Electrical Substation Equipment: Lightning Arrester and Its Functions

A Lightning Arrester, also known as a Surge Arrester or Lightning Protector, is an essential piece of electrical equipment used in electrical substations and power systems. Its primary purpose is to protect substation equipment and the power grid from the damaging effects of lightning strikes and transient overvoltages.

Lightning is a natural phenomenon that occurs during thunderstorms when the charge separation in the atmosphere creates a high-voltage electrical discharge between clouds or between a cloud and the ground. When lightning strikes occur, they can induce extremely high voltages and currents in nearby power lines and electrical equipment, posing a significant threat to the power grid's integrity and the equipment connected to it.

A Lightning Arrester acts as a buffer between the power system and the lightning strike. When a surge or overvoltage occurs due to a lightning strike, the arrester provides a low-impedance path to divert the excess energy away from the sensitive electrical equipment. This protective action prevents the voltage from rising to destructive levels and helps to safeguard transformers, circuit breakers, insulators, and other substation components.

There are different types of Lightning Arresters, but the most common ones used in substations are metal-oxide varistors (MOV) and gapped silicon-carbide arresters. Metal-oxide varistors are highly effective and widely used due to their compact size and superior performance. When a voltage surge exceeds a certain threshold, the MOV's resistance drops dramatically, allowing it to shunt the excess current to the ground. This action effectively clamps the voltage at a safe level and protects the connected equipment.

In addition to protecting against lightning-induced surges, Lightning Arresters also guard against switching surges, which can occur during normal operation when switching high-voltage circuit breakers or other devices.

It's important to note that Lightning Arresters have a limited lifespan and can degrade over time due to repeated surges and environmental factors. Regular maintenance and periodic testing are essential to ensure their continued effectiveness in protecting the electrical substation and the power system.

Overall, Lightning Arresters play a crucial role in maintaining the reliability and safety of electrical substations by mitigating the impact of lightning strikes and transient overvoltages. They are an integral part of the overall substation protection and grounding system.

Where do we Connect the Lightning Arresters in an Electrical Substation?

Lightning arresters, also known as surge arresters or lightning protection devices, are essential components in electrical substations to protect equipment and systems from transient overvoltages caused by lightning strikes. The location of lightning arresters in a substation is critical to ensuring effective protection. Here are the typical locations where lightning arresters are connected in an electrical substation:

• Incoming Lines: Lightning arresters are usually installed at the entry points of the substation where the high-voltage transmission lines are connected. These arresters protect the substation equipment from lightning strikes on the overhead lines before the power reaches the substation.
• Transformer Bushings: Transformers are sensitive and expensive equipment in a substation. Lightning arresters are often connected to the bushings of power transformers to safeguard them from lightning-induced surges.
• Busbars: Busbars are the main conductors that distribute power within the substation. Lightning arresters are installed at the busbars to prevent overvoltages caused by nearby lightning strikes.
• Capacitor Banks: Substations often use capacitor banks for power factor correction. These banks are also protected by lightning arresters to avoid damage from lightning surges.
• Switchgear and Circuit Breakers: Lightning arresters are connected to the switchgear and circuit breakers to protect these critical components from lightning-induced overvoltages.
• Outgoing Lines: Similar to the incoming lines, lightning arresters are installed at the exit points of the substation to protect the outgoing transmission lines.

It's essential to have a well-designed grounding system along with lightning arresters to ensure effective dissipation of the lightning energy. Proper placement and connection of lightning arresters play a vital role in safeguarding electrical equipment, reducing downtime, and preventing damage caused by lightning strikes in a substation. It's important to consult with electrical engineers and follow applicable standards and codes to ensure the correct installation and protection of the substation.

Types of Lightning Arresters Used in an Electrical Substation

In electrical substations, various types of lightning arresters, also known as surge arresters, are used to protect electrical equipment from voltage surges caused by lightning strikes or switching operations. These surges can potentially damage or disrupt the operation of sensitive equipment. The primary types of lightning arresters used in electrical substations are as follows:

Rod Gap Arrester: This is the simplest and oldest type of lightning arrester. It consists of two or more metal rods placed in the air with a small air gap between them. When a lightning surge occurs, the voltage across the gap increases, causing the air to break down and create a low-impedance path to the ground, diverting the surge away from the protected equipment.

Horn Gap Arrester: This type is an improvement over the rod gap arrester and is still in use in some older substations. It uses horn-shaped conductors instead of simple rods to enhance the discharge capacity and protect against higher-magnitude surges.

Multi-Gap Arrester: To increase the protection level, multiple gaps can be connected in series or parallel to create a multi-gap arrester. This design offers higher energy absorption capability and is more effective in handling repetitive surges.

Expulsion Type Arrester: This type of arrester uses an arc-quenching mechanism to divert the lightning surge. It contains a series of spark gaps and expulsion materials, usually made of zinc oxide. When a surge occurs, the voltage across the spark gaps ionizes the expulsion material, creating a conducting path that redirects the surge to the ground.

Metal Oxide Varistor (MOV) Arrester: MOV arresters are commonly used in modern electrical substations. They are more compact, have faster response times, and provide superior protection compared to traditional gap-type arresters. MOV arresters use metal oxide discs that have a high resistance under normal conditions but rapidly change to a low-resistance state when a surge is detected, diverting the excess current to the ground.

Hybrid Arrester: A hybrid arrester combines the advantages of both expulsion-type and MOV-type arresters. It uses a MOV block in series with an expulsion gap to offer a more robust and reliable protection solution for substations.

The specific type of lightning arrester used in a substation depends on various factors, such as the voltage level of the substation, the magnitude of surges expected in the region, and the specific requirements of the equipment being protected. Generally, MOV-type arresters are becoming more prevalent due to their superior performance and reliability.

How Does a Lightning Arrester Protect an Electrical Substation?

A lightning arrester, also known as a surge arrester or lightning diverter, is a crucial component used to protect electrical substations and other sensitive electrical equipment from the damaging effects of lightning strikes and transient voltage surges. Here's how a lightning arrester works to safeguard an electrical substation:

Understanding Lightning Strikes: Lightning is a natural phenomenon caused by the discharge of static electricity between clouds or between a cloud and the ground. When a lightning bolt strikes the ground or a nearby object (such as a power transmission line or a substation), it can generate extremely high currents and voltages that can severely damage electrical equipment.

Structure of a Lightning Arrester: A lightning arrester is typically installed at the entrance of the electrical substation. It consists of a robust metal oxide varistor (MOV) or surge arrester blocks connected in parallel with the power line. The MOV is a semiconductor device designed to have a highly nonlinear voltage-current characteristic, allowing it to conduct current rapidly when voltage exceeds a certain threshold.

Normal Operation: During normal operation, when the voltage on the power line is within its standard operating range, the MOV presents a very high resistance, virtually blocking any current flow through the arrester. This ensures that the lightning arrester has a minimal impact on the normal functioning of the substation.

Lightning Strike or Voltage Surge: When a lightning strike or a transient voltage surge occurs, there is a sudden and significant increase in voltage on the power line. The MOV in the lightning arrester detects this overvoltage condition.

Switching to Low Resistance State: When the voltage exceeds the designed threshold, the MOV enters a low-resistance state almost instantly. This allows the lightning arrester to divert the excessive current from the lightning strike or surge away from the substation's sensitive equipment.

Dissipation of Excessive Energy: The lightning arrester provides a low-resistance path to direct the excessive energy safely to the ground. By diverting the dangerous current to the ground, the lightning arrester protects the substation and its equipment from damage.

Recovery to Normal State: After the lightning strike or transient surge event is over, and the voltage on the power line returns to normal levels, the MOV goes back to its high-resistance state, ready to protect the substation from the next potential surge.

In summary, a lightning arrester acts as a sacrificial element that takes the brunt of lightning strikes and transient voltage surges, diverting the dangerous currents away from the sensitive equipment in the electrical substation. By doing so, it helps prevent damage to transformers, switchgear, and other vital components, ensuring the reliable and safe operation of the substation. Lightning Protection Devices for Thundering Protection are discussed in another article.

How Does a Lightning Arrester Sense a Normal Operation and Surge Voltage?

A lightning arrester, also known as a surge arrester or lightning diverter, is a device used to protect electrical systems and equipment from transient voltage surges, such as those caused by lightning strikes or switching operations. Lightning arresters are typically installed on power lines, electrical distribution systems, and sensitive electronic equipment to divert high-voltage surges to the ground, thus preventing damage to the protected devices. 132kV and 33kV Lightning Arrester specifications are discussed in detail in another episode.

The way a lightning arrester senses normal operation and surge voltage depends on its design and technology. There are mainly two types of lightning arresters:

Non-linear resistor type: These are also known as "valve-type" or "gapless" arresters and are commonly used in modern installations.

Spark gap type: These are traditional arresters that consist of spark gaps and are less commonly used today.

The sensing mechanisms are different for each type:
1. Non-linear resistor type:

This type of arrester uses a stack of metal oxide varistors (MOV) or silicon carbide (SiC) to provide protection. MOVs are made of semiconductor materials and exhibit a nonlinear voltage-current characteristic. Under normal operating conditions, when the voltage across the arrester is within the system's rated voltage, the MOV's resistance is high, acting as an insulator, and allowing the normal current to pass through the system.

During normal operation:

The voltage level is within the system's rated voltage, and the resistance of the MOV is high.

The arrester allows the current to pass through the protected equipment with minimal resistance.

During surge voltage (lightning strike or transient surge):

When a high-voltage surge occurs, such as a lightning strike or switching surge, the voltage across the arrester increases rapidly.

The MOV's resistance drops significantly, becoming a highly conductive path to the ground.

The surge current is diverted through the arrester to the ground, protecting the equipment from excess voltage.

2. Spark gap type:

The spark gap type arrester uses spark gaps to provide protection. A spark gap is a physical gap between two electrodes. During normal operation, the voltage across the spark gap is not high enough to ionize the air in the gap, so the gap remains non-conductive.

During normal operation:

The voltage level is within the system's rated voltage, and the spark gap remains non-conductive.

The arrester allows the current to pass through the protected equipment without affecting its operation.

During surge voltage (lightning strike or transient surge):

When a high-voltage surge occurs, the voltage across the spark gap increases beyond its breakdown voltage.

The air in the gap ionizes, and the spark gap becomes conductive.

The surge current is then diverted through the spark gap to the ground, protecting the equipment.

It's essential to note that both types of lightning arresters work by providing a low-impedance path to the ground during surge events, thereby diverting the excess current away from the protected equipment. This helps in preventing damage to the electrical system and ensures the safety of the connected devices. The choice of lightning arrester depends on the specific application and system requirements.

How Do Connect a Lightning Arrester in Lines?

Connecting a lightning arrester to lines involves installing the arrester on the power lines to protect electrical equipment and infrastructure from the damaging effects of lightning strikes. Lightning arresters provide a low-resistance path to the ground for the lightning surge, diverting the excess electrical energy away from the equipment.

Here's a general guide on how to connect a lightning arrester to power lines:

Important Note: Handling electrical equipment and working with power lines can be dangerous and should only be performed by trained professionals. This guide is for informational purposes only and should not be used as a substitute for professional training or expertise.

Select the Appropriate Lightning Arrester:

Choose a lightning arrester suitable for the voltage and type of power lines you are working with. Lightning arresters come in various configurations based on the system voltage (e.g., 11kV, 33kV, 132kV, etc.). Select a high-quality arrester that meets the requirements of your power system.

Locate the Installation Points:

Identify the locations on the power lines where you want to install the lightning arresters. These points are typically at the entry points of equipment or substations where you want to protect against lightning surges.

Prepare the Installation Site:

Ensure that the installation site is safe and accessible. If necessary, de-energize the power lines and follow all safety protocols before beginning work.

Mounting the Lightning Arrester:

Depending on the type of lightning arrester and power line configuration, mount the arrester using appropriate hardware and equipment. The arrester is usually attached to the supporting structures of the power lines. Follow the manufacturer's instructions for proper installation.

Grounding the Arrester:

Lightning arresters work by providing a low-resistance path to the ground. It is crucial to establish a proper grounding system for the arrester. Connect the ground terminal of the lightning arrester to a reliable and well-designed grounding electrode system.

Check the Connections:

Ensure all connections are tight and secure. Loose connections can lead to the inefficiency of the lightning arrester or pose safety risks.

Testing and Commissioning:

Once the installation is complete, the lightning arrester should be tested to verify its functionality and effectiveness. Work with the appropriate test equipment and follow testing procedures as per relevant standards.

Regular Maintenance:

Lightning arresters should be regularly inspected and maintained as per the manufacturer's guidelines. Regular maintenance helps ensure that the arrester continues to perform its intended function effectively.

Remember, working with power lines and electrical equipment is hazardous, and improper installation of lightning arresters can lead to serious consequences. It is essential to seek professional guidance and assistance from qualified personnel when dealing with such installations.

Is There a Difference Between Lightning Arrester and Surge Arrester?

The terms "lightning arrester" and "surge arrester" are often used interchangeably, but there is a subtle difference between the two. Both devices are designed to protect electrical systems and equipment from sudden voltage spikes or surges, but they primarily serve different purposes.

Lightning Arrester:

A lightning arrester is specifically designed to protect electrical systems from lightning-induced voltage surges. Lightning strikes can produce extremely high voltage surges that can cause significant damage to sensitive electronic equipment, electrical appliances, and power distribution systems. A lightning arrester's primary purpose is to divert the lightning surge to the ground, thus protecting the equipment downstream from the full impact of the lightning strike.

These devices typically consist of a series of metal rods or other conductive elements mounted on top of structures (such as buildings or utility poles) and connected to the ground. When lightning strikes the structure, the lightning arrester provides a low-resistance path for the electrical energy to flow directly into the ground, bypassing the protected equipment.

Surge Arrester:

On the other hand, a surge arrester is a broader term that refers to devices used to protect electrical equipment from voltage surges caused by various sources, not just lightning strikes. Surges can occur due to internal causes like switching off electrical appliances or external causes like lightning, power grid disturbances, or faults in the power system.

Surge arresters are installed at various points within the electrical distribution system to detect and divert overvoltage surges to the ground. They typically contain metal oxide varistors (MOV) or other semiconductor components that have high resistance at normal operating voltages but become highly conductive when voltage exceeds a certain threshold. This characteristic allows them to absorb and dissipate the surge energy, protecting the connected equipment.

In summary, while the terms "lightning arrester" and "surge arrester" are often used interchangeably in common parlance, the main difference lies in their scope and intended application. A lightning arrester specifically protects against lightning-induced surges, while a surge arrester provides protection against a broader range of voltage surges from various sources. The difference between Lightning and Surge Arrester is discussed in a separate episode.

How Does a Lightning Arrester Absorb a Lightning Strike?

A lightning arrester works on the principle of providing a low-resistance path for the excess electrical energy to flow safely to the ground, bypassing the equipment it is meant to protect. Here's how it absorbs a lightning strike:

• Metal oxide varistor (MOV): Most modern lightning arresters use a component called a metal oxide varistor or MOV. This is a ceramic-based device with zinc oxide grains that exhibits a non-linear voltage-current characteristic. Under normal operating conditions, the MOV has a high resistance and does not conduct electricity.
• High voltage threshold: When a lightning strike or surge occurs, it creates a sudden and massive increase in voltage. When the voltage exceeds a certain threshold value, the MOV's resistance decreases dramatically, becoming highly conductive.
• Diverting the surge: As the MOV becomes conductive, it provides a low-resistance path to divert the excess electrical energy from the lightning strike or surge. This path leads the energy directly to the ground rather than allowing it to flow through the sensitive equipment.
• Grounding: For the lightning arrester to effectively dissipate the energy, it must be connected to a reliable grounding system. The grounding ensures that the electrical energy safely travels down to the earth, where it can be harmlessly dispersed.
• Absorbing the energy: The lightning arrester absorbs the energy of the lightning strike or surge, protecting the connected equipment from experiencing the full force of the electrical surge.

It's essential to note that while a lightning arrester can protect against many electrical surges, it may not be able to handle extremely powerful or direct lightning strikes. In some cases, lightning rods or more robust lightning protection systems are used to mitigate the risk further.

In summary, a lightning arrester absorbs a lightning strike or surge by providing a low-resistance path to divert the excess electrical energy to the ground, protecting the connected equipment from damage.

Lightning Arrester LifeTime

The lifetime of a lightning arrester can vary depending on several factors, including the type of arrester, its quality, the environmental conditions it is subjected to, and how frequently it has to protect against lightning strikes or electrical surges. Generally, well-maintained and good-quality lightning arresters can have a lifespan of 10 to 20 years or even more.

Some of the factors that can affect the lifespan of a lightning arrester include:

• Quality: Higher-quality lightning arresters tend to have longer lifespans as they are designed to withstand multiple surge events.
• Type of arrester: There are different types of lightning arresters, such as surge arresters for power lines, communication lines, buildings, and equipment. Each type may have a different lifespan.
• Environmental conditions: Harsh environmental conditions, such as high humidity, extreme temperatures, and exposure to corrosive substances, can reduce the arrester's lifespan.
• Frequency of surges: Frequent lightning strikes or electrical surges can degrade the arrester's performance over time.
• Maintenance: Regular inspection and maintenance can help prolong the arrester's lifespan and ensure its effectiveness.

To ensure the continued protection of electrical and electronic systems, it is essential to monitor and replace lightning arresters when they reach the end of their expected lifespan or show signs of deterioration. Consulting the manufacturer's guidelines and recommendations can provide more specific information about the expected lifetime of a particular lightning arrester model.

Substation-related major equipment is discussed in another episode.