On the basics of electricity transmission – Understanding the fundamentals of how electricity is transmitted

Source: This post on the basics of electricity transmission has been created based on the article “Understanding the fundamentals of how electricity is transmitted” published in The Hindu on 8^th November 2023.

UPSC Syllabus Topic: GS Paper 3 Science and Technology – Developments and their applications and effects in everyday life.

News: This article discusses the mechanism of electricity transmission. It also highlights the factors which determine transmission losses in power transmission.

A Power supply system has 3 broad components:

1. Generation: Electricity is generated at power plants as well as at smaller renewable-energy installations.
2. Transmission: It is transmitted using a distributed network of stations, substations, overhead and underground cables, and transformers.
3. Distribution: Finally, it is distributed to consumers in a standardised way.

A Power Grid performs the above 3 functions.

What is the role of a power grid?

A national power grid includes all 3 components: production, transmission and distribution. Apart from this, it also does the following:

1. Storage of Energy: Grids also have storage facilities that store electrical energy when there’s a surplus supply and release it in times of deficit, such as in the case of renewable energy sources.
2. Manage fluctuations in demand: They also have automated systems which increase or decrease the output of power sources in response to fluctuating consumer demand.
3. Handle emergency situations: They are also connected to sources like gas turbines that can provide power on short notice, such as during emergencies.

How is power transmitted as part of a power grid?

Step I: From a power station, the wires are routed to transformers that step-up (increase) their voltage.

Step II: These wires eventually lead to substations.

Step III: Distribution substations step-down (decrease) the voltage in power lines and prepare them for consumption.

Power Transmission. Source: ElectricalEasy.com

What factors do transmission losses of electricity depend on?

1. Magnitude of Current and Voltage: In any conductor, the transmission efficiency is higher at lower current and higher voltage. For this purpose, transformers are used. They increase the voltage and reduce the current before feeding into transmission lines and do the reverse when receiving current at the consumer-end.
2. Characteristics of wire (Thickness and Cost): The loss of energy through resistance in the wire can be controlled by adjusting the cable’s thickness: the thicker it is, the less energy is lost. However, when the cost of the cable’s material is high, the cables are thinner.
3. Type of current (AC or DC): An alternating current (AC) has higher transmission efficiency (compared to direct current (DC)). AC can be easily stepped up or down in voltage using transformers. Higher voltage AC for the same power transfer helps to reduce resistive losses. In DC systems, voltage conversion is more challenging.
4. Frequency of AC: When the AC frequency is higher, the amount of resistance to current in the wire increases.

What are the challenges of power transmission in India?

1. Aging Infrastructure: Many transmission and distribution lines and equipment in India are old and in need of modernization. This leads to energy losses due to inefficiencies in the system.
2. Overloading and Unbalanced Loading: Overloading transformers and unbalanced loading can lead to technical losses as well as reduce the lifespan of distribution infrastructure.
3. Theft and Pilferage: Unauthorized tapping and theft of electricity is a significant issue in many parts of India.
4. Voltage Fluctuations: Variations in voltage levels can result in energy losses, as excessive voltage can cause appliances to consume more power.
5. Inadequate Investment: Many DISCOMs face financial constraints that limit their ability to invest in modern technology and equipment.

Terminology used:

Insulators: Insulators in contact with the wires draw away some current if there is a surge of current in the line.

Dampers: Dampers prevent vibrations in the wires from affecting the towers’ stability.

Switches: They are used to control the availability of current and to move currents between different lines.

Wide-area synchronous grid: If all the generators connected to a grid are producing an AC current at the same frequency.

Alternating Current: Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time, in contrast to direct current (DC), which flows only in one direction.

Question for practice:

What factors should be considered to reduce transmission losses in power distribution in India?