Faults in Electrical Power Systems – Causes and Effects

In the field of electrical engineering and power systems, a fault is an abnormal condition that can result in damages to the circuit. Hence, a fault is nothing but a defect in the power system.

When a fault occurs in a power system, we need a "power system protection" scheme that can isolate the faulty part from the healthy part.

In this article, we will learn about basic definition of a fault in power system, its main causes and effects. So, let’s get started with the basic definition of the electrical fault in power system.

What is a Fault in a Power System?

In a power system, a fault is a defect or an abnormal condition that occurs in the circuit and can cause damages to it.

When a fault occurs in the power system, there can be any abnormal flow of electric current in the circuit. For example, a short-circuit is a common electrical fault that is an unwanted path of low resistance which bypasses the normal load circuit.

On the hand, an "open circuit" is another common fault that occurs in the power system. An open circuit fault occurs when there is an interruption or a gap in the circuit.

In practical power systems, several different types of faults occur like like three-phase fault, ground or earth fault, line-to-line fault, and more.

In power systems, electrical protective devices are used to detect fault conditions and open the circuit breakers to limit the losses due to flow of abnormal currents.

The following figure depicts a line-to-ground short-circuit fault in a distribution line.

Causes of Faults in a Power System

In an electrical power system, faults can occur due to many reasons. Some of the common reasons behind the occurrence of faults in power system are explained below.

Insulation Failure

An insulation failure is one of the major reasons behind the occurrence of faults in a power system. The following are some primary causes that promotes the insulation failure −

• Overstressing of insulation
• Degradation of insulation over time
• Corrosive vapors
• Excessive hot or cold conditions
• Moisture and dirt
• Vibrations, etc.

To prevent the faults due to insulation failure, different maintenance tests are performed to assess the quality of insulation and replace it if needed.

Short Circuits

A short-circuit is an undesirable path of very low resistance that allows a very large current to flow through it and results in overheating and electric fire.

Short-circuit is one of the dangerous conditions that can damage the equipment of power systems.

When a short-circuit occurs in an electrical network, the following consequences are generally seen -

• Overheating of conductors
• Electrical fire or explosion
• Circuit damage, etc.

Overvoltage Condition

When the voltage in the power system circuit becomes greater than its maximum specified limit, then it is called overvoltage.

Overvoltage condition may be very hazardous depending on its duration. As it can cause insulation breakdown, excessive current flow, overheating, electric fire or explosion, etc.

The primary reasons behind the overvoltage condition are -

• Lightening surges
• Switching surges
• External conducting objects
• Electrical resonance
• Industrially induced shock voltages, and more.

Dust Particles

A layer of dust particles is stick on the surface of insulators that reduces the insulation strength and can cause short circuits in the power system.

Faults due to Broken Conductors

When a line conductor is broken, then an open circuit condition arises which is a type of fault in power system.If the broken conductor falls on the ground, this causes a short-circuit or ground fault.

In most practical cases, the fault due to broken conductor results in a short circuit fault between two phases, one phase and ground, or two-phases and ground. When this fault occurs, a flashover initiate.

The major reasons behind the faults due to broken conductors are -

• Physical damages dur to environmental factors, human work, fall of trees, vehicle accidents, etc.
• Overheating due to flow of overload current
• Mechanical stress due to vibrations, bending, etc.
• Aging of the conductor, etc.

Miscellaneous Causes of Faults

Apart from the above discussed causes, faults in power systems can also occur due to the following reasons -

• Short-circuits due to animals and birds interference/contact with the wires
• Malfunctioning of electrical equipment
• Human errors in operations and maintenance work of power system
• Snow loading, storms and earth quakes, etc.

From the above discussion, we can list out the major causes of faults in power systems for a quick review as follows -

• Insulation failure
• Conduction path failure
• Overvoltage condition
• Deposition of dust particles on insulators
• Animal or birds contact with lines
• Falling trees on power lines
• Broken conductors
• Direct lightening strokes
• Abnormal loading of the power lines
• Mechanical damages
• Poor quality material used in power system
• Environmental causes like earth quakes, storms, heat, ice or snow loading, etc.

Effects of Faults in Power System

In power systems, faults have several effects that can impact the reliability, stability, efficiency, and safety of the overall system. Some of the major effects or consequences of faults in power system are listed below -

• Faults like short-circuit or overvoltage can damage the equipment connected in the system.
• Faults can cause arching, electric fire, or explosion.
• Faults can also result in voltage instability or voltage fluctuations.
• Due to faults, overvoltage or low voltage conditions can occur in the power system.
• Faults cause the supply interruption and power outages.
• Faults also results in high maintenance cost and increased down time.

These are some major effects commonly seen in the case of faults in power system.

Minimization of Effects of Faults in Power System

Faults in power system are undesirable conditions that impose higher maintenance cost, increased downtime, and reduced reliability and stability of the power system. Therefore, it is a must practice to minimize the chances of fault occurrence. Some of the key practices that we should implement to minimize the effects of faults in power system are listed here -

• We have to use high quality material and equipment.
• We must implement a highly effective protection system.
• We must do regular, time-to-time maintenance and testing of the system.
• We have to continuously monitor the power system for faults.
• We should not overload the power lines.
• Implement smart grid technology and advanced protective devices.
• We should implement automatic fault detection isolation systems to separate faulty part from rest of the healthy system.
• We should try to synchronize all components of the power system to maintain the power system stability.

By following these some common practices, we can significantly minimize the effects of faults in power system.

Conclusion

In this article, we explained in detail about different types of faults in electrical power systems and their effects. Here we covered the basic meaning of a fault in a power system along with is main causes, effects, and practices to minimize the effects.

In conclusion, we can state that a fault is an abnormal circuit condition that impacts the stability, reliability, and safety of the power system. Therefore, it is advisable to implement proper protection system and maintenance practices to minimize the changes of faults and their effects on the system and its components.

FAQs Related to Faults in Power Systems

The following are some commonly asked questions and their answers related to faults in power systems.

1. What are the 4 types of electrical faults?

The following are the 4 main types of electrical faults that occur in a power system -

Short Circuit Fault - When two conductors are connected together to create an undesirable path of very low impedance and results in excessive current flow or bypass of the normal load circuit, then it is called a short circuit fault.

Open Circuit Fault - When there is a broken connection or interruption in the circuit that prevents the flow of current is referred to as open circuit fault.

Ground Fault - When a live line conductor comes in contact with the earth or ground and results in a short-circuit or heavy current flow from conductor to ground, then it is called a ground fault.

Line-to-Line Fault - When two conductors of a transmission or distribution line comes in contact with each other and cause a short-circuit, it is called a line-to-line fault.

2. What is phase to phase fault?

In a three-phase or polyphase electrical system, when two phase conductors touch each other and results in a short-circuit, then it is called a phase-to-phase fault. This fault is a very common fault in three-phase electrical systems. The major reasons behind this fault are insulation failure or malfunctioning of equipment.

3. What is a fault example?

When a conductor is broken and comes in contact with the ground surface is a common example of fault in power system.

4. What is transient fault?

A transient fault is a type of temporary fault which occurs when a lightening or switching surge comes into the system. This fault has an ability to automatic restoration after a short period of time.

5. What is a Feeder Fault?

A feeder is a conductor that connects a source like a substation to a distribution network. When there is any abnormality like open-circuit, short-circuit, etc. in the feeder, then it is called a feeder fault.