What is a power grid?

The most important task after the electricity generation is the transmission to consumers or customers. Electricity is transmitted to its consumers via electrical grids or power grids. Power grids are the network of wires, transmission lines, and equipment for electricity delivery from producers to customers. Power grids are intricate systems having dedicated designs and they stretch thousands of kilometers, covering different states, countries, and even continents. The power grid operates at high voltage and generally uses a three-phase alternating current (AC), that enables efficient long-distance electricity transmission. It also enables the power rating to remain near-constant without many fluctuations.

In the earlier days, power generation firms majorly relied on non-renewable energy sources for electricity production, but with growing concern about environmental damage, renewable energy resources have become the major source of electricity production in recent years. Renewable sources such as hydropower energy, which mostly uses the energy of flowing water from rivers, such as the Mississippi River, is one of the primary sources of power generation in the modern age. The power grids can be located near these renewable energy sources.

Besides efficient power transmissions, power grids have a high possibility of intrusion attacks and damage caused by natural disasters. The hurricane, Ida, which made its landfall in August 2021, has caused total damage of $65.25 billion. It was the fifth-strongest storm in the history of the U.S., and it knocked down eight high-voltage electric grid lines and poles that supply electricity to New Orleans. A dedicated search-and-rescue operation was carried out to account for the casualties in the hard-hit areas. Due to the destruction of mobile connectivity, people used walkie-talkies for communications. To tackle intrusion attacks, most electrical grid firms install electric grid security systems. These systems include cameras, high-voltage fences, theft detection alarms, and so on.

Components of power grids

Electricity generators

The electricity generator systems consist of a number of AC generators that are usually coupled to a gas or steam turbine. Generators are electro-mechanical devices that convert mechanical energy into electricity. These devices consist of an armature placed between magnets. Due to the rotation of the armature, the magnetic flux changes which results in an induced electromotive force (EMF) in the armature. Based on the requirement, the voltage of this generated EMF is increased or decreased by a transformer utility.

Transmission utility

The electric transmission utility consists of generation stations, transmission networks, substations, and distribution systems.

The generation stations are those, where the electricity is produced by the generators. The voltage of the generated electricity is increased by a step-up transformer for long-distance transmission via a network of cables. Before distribution, the voltage is reduced by a step-down transformer and transferred to local customers via distribution systems.

Substations

The substations consist of transformers whose primary task is to reduce or increase the voltage of electricity. The voltage can be altered several times before it reaches the consumers. There are generally three kinds of substations, they are:

• Step-up substation: These are the stations that increase the voltage generated by the generators of power plants. These stations are situated near to a power plant.
• Step-down substation: These stations are situated in the locality where the electricity reaches for consumption. The work of these substations is to reduce the high-voltage to low-voltage.
• Distribution substation: These stations transform the state of the voltage to the required rating which can be utilized for consumption.

Some of the important components of a substation include:

• Circuit breakers: These components account for the safeguard of electrical systems from short circuits and faults.
• Switches: These control the flow of current in the required area and direction.
• Capacitors: These are large and mainly used for power correction factors.

Power distribution lines

The substations are mainly connected to the transmission systems. The transmission systems lower the voltage into medium rated voltage, normally in the range of 2 KV to 35 KV. The transmission lines carry this rated current to the transformers normally located near the consumer's locality. These transformers are known as distribution transformers. These transformers alter the state of the voltage based on the locality requirement and directly transfer the power for consumption.

Grid storage

The grid storage is an arrangement to store the electricity when the production is more than required or plentiful. These contain devices that store electricity and return it to the grid during requirements. The current commonly used storage system includes the use of batteries.

Smart grid

A smart electricity grid is an electrical grid that uses a variety of utilities and operations such as automation, communications, information technology (IT), and so on. These systems use advanced technology that allows professionals to monitor electricity transmission to consumption. It also provides flexibility to control and regulate the power according to required needs. Real-time monitoring and control is also possible in the case of smart power grids. The technology in the smart power grids also allows for real-time fault detection, and with included IT system, it is possible to accurately rectify the faults.

Features of a smart grid

Different features of a typical smart grid include the following:

• Real-time monitoring
• Automated control and system robustness
• In-house display power systems
• Information through internet portals and mobile application
• Efficient energy management
• Live tracking of energy generation and usage
• Uses green energy production techniques

Context and Applications

This topic is widely used in many undergraduate and postgraduate degree courses of:

• Bachelors of Technology (Electrical Engineering)
• Bachelors of Technology (Electrical and Electronics Engineering)
• Master of Technology (Energy Systems)

Practice Problems

Q 1. What are smart grids?

1. It is an automated grid.
2. It provides fault detection and diagnosis.
3. It enables real-time monitoring.
4. All of these

Answer: Option d

Explanation: Smart grid is a fully automated grid that makes use of automation technology. The smart grid allows real-time monitoring with fault detection and diagnosis.

Q 2. Which of the following threats accounts for the largest damage to the power grids?

1. Coronavirus disease 2019 or COVID-19
2. Cyclones
3. Human threats
4. Earthquake

Answer: Option b

Explanation: Cyclones are one of the biggest threats to a power grid which account for maximum damage.

Q 3. Which of the following is a major component of a power generation unit?

1. Switches
2. Generators
3. Turbines
4. Transmission lines

Answer: Option b

Explanation: The generators are the primary component of a power generation unit.

Q 4. What is a step-up substation?

1. It reduces the voltage of the incoming electricity from the power grid.
2. It increases the voltage of the incoming electricity from the power grid.
3. Both a and b
4. None of these

Answer: Option b

Explanation: The step-up substation increases the voltage of the incoming electricity from the power grid.

Q 5. Why are capacitors used in substations?

1. To store electrical charge
2. To increase the voltage
3. To decrease the voltage
4. For the power correction factor

Answer: Option d

Explanation: The main work of capacitors in a substation is to account for the power correction factor.