Understanding Surge Arresters: Definition, Types, and Function

A surge arrester, also known as a surge protector or lightning arrester, is a device designed to protect electrical equipment from voltage spikes or transient overvoltage. These spikes can be caused by various factors, such as lightning strikes, switching operations in the electrical grid, or other electrical disturbances. The primary purpose of a surge arrester is to divert excess voltage and current away from sensitive equipment, preventing damage and ensuring the proper functioning of electrical and electronic devices.

Surge arresters are commonly used in electrical systems to protect equipment like computers, televisions, appliances, and other sensitive electronics.

The basic construction of a surge arrester typically involves a metal oxide varistor (MOV) component. Surge arresters are commonly installed at various points in an electrical system, including at the entrance of buildings, in power distribution panels, and on individual devices. They play a crucial role in safeguarding electronic equipment and preventing downtime or damage caused by transient overvoltages.

Surge Arrester Construction

The figure depicts components inside a typical surge arrester. Surge arresters typically consist of a few key components, with the most common type utilizing a metal oxide varistor (MOV) or resistor as the primary element.

The MOV is enclosed in a housing made of insulating materials to provide electrical isolation and protection. The housing contains a spark gap and other components.

Surge Arrester Types

There are two main types of surge arresters: station-class and distribution-class.

• Station-Class Surge Arresters: These are typically used in high-voltage power systems, such as substations. They have higher energy-handling capabilities and are designed to protect the overall substation equipment.
• Distribution-Class Surge Arresters: These are used in medium and low-voltage systems to protect distribution transformers and other equipment. They have a lower energy-handling capacity compared to station-class arresters.

Surge Arrester Working Operation

Let’s understand how a surge arrester works in normal and over-voltage conditions.

The working principle of a surge arrester involves its ability to rapidly change its impedance in response to voltage changes.

• Normal Operation: During normal operation, the MOV has a high impedance, allowing it to block the flow of current at typical operating voltages.

• Voltage Surge: When a voltage surge occurs, such as due to lightning or switching events, the voltage across the surge arrester increases. As the voltage surpasses a certain threshold, the MOV’s impedance decreases, allowing it to conduct and divert the excess current to the ground.

  In conjunction with the MOV, the spark gap also activates, providing an additional path for the surge current to flow to the ground.

• By conducting the surge current to the ground, the surge arrester protects connected equipment from the damaging effects of overvoltage.

Advantages of Surge Arrester

Following are the benefits or advantages of Surge Arresters:

1. It has the ability to protect electrical and electronic equipment from damage caused by voltage surges.
2. Surge arresters provide a reliable and effective means of diverting excess voltage to the ground, ensuring that connected equipment operates within safe voltage limits.
3. By preventing damage to equipment, surge arresters help minimize downtime and maintenance costs associated with the replacement or repair of damaged devices.
4. The use of surge arresters can lead to cost savings by avoiding the need for frequent repairs or replacements.
5. Voltage surges can potentially lead to overheating and fires in electrical systems. Surge arresters help mitigate this risk.
6. By preventing damage caused by surges, surge arresters contribute to the extended lifespan of the equipment.
7. It offers protection against lightning strikes.
8. Surge arresters are versatile and can be applied in various settings, including residential, commercial, industrial, and infrastructure applications.

Disadvantages of Surge Arrester

Following are the limitations or disadvantages of Surge Arresters:

1. Surge arresters have a specific energy-handling capacity. Hence, they may not be suitable for very high energy surges.
2. Over time, surge arresters may experience aging and degradation, reducing their effectiveness.
3. The response time of surge arresters is critical. If the arrester doesn’t activate quickly enough, some level of damage may occur before the excess voltage is diverted.
4. Depending on the application and the type of surge arrester used, there may be space requirements for installation, especially in crowded electrical panels or equipment rooms.
5. Surge arresters can be affected by environmental conditions such as extreme temperatures, humidity, or corrosive atmospheres. Hence, choose the right surge arresters as per the specific environmental conditions of the installation site.

Conclusion

In summary, while surge arresters provide crucial protection against voltage surges, it’s important to consider their limitations and ensure proper selection, installation, and maintenance to maximize their effectiveness.