricity transmission. AC is easier to transmit over long distances than DC because it can be stepped up to a higher voltage, which reduces losses.

3. How is Power Transmitted?

• In a three-phase AC circuit, each wire transmits an AC in a different phase.
• From a power station, the wires are routed to transformers that step up their voltage.
• Then, they are suspended from transmission towers, which must be stable and properly wired, as they travel long distances.
• Insulators in contact with the wires draw away some current if there is a surge in the line; circuit-breakers ‘break’ the circuit if there is too much.
• The towers are also grounded and equipped with arresters that prevent sudden increases in voltage such as due to a lightning strike from affecting the wires.
• Similarly, dampers prevent vibrations in the wires from affecting the towers' stability.
• Switches are used to control the availability of current and to move currents between different lines.

4. How do Grids Operate?

• As mentioned earlier, transmission is situated between production and distribution.
• A national grid includes all three components, and as a result, transmission also has to account for the particulars of power production at different types of sources, at various locations, and how and where that power is consumed.
• For example, some sources like coal-fired or nuclear reactors can produce energy continuously, whereas renewable energy sources are intermittent.
• So grids also have storage facilities that store electrical energy when there's a surplus supply and release it in times of deficit.
• They are also connected to sources like gas turbines that can provide power on short notice, such as during emergencies, as well as automated systems that ‘tell’ sources to increase or decrease their output in response to fluctuating consumer demand.
• Grids also need to respond to failure in different parts of the network and prevent them from carrying over to other parts, adjust voltages in response to demand (as well as manage demand), control the AC frequency, improve the power factor (the power drawn by a load versus the power available in a circuit), etc.
• A grid becomes a wide-area synchronous grid if all the generators connected to it are producing an AC current at the same frequency.
• The world's largest such grid covers Azerbaijan, Belarus, Georgia, Kazakhstan, Kyrgyzstan, Mongolia, and Russia; the world's most powerful is the North Chinese State Grid, with a connected capacity of 1,700 GW.
• India's national grid is also a wide-area synchronous grid. Such grids result in lower power costs but also require measures to prevent cascading power-supply failures.

5. Way Forward

Transmission is a critical component of the modern electricity grid. It is also important to consider the broader context of the energy transition. As the world moves away from fossil fuels and towards renewable energy sources, the role of electricity transmission will become even more important. It will be essential to ensure that the transmission grid is able to accommodate the increasing demand for electricity and that it is able to do so in a way that is reliable, affordable, and sustainable.

Source: The Hindu