Power System Protection – Components and Importance

A power system is an interconnected network of electrical components such as alternators, transformers, transmission and distribution lines, and electrical loads.

Each of these components are sensitive to different types of faults or abnormal conditions. For example, a transformer can burn due to overloading or short-circuit. Therefore, it is desirable to implement such systems that can protect these highly expensive electrical equipment from damage.

This practice of implementing protection systems for power system or its components is referred to as power system protection.

In this article, we will explain in detail the components, important terms, and the importance of power system protection in the field of electrical engineering. Let’s get started with the basic definition of power system protection.

What is Power System Protection?

A branch of electrical engineering that deal with the implementation of protection systems for preventing damages to electrical power systems or its components during faults or abnormal conditions is termed as power system protection.

The primary function of the power system protection is to isolate the faulted segment of the power system from rest of the electrical network. Thus, we can say that the main aim of the power system protection is to keep the operation of power system stable by isolating the faulty components from the healthy system.

If we do not use power system protection in our electrical power networks, this can result in an accident or loss of property or life. Under normal operating conditions, we think that power system protection schemes are useless, but we know that the normal operating conditions are not always guaranteed. Therefore, it is always important to implement right power system protection schemes to secure our electrical systems.

Importance of Power System Protection

To understand the importance of power system protection, let us consider a few examples.

Consider an electric motor or any other electrical load component. Under the heavy use, these components/equipment draw a high electric current from the power source. When this current flows in the circuit, the wires and components of the equipment will overheat and may ultimately burn up. Also, the electric power surges or lightening surges can extensively damage the power system equipment and connecting wires.

Also, many electrical and electronic components like transformers have a very low overload withstand capacity as compared to conductors like cables and wires.

Therefore, we have to provide proper protection devices that can sense overload condition at a very fast speed and open the circuit.

To design an efficient protection system, we need to evaluate the load characteristics during starting and at normal operating condition.

Components of Protection System

A typical electrical protection system consists of the following four main components −

• Current and Potential Transformer (CT-PT)
• Protective Relays
• Batteries
• Communication Channels

However, a practice protection system consists of several other auxiliary equipment. But the above four are the main components, so let us discuss about these four components of protection system in detail.

Current and Potential Transformers

The current and potential transformers are used to reduce the high values of currents and voltages of the electrical power system to convenient levels for the relays and measuring instruments.

The current transformer is used for reducing the value of high electric currents while the potential transformer is used for reducing the high value of voltages in the circuit.

Protective Relays

A relay is nothing but an automatically operated electric switch. In electrical protection system, the protective relays are used to sense or detect the fault condition and initiate a trip of the faulty circuit.

The protective relays regularly monitor the current and voltage in the circuit for triggering the circuit breaker to open if a fault or abnormal condition occurs in the circuit.

Batteries

Batteries are one of the important components of the protection system. These are mainly provided to supply electric power in case of power disconnection in the system.

Communication Channels

Communication channels are the modes of transmitting control signals among different parts of the protection system.

In power system protection, communication channels are used to implement remote tripping of the circuit. These also allow to analyze the currents and voltages of the line remotely.

In power system, a communication channel can be a wire or a radio channel.

Important Terms Related to Power System Protection

The following are some important terms related to power system protection and their definitions -

Relay - A relay is an electromagnetic or electromechanical or electronic device that can automatically operate using a power signal to perform the switching of a high-power signal.

Protective Relay - A protective relay is a type of relay that can automatically operate in case of any fault or abnormal condition that occurs in the electrical system. The protective relay is generally used to sense the abnormality and trip the circuit breaker to isolate the faulty section from the healthy section of the system.

Circuit Breaker - A circuit breaker is a type of electrical switch that can operate manually or automatically. It is used in protection system to trip the circuit when a signal is received from the relay. It is the main component of the protection system that separate the faulty and healthy sections of the system.

Pickup Value - It is the threshold value of the actuating quantity like current or voltage above which the relay will operate.

Reset Value - The threshold value of the actuating quantity like current or voltage below which the relay is de-energized and comes to its normal operating condition is known as reset value.

Conclusion

To conclude, Power System Protection is an important concept of electrical engineering that improves the safety and reliability of the electrical power system. It protects the components of power system from unwanted damages due to faults and abnormal conditions.

Power system protection is nothing but an interconnected system of components like relays, circuit breakers, communication channels, etc. which is designed to isolate the faulty part of the system from the healthy part when a fault occurs.

In electrical power systems, the protection system is essential to minimize the risks of equipment damages or loss of life due to accidents.

FAQs Related to Power System Protection

The following are some most commonly asked questions related to the power system protection.

1. What are the protective devices in power system?

Protective devices in power system are the electrical or electronic devices that can detect the abnormal condition in the circuit and initiate tripping of the circuit breaker. The following are some key protective devices used in power system protection -

Protective relays - To sense the fault or abnormal condition in the circuit and initiate the circuit breaker operation.

Circuit breaker - It is an automatically operated electric switch that opens the circuit when a trip signal is received from the relay.

Fuses - It is a protective device which consists of a metal wire that can melt in case when a fault occurs and a high current flowing in the circuit.

Communication channels - It is a network that connects different components of the protection system together and allows for signal transmission.

2. What is need of power system protection?

An electrical power system comprises of several expensive and sensitive equipment like transformer, alternator, measuring instruments, and more.

Faults occurring in the system can damage these equipment and cause a loss of property or life due to electrical accidents. Therefore, an electrical protection system has to be implemented to protect the power system from faults or abnormal conditions.

3. What is fault in power system?

An abnormal condition that affects the normal operation of the electrical system that can result in damage to the system equipment/components is called a fault.

4. What is power system relay?

A relay or power system relay is an electrically operated switch used in power system protection for sensing the faults or abnormal conditions and operate the circuit breaker to isolate the faulty section from the healthy part.

5. What are the goals of protection?

The following are some important goals of using power system protection -

• Protect the equipment from damages,
• Improve the safety of electrical system,
• Enhance the reliability of the power system,
• Reduce the service discontinuity time,
• Optimize the utilization of system equipment, etc.